Flint Corn in Zone 9 -- plant

Subzone	Last spring	First fall	Growing days	Winter min	Fruits reliably
9a	Mar 8	Nov 24	~261	20-25°F	Yes · two seasons
9b	Feb 28	Nov 30	~275	25-30°F	Yes · two seasons

Beginner

Know your soil

Your soil

Identify yours

Not sure what soil you have? Grab a small handful of damp soil from your garden bed and squeeze it. If it crumbles apart easily, it's sandy. If it holds together but breaks when you poke it, it's loam (what most vegetables want). If it stays in a hard, slippery ball, it's clay.

What this crop wants

Corn likes deep, rich, well-drained soil. If water pools on your bed after rain, work in compost and consider a raised bed so the roots never sit wet.

If your soil doesn't match

You have sandy soil

Mix 2-3 inches of compost into the top 6 inches of your bed before planting. Compost holds moisture (which sandy soil drains too fast) and adds the nutrients sandy soil tends to lack. Repeat each season. Compost breaks down over time.

You have clay soil

Mix 2-3 inches of compost AND a few inches of coarse sand or perlite into the top 6 inches of your bed. The compost feeds the plants; the sand breaks up the clay so air and water can move through. Don't add sand without compost. It can compact like concrete.

Containers and raised beds

If amending your soil sounds like too much work, or if your soil is heavy clay, full of rocks, or contaminated, build over it. A raised bed at least 12 inches deep filled with a 50/50 mix of compost and sandy loam gives you ideal growing soil with no battles. A 5-gallon container with quality potting mix does the same for one plant at a time. Both bypass your native soil entirely.

Learn more about your soil

The specs

Care guide

The numbers that matter, at a glance.

Sunlight

Full sun · 6-8 hrs/day

Water

high

Spacing

8 to 12 inches

Days to maturity

90-110 days from transplant

Soil pH

6 to 6.8

Container OK?

Germination temp

60-90°F

In a pot

Not suited to a pot

Flint corn is not suited to pots. It grows tall, feeds heavily, and must be planted in a block of several plants for wind pollination, so it belongs in a garden bed, not a container.Flint corn is a poor container crop: it is tall and hungry and depends on a block planting for wind pollination, none of which a single pot supports. Grow it in the ground.

Soil chemistry

Soil pH for flint corn

Preferred

6 to 6.8

Tolerated

5.5 to 7

Corn does best in soil that is slightly acidic to neutral, around a pH of 6.0 to 6.8. Most garden beds are already close; a soil test is the only way to know for sure and to catch soil that is too acidic.A soil pH of 6.0 to 6.8 suits flint corn. Lime an acidic bed to reach that range the season before, and confirm both pH and fertility with a soil test, since corn's heavy feeding rewards a well-limed, well-fed bed.

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Steady hand on the hose

Watering

When & how much

Frequency

Water regularly so the soil stays evenly moist. Pay the closest attention from the time the tassels appear through when the ears are filling out, which is when corn needs water the most.Water regularly to keep the root zone evenly moist through the season, with the highest demand from tasseling through silking and ear fill.

Amount

Aim for about 1 inch of water a week, and closer to 1.5 inches while the corn is pollinating and filling ears. Water deeply so it soaks down to the roots rather than just wetting the surface.About 1 inch of water per week from rain and irrigation, rising toward 1.5 inches per week across the pollination and ear-fill window; water deeply to wet the full root zone.

Method

Give corn a deep soak rather than frequent light sprinkles. Corn handles overhead watering better than many crops, but watering at the base wastes less and keeps the leaves drier.Deep soaking at intervals suits corn. Overhead watering is tolerated far better than on disease-prone crops, but soaker or furrow watering conserves water and keeps the canopy from staying wet.

Signs of trouble

Too much water

If the soil stays soggy and the lower leaves yellow while the plant stalls, the roots are drowning. Ease off and let it drain.Yellowing lower leaves and stunted, stalled growth in ground that stays wet point to waterlogged, oxygen-starved roots.

Too little water

Leaves that roll up like tubes in the afternoon mean the corn is too dry. If this happens while the tassels and silks are out, you get ears with missing kernels, so keep the water steady then.Leaves that roll or curl at midday, especially near tasseling, signal drought stress; stress in the silking window desiccates silks and pollen and leaves gappy, poorly filled ears.

Feeding rhythm

Feeding

Frequency

high

Type

nitrogen-forward, sidedressed

When to start

starter at planting; sidedress at knee-high and again at tasseling

Corn is hungry, especially for nitrogen. Mix a balanced fertilizer into the soil at planting, then feed again when the plants are about knee-high and once more when the tassels appear at the top. Those are the times corn needs the most food. In sandy soil or after heavy rain, feed a little more often, since the nitrogen washes away.Corn is a heavy nitrogen feeder. Work a balanced starter into the bed at planting, then sidedress nitrogen twice: once when plants are knee-high and again as the tassels form, the two windows when demand peaks. Sandy soils and heavy rain leach nitrogen, so split the sidedressing further where that applies.

Nitrogen-forward

Corn wants plenty of nitrogen. Use a balanced fertilizer at planting, then feed nitrogen again as it grows.Nitrogen-forward feeding: a balanced starter, then nitrogen sidedressings at knee-high and tasseling.

Who grows well together

Companion planting

Corn is the tall centerpiece of the classic Three Sisters planting with beans and squash. The beans feed the soil the corn is so hungry for, and the squash shades the ground below. Keep corn away from tomatoes, since the two share the same ear-and-fruit worm. Corn anchors the traditional Three Sisters trio: beans climb it and fix nitrogen for its heavy demand, and squash sprawls below as a living mulch. The main caution is tomatoes, which share the pest Helicoverpa zea (corn earworm / tomato fruitworm), so a shared planting can concentrate it.

Other

Beans

The Three Sisters partner: beans pull nitrogen from the air and enrich the soil for hungry corn, and can climb the stalks.Pole beans use the cornstalk as a living trellis and fix nitrogen that offsets corn's heavy demand; the pairing is the well-documented Three Sisters polyculture. The benefit is soil-and-structure rather than a measured pest effect. Traditional

Squash

The third Sister: its big sprawling leaves shade the soil around the corn, holding moisture and smothering weeds.Squash rounds out the trio as a ground-covering living mulch that shades soil, conserves moisture, and suppresses weeds around the corn. A soil-and-space benefit; give it room so it does not swamp young corn. Traditional

Keep apart from

Tomatoes Corn and tomatoes are hit by the same worm, called the corn earworm on corn and the tomato fruitworm on tomatoes, so growing them together can build it up.Corn and tomato share Helicoverpa zea (corn earworm on corn, tomato fruitworm on tomato). Interplanting gives the pest two sequential hosts in one spot, so separating them limits the buildup. Well-grounded

Provenance tagged inline · see methodology for the labeling system Key

Harvest signals

When to pick

Flint corn is ready to harvest when the whole ear has dried down on the stalk: the husks have turned brown and papery, the silks are long dead, and the kernels are hard, smooth, and glassy, not soft or milky. Press a thumbnail into a kernel and it should barely mark. Unlike sweet corn there is no rush, so in good weather you can leave the ears to dry further on the plant. Then pick them, pull back the husks, and finish drying them indoors before you shell off the kernels.Harvest at full physiological maturity and beyond, when the husks are brown and papery, the kernels are hard and glassy (flint kernels harden smooth, without denting), and a black layer has formed at the kernel base (about 30 to 35 percent kernel moisture at that point). For storage the grain needs to reach roughly 13 to 15 percent moisture, so leave sound ears to field-dry on the stalk in dry weather, or pick once the kernels are hard and finish drying them under cover. There is no narrow window as with milk-stage sweet corn.

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Yield

What to expect

Each plant gives about one or two ears of dry grain. A 10-foot row in your block yields roughly a dozen to two dozen dried ears, which comes to a few pounds of kernels once you shell them off the cobs for grinding.Each stalk yields one to two mature ears of dry grain. Home plantings are measured in ears rather than bushels: a 10-foot block row returns roughly a dozen to two dozen dried ears, which shell out to a few pounds of grain for grinding.

There is no rush like there is with sweet corn. The whole block dries down together in fall, you bring it in once, and the dry grain keeps for years, so you harvest it all at once instead of checking it every day.Unlike sweet corn there is no fleeting peak. The whole block matures and dries down together over a few weeks in fall, and the dry grain then keeps for years, so the harvest is a single event rather than a race against the milk stage. Flint corn is not hard to grow, but it needs room and time: a block of several rows and a long, warm season of 90 to 110 days to dry down. The payoff is an easy harvest with no daily checking, and dry grain that stores for years.Flint corn is easy to grow but demands space, a long season, and patience: it needs a block of several rows for pollination and a full 90 to 110 days to dry down. Its great advantage over sweet corn is a forgiving, one-shot harvest and grain that stores for years.

What changes yield

Block planting for wind pollination (a single row or a few plants pollinates poorly and gives gappy ears)Steady moisture at tasseling and silking (the critical window; drought here is the largest yield loss)A long enough frost-free season to reach dry-down (90 to 110 days; the limiting factor in short-season and desert regions)Nitrogen supply (corn is a heavy feeder; short nitrogen limits ear fill)Dry weather at the finish (humid regions may need the ears pulled at the hard, glassy stage and dried under cover)

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Pick your variety

Recommended varieties

Pick a flint by how long your season is and what you want from it. Painted Mountain is the fast, tough choice for short or cold summers, ripening in about 85 days; Roy's Calais and Cascade Ruby-Gold are other early flints good for cornmeal and polenta, while the Italian Floriani Red Flint takes a bit longer, around 100 days. Glass Gem is grown mostly for its gorgeous rainbow kernels. Whatever you plant, keep flint corn away from sweet corn and popcorn so their pollen does not cross and spoil either crop.Flint corn choice turns on season length and use. For short or cold seasons, Painted Mountain (about 85 days) and other early flints like Roy's Calais or Carol Deppe's Cascade Ruby-Gold reach hard grain quickly; the Italian polenta flint Floriani Red Flint runs a bit longer at about 100 days. Ornamental flints like Glass Gem are grown chiefly for their color. Whichever you grow, keep it isolated from sweet corn and popcorn, and from other corn types, since stray pollen crosses the kernels and muddies flint colors.

Painted Mountain

A short-season, cold-hardy open-pollinated flint developed for northern and high-elevation gardens, with 6- to 7-inch ears of gold, orange, red, and purple kernels. It reaches dry grain in roughly 85 days and tolerates cold spring soil better than almost any other corn, so it is the reliable choice where the season is short. Grind it into cornmeal or flour.

Glass Gem

An ornamental flint, sometimes classed as a small-kerneled popcorn type, prized for translucent kernels that shine like glass in a rainbow of colors. It needs a longer season, about 105 to 110 days to hard, glassy ripeness, and is grown mainly for decoration, though the kernels can be popped or ground. Cure the dried ears for several weeks before storing.

Roy's Calais Flint

A classic Northeastern heirloom flint grown for cornmeal and polenta, maturing in about 85 to 95 days with hard, glassy kernels. A New England staple flint and the parent of Carol Deppe's early Cascade Ruby-Gold. Let the ears dry fully on the stalk, then shell and grind.

Off the vine

Storing your harvest

Room temp

Once the kernels are fully dry and shelled off the cob, flint corn keeps like any dry grain. Store it in a sealed jar somewhere cool and dry. Make sure it is thoroughly dry first, or it can mold in storage.Fully dried, shelled flint corn is a dry grain and stores at room temperature. Keep the shelled kernels in an airtight container in a cool, dry, dark place once they reach about 13 to 15 percent moisture; grain that is not fully dry will mold or attract insects.

Fridge

You do not need to refrigerate dry corn, but putting the shelled kernels in the fridge or freezer for a few days first is a good way to kill any tiny insects before you store it.Refrigeration is not needed for dry grain, but chilling or freezing the shelled kernels for a few days is a simple way to kill any weevils or grain-moth eggs before long-term storage.

Freezer

The freezer is the best place to keep shelled corn for a long time. It stays good and stays bug-free. Grind it into cornmeal only when you need it, because whole kernels last much longer than ground meal.For long keeping, store shelled, fully dry kernels in the freezer, which preserves quality and prevents insect damage. Grind to meal only as needed, since whole grain keeps far longer than ground meal.

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When something goes wrong

Common problems

Ears with bare patches and missing kernelsEars with gaps and missing kernels

01 of 04

What happened The ears came out with bare patches because those silks never got pollinated. This usually happens when the corn was planted in too small a group (a single row or a few plants), or when heat or dry soil during silking ruined the pollen and dried up the silks.The ears filled unevenly with blank patches because pollination failed on those silks. The usual causes are a too-small planting (a single row or a few plants), heat over 95°F or drought during silking that killed pollen and dried the silks, or silks that were never dusted because the block was too sparse. Next season Plant a block of at least four short rows so the wind can pollinate well, and keep the water steady while the tassels and silks are out. Try to time it so silking is not in the hottest part of summer, and in a small patch you can gently shake the tassels at midday to spread pollen.Plant a BLOCK of at least four short rows so wind pollination is thorough, and keep moisture high and steady through tasseling and silking. Time plantings so silking misses the worst summer heat, and hand-shake the tassels at midday in a small planting to help.

Seeds rotted or came up thin and patchySeed rotted or came up in a thin, patchy stand

02 of 04

What happened The seed went into soil that was too cold and wet, so it rotted or was damaged by the cold in the first day or two instead of sprouting.The seed was sown into soil that was too cold and wet, so it sat and rotted or suffered chilling injury in the first day or two after sowing instead of germinating. Next season Wait until the soil has warmed to at least 60°F, since planting early only rots the seed. Plant into warm, well-drained soil instead of a cold, wet spot, and do not keep the seedbed soggy.Wait until soil is at least 60°F at sowing depth; there is no benefit to early sowing. Plant into warm, well-drained ground rather than a cold, wet spot, and do not over-water the seedbed.

Ripe ears eaten overnightRipe ears stripped overnight

03 of 04

What happened The ears were torn open and eaten and the stalks knocked over as the corn filled out. Raccoons (and sometimes deer or birds) raid corn once the kernels start to fill and can clear a small patch in a night or two.The ears were pulled down, husked, and eaten and stalks knocked flat as the kernels filled. Raccoons (and sometimes deer or birds) raid corn from the milk and dough stages on and can strip a small patch in a night or two. Next season The sure fix is to keep them out. Set up a short two-wire electric fence and turn it on before the ears fill out, not after the first raid, because once raccoons find your corn they come back every night.Exclusion is the reliable defense: put up a two-wire electric fence (about 4 and 8 inches high) and energize it BEFORE the ears fill out, since once raccoons find the patch they return nightly.

Ears molded or would not dryEars molded or never dried down

04 of 04

What happened The ears did not dry out properly, or grew moldy, because cool, wet, humid fall weather or an early frost caught the crop before the kernels were fully hard. Corn barely dries in cold, damp weather, and ears that were not mature enough tend to mold instead of curing.The ears failed to dry to a storable moisture, or grew mold on the cob, because the crop ran into cool, wet, humid fall weather or a killing frost before it reached the hard, glassy stage. Field-drying stalls below the mid-50s°F and in persistent damp, and immature ears mold rather than cure. Next season Pick an earlier flint variety that fits your season and sow as soon as the soil is warm, so the corn matures with time to spare before fall. In humid areas, bring the ears in at the hard, glassy stage and finish drying them indoors with a fan instead of leaving them out in damp weather.Choose an earlier flint variety matched to your season, sow as early as warm soil allows so the crop black-layers with margin before fall, and in humid regions pick the ears at the hard, glassy stage and finish drying them indoors with airflow rather than leaving them out in the wet.

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The usual suspects

Pests & diseases

Pests

Corn earworm

P · 01

Symptoms A fat, striped caterpillar tunneling into the tip of the ear under the husk, leaving chewed kernels and dark droppings. It usually stays near the tip, but the damage can let mold in.Chewed, frass-fouled kernels at the ear tip where a fat, striped caterpillar has fed under the husk; silks may be clipped, and tip damage opens the door to mold. Cause The corn earworm, a caterpillar whose moth lays eggs on the silks. The young caterpillars crawl down the silks into the ear. It is the same pest as the tomato fruitworm.The corn earworm (Helicoverpa zea), whose moths lay eggs on fresh silks; the hatching larvae follow the silks down into the ear tip. It is the same species as the tomato fruitworm. Organic treatment The good news is the worm usually stays at the very tip, so you can just cut that part off. A classic trick is a few drops of vegetable or mineral oil on the silks after they have been pollinated, and an organic spray such as Bt or spinosad works if you time it to fresh silks.Because most feeding is confined to the ear tip, the loss is often cosmetic: cut off the damaged tip at the kitchen. A few drops of mineral oil applied to the silk channel after pollination is a traditional home tactic; a spinosad or Bt product timed to fresh silks is the labeled organic option. Prevention Pick varieties with long, tight husks that make it harder for the worm to get in, and plant early so the ears silk before the moths are at their worst in late summer.Choose varieties with tight, long husk cover, which slows the larvae, and plant early so the crop silks before peak moth flights in late summer.

The control ladder

The ladder troubleshoots from the gentlest solution to the strongest. Start with the gentlest option and only move on when and if it doesn't work.

Resistant varieties

Start at the seed packet. Varieties with long, tight husk cover make it harder for the young caterpillars to work their way down into the ear. It slows them rather than shutting them out, so treat it as a head start.Husk cover is the varietal lever: long, tight husks slow larvae moving down the silk channel toward the tip. It reduces entry rather than preventing it, so keep the later rungs available.
Bacillus thuringiensis (Bt)

Bt is a naturally occurring bacterium sold as a spray that sickens young caterpillars once they eat it. It helps only if you put it on fresh silks, because that is where the eggs hatch and where the tiny caterpillars feed before they get down inside the ear.Bt is a labeled organic option for the exposed window on fresh silks. Once larvae are down the silk channel they are out of reach, which makes silk timing the whole of the decision.
Spinosad

Where earworm pressure is heavy, spinosad is the stronger organic spray, and like Bt it has to land on fresh silks to reach the caterpillars before they tunnel in.Spinosad is the other labeled organic material for silk-stage treatment, under the same timing constraint as Bt, since neither reaches larvae already feeding inside the ear.

The bottom rungs are products with label rules: timing, pollinators, and days to wait before harvest. Before you spray →

European corn borer

P · 02

Symptoms Tiny holes in the young leaves, then sawdust-like droppings where the leaves meet the stalk, and small holes bored into the stalk itself. Badly tunneled stalks can break.Small shot-hole feeding in the whorl leaves, then sawdust-like frass at leaf axils and pin-sized entry holes in the stalk and ear shank; tunneled stalks weaken and can snap. Cause The European corn borer, a caterpillar that starts by chewing the young leaves, then tunnels into the stalks, hollowing them out.The European corn borer (Ostrinia nubilalis), a caterpillar that first feeds in the leaf whorl, then bores into stalks and ear shanks, weakening the plant from inside. Organic treatment Check the young leaf whorls and rub out the egg patches and small caterpillars before they tunnel in. An organic Bt spray only works while they are still out on the leaves; once inside the stalk you cannot reach them.Scout the whorls and pick off egg masses and young larvae before they bore in; a Bt product reaches them only while they are still feeding in the open whorl. Once inside the stalk they are protected. Prevention Chop up and dig in the old cornstalks after harvest, because the borer spends the winter inside them, and move your corn to a new spot each year.Shred and turn under cornstalks after harvest, since the borer overwinters in old stalks; rotating away from last year's patch helps too.

The control ladder

The ladder troubleshoots from the gentlest solution to the strongest. Start with the gentlest option and only move on when and if it doesn't work.

Off-season tillage

After harvest, chop the old cornstalks up and dig them into the bed. The caterpillars spend the winter inside those stalks, so working the residue in cuts down how many come back.Shred and incorporate stalk residue post-harvest. The overwintering stage sits inside old stalks, so destroying the residue is the main between-season lever.
Crop rotation

Move the corn to a different part of the garden each year rather than replanting last year's patch.Rotating the planting away from last season's block backs up residue destruction; it is offered as a supporting step rather than a stand-alone one.
Handpicking

Scout the whorl, the tight cluster of new leaves at the center of each plant, on a routine. Rub out the egg patches and small caterpillars you find there before they get into the stalk.Whorl scouting with hand removal of egg masses and early instars covers the window that matters; after larvae enter the stalk or ear shank they are protected from anything applied to the outside.
Bacillus thuringiensis (Bt)

A Bt spray, a bacterial product the caterpillars have to eat, reaches the borers while they are still feeding out in the open whorl. Once they are inside the stalk it will not get to them.Bt covers the same open-whorl window as handpicking and suits widespread whorl feeding; it has no reach on larvae already tunneled into stalk tissue.

The bottom rungs are products with label rules: timing, pollinators, and days to wait before harvest. Before you spray →

Cutworms

P · 03

Symptoms Young corn plants cut off right at the ground overnight, as if with scissors. If you dig near a cut plant, you often find a fat gray caterpillar curled up in the soil.Young seedlings clipped off at or just above the soil line overnight, often toppled and left; a gray, greasy-looking caterpillar curls up just below the surface nearby. Cause Cutworms, fat caterpillars that live in the soil and come out at night to chew through young stems at the base.Cutworms, the soil-dwelling larvae of several night-flying moths, which sever tender seedling stems at the base as they feed after dark. Organic treatment Go out at night with a flashlight and pick them off, or dig around a freshly cut plant to find the culprit. A little collar of cardboard or foil pushed into the soil around each stem keeps them out.Handpick at night or just under the soil around fresh damage; a cardboard or foil collar pushed an inch into the soil around each seedling blocks them. Prevention Clear weeds from the bed before you plant, because the moths lay their eggs in weedy soil, and plant into warm soil so the seedlings grow quickly past the tender stage.Keep the bed weed-free before planting, since cutworm moths lay in weedy ground, and delay sowing until the soil is warm and seedlings grow fast through the vulnerable stage.

The control ladder

The ladder troubleshoots from the gentlest solution to the strongest. Start with the gentlest option and only move on when and if it doesn't work.

Stem collars

Set a cardboard or foil collar around each young stem, pushing it about an inch into the ground. Cutworms chew at the base, so the collar puts a wall between them and the plant.A cardboard or foil collar set an inch into the soil rings each seedling through establishment, the stage when stems are still soft enough to be severed at the base.
Handpicking

A flashlight after dark is the tool here: take the caterpillars off by hand, or scratch through the top inch of soil beside a plant that was cut overnight, where the culprit tends to lie curled up.Night collection plus digging just under the surface next to fresh damage works at low to moderate numbers; the larvae feed after dark and shelter shallowly by day.

No spray for this one. Prevention is the control.

Flea beetles

P · 04

Symptoms Tiny dark beetles that hop away when you get close, leaving the young leaves peppered with little pinholes. Bad early damage stunts small plants and can spread a corn disease.Tiny dark beetles that jump when disturbed, leaving fine pinholes and shot-hole pitting in the leaves of young plants; heavy early feeding stunts seedlings and can transmit Stewart's wilt. Cause Small beetles called flea beetles that chew young corn leaves. One kind also carries the germ that causes Stewart's wilt, a corn disease, spreading it as it feeds.Several flea beetle species that feed on corn seedlings; the corn flea beetle also carries the bacterium that causes Stewart's wilt from plant to plant. Organic treatment Small plants usually grow past light damage. If the beetles are thick, cover the young plants with a lightweight row cover, taking it off when the tassels form so the wind can pollinate, and use an organic spinosad spray only if you must.Seedlings usually outgrow light feeding; where beetles are thick, a floating row cover over young plants (removed at tasseling for pollination) protects them, and spinosad is labeled if needed. Prevention Pull weeds that shelter the beetles, plant into warm soil so the corn grows quickly, and pick varieties that resist Stewart's wilt if it is a problem where you live.Control weeds that harbor the beetles, plant after the soil warms so seedlings grow fast, and choose Stewart's-wilt-tolerant varieties where the disease occurs.

The control ladder

The ladder troubleshoots from the gentlest solution to the strongest. Start with the gentlest option and only move on when and if it doesn't work.

Resistant varieties

Where Stewart's wilt occurs in your area, pick a variety described as tolerant of it. That does not stop the beetles chewing the leaves; it limits the disease they can pass along while they feed.Varietal tolerance here is aimed at Stewart's wilt, the bacterial disease the corn flea beetle vectors, not at the feeding injury itself. It is a seed-buying decision, made where the disease occurs locally.
Floating row cover

Where beetles are thick on the seedlings, cover the young plants with lightweight row cover fabric. Take it off when the tassels form so the wind can carry pollen to the silks.Row cover over the seedling stage is the exclusion step under heavy pressure; it has to come off at tasseling because corn sets its ears by wind pollination.
Spinosad

Light feeding is usually something small plants grow past, so hold an organic spinosad spray back for the times seedlings are actually being set back.Spinosad is labeled if needed, but fine pitting on plants that are growing away from it does not call for a spray.

The bottom rungs are products with label rules: timing, pollinators, and days to wait before harvest. Before you spray →

Raccoons

P · 05

Symptoms Ears torn open and eaten, and stalks knocked over, appearing overnight right when the corn is ready. Raccoons seem to know the exact night before you plan to harvest.Ears pulled down, husked, and half-eaten overnight as the kernels fill, with stalks knocked flat; the damage can arrive fast once the ears are worth raiding. Cause Raccoons, which raid ripe corn at night and can clear a small patch in a night or two. They are one of the most common reasons a home corn crop is lost.Raccoons, which raid corn from the milk and dough stages on and can strip a patch in a night or two; they are one of the most common causes of a lost home crop. Organic treatment You cannot spray for raccoons; you have to keep them out. A short two-wire electric fence, switched on as the ears get close to ready, is the surest way to protect the patch.There is no spray; exclusion is the answer. A two-wire electric fence (about 4 and 8 inches high) turned on as ears near maturity is the most reliable home defense. Prevention Set up and turn on the fence before the corn is ripe, not after the first raid. Once raccoons find your corn, they come back every night.Put the fence up and energize it before the ears fill out, not after the first raid, since once raccoons find the patch they return nightly.

The control ladder

The ladder troubleshoots from the gentlest solution to the strongest. Start with the gentlest option and only move on when and if it doesn't work.

Exclusion fencing

You cannot spray for raccoons, so the job is keeping them out. Run a short two-wire electric fence around the patch, the wires low at roughly 4 and 8 inches off the ground, and switch it on as the ears get close to ready. Do it before the corn is ripe rather than after the first raid: once raccoons have found your corn they come back every night.Exclusion is the whole control here, since no spray applies. A two-wire electric fence at about 4 and 8 inches, energized before the ears reach the milk stage, is the most reliable home defense. Timing carries as much weight as the fence itself, because a barrier raised after the first raid is trying to break an established nightly route rather than prevent one.

No spray for this one. Prevention is the control.

Diseases

Common smut

D · 01

Symptoms Puffy silver-white growths on the ears or stalks that later burst into a cloud of black powder. On the ear, these galls take the place of kernels. They show up most on stressed or damaged plants.Silvery-white galls on ears, tassels, or stalks that swell, then rupture to release a mass of powdery black spores; ear galls replace kernels and are most common on stressed or injured plants. Cause A fungus that gets in through wounds and silks, especially in hot, dry spells, and forms the galls. Its spores can survive in the soil for years.The fungus Ustilago maydis, which enters through wounds and silks and is favored by hot, dry weather punctuated by injury; its spores survive years in the soil. Organic treatment There is no home spray. Cut off and throw away (do not compost) the galls before they burst, so their spores do not spread into your soil.There is no spray for the home garden; cut off and bag the galls before they rupture and blacken, to keep spores out of the soil. Do not compost them. Prevention Try not to injure the plants while weeding, keep water and feeding steady so the corn is not stressed, move your corn each year, and pick more resistant varieties if smut keeps coming back.Avoid wounding plants during cultivation, keep moisture and fertility steady to reduce stress, rotate away from infected beds, and choose more tolerant varieties where smut recurs.

The control ladder

The ladder troubleshoots from the gentlest solution to the strongest. Start with the gentlest option and only move on when and if it doesn't work.

Resistant varieties

If smut turns up year after year, look for a variety described as more tolerant of it when you buy seed.Varietal tolerance is the seed-buying lever where smut recurs in the same ground. It is tolerance rather than immunity, so keep the removal step running alongside it.
Crop rotation

Move the corn to a different bed each year. The fungus can sit in the soil for years, so replanting the same spot keeps handing it another crop.Spores persist in soil for years, so rotating out of an infected bed is the standing cultural step; it lowers what is waiting there rather than clearing it.
Garden sanitation

Cut off the galls, the puffy silver-white growths, and bag them for the trash before they burst open. Keep them out of the compost, since the black powder inside is spores headed for your soil.Excise and bag galls while they are still silvery and intact; once one ruptures the teliospores are already loose. Trash rather than compost.

No spray for this one. Prevention is the control.

Common rust

D · 02

Symptoms Small rusty-brown, powdery spots on both sides of the leaves that darken later in the season. A bad case yellows the leaves and can leave the ears less full.Small cinnamon-brown, powdery pustules scattered on both leaf surfaces, darkening toward the season's end; heavy infection yellows and kills leaf tissue and can cut ear fill. Cause A fungus whose spores blow in on the wind and take hold in cool, damp weather. In most gardens it arrives fresh each year rather than surviving the winter in place.The fungus Puccinia sorghi, whose spores blow in on the wind and infect under cool, moist, humid conditions; it does not overwinter in most northern gardens but arrives each year on wind currents. Organic treatment Most gardens can live with a little rust. Pull off the worst lower leaves to slow it and give the plants air. You rarely need to spray in a home garden.Most home crops tolerate rust without treatment; remove badly infected lower leaves to slow spread and improve airflow. A labeled fungicide is rarely needed in a garden. Prevention Pick rust-resistant varieties, which are easy to find, and plant early so the corn is nearly done before rust gets bad late in summer. Water at the base when you can.Choose rust-resistant hybrids, which are widely available, and plant early so the crop matures before rust builds late in the season; avoid overhead watering where practical.

The control ladder

The ladder troubleshoots from the gentlest solution to the strongest. Start with the gentlest option and only move on when and if it doesn't work.

Resistant varieties

Rust-resistant varieties are easy to find, so start there when you buy seed.Resistant hybrids are widely available and carry most of the load. The pathogen blows in on wind currents rather than overwintering in most northern gardens, so there is little local carryover to manage.
Disease-escape sowing

Plant early in your window so the corn is nearly done before rust gets bad late in summer, which is this crop's guidance alongside the rust-resistant variety this ladder starts with. The one limit is the soil itself, since corn seed rots in cold, wet ground; this method's cautions carry the soil temperatures to wait for.An early planting takes the crop through silking and grain fill before rust builds late in the season, which is this crop's guidance and why the rung sits beside the resistant hybrid at the front of the ladder: both are settled before anything is in the ground. The floor is the seedbed, because corn seed sown into cold, wet soil rots rather than emerges, and this method's cautions carry the temperatures that set it.
Water at the base

Water at the soil line instead of over the top of the plants where you can. Rust takes hold in cool, damp conditions, so leaving less water sitting on the leaves helps.Skip overhead irrigation where practical. Infection favors cool, moist, humid weather, and base watering keeps leaf wetness periods shorter.
Garden sanitation

Take the worst of the lower leaves off to slow the spread and let more air through the plant. Most home patches live with some rust and no spray at all.Removing the most heavily pustuled lower leaves slows spread and opens the canopy; a labeled fungicide is rarely warranted at garden scale, where tolerating the infection is the usual outcome.

No spray for this one. Prevention is the control.

Stewart's wilt

D · 03

Symptoms Long yellow streaks with wavy edges running down the leaves, appearing after flea beetles have been feeding. A bad early case wilts and stunts young plants and can kill them.Long, pale-green to yellow streaks with wavy margins running along the leaves, following flea-beetle feeding scars; severe early infection wilts and stunts seedlings, sometimes killing them. Cause A bacterium spread by the corn flea beetle as it feeds. After a mild winter more beetles survive, so the disease tends to be worse the next year.The bacterium Pantoea stewartii, carried and introduced by the corn flea beetle; mild winters that let more beetles survive drive worse outbreaks the following year. Organic treatment You cannot cure an infected plant; pull and throw away badly affected seedlings. The real control is keeping the flea beetles that spread it in check.There is no cure once a plant is infected; remove and destroy severely affected seedlings. Management is aimed at the flea-beetle vector, not the bacterium itself. Prevention Grow resistant varieties, which is the main defense, and keep flea beetles off young plants with a row cover or an organic treatment so they cannot pass the disease along.Grow resistant or tolerant hybrids, the primary defense, and manage flea beetles on young plants with row cover or a labeled treatment to break the transmission cycle.

The control ladder

The ladder troubleshoots from the gentlest solution to the strongest. Start with the gentlest option and only move on when and if it doesn't work.

Resistant varieties

Resistant or tolerant varieties are the main defense here, so choose them at seed-buying time if this disease shows up where you garden.Hybrid resistance is the primary control. Nothing is curative once the bacterium is in the plant, so the decision is made at seed purchase.
Garden sanitation

There is no cure for a plant that is already infected. Pull badly affected seedlings and get rid of them rather than waiting to see whether they come back.Rogue and destroy severely affected seedlings. Infected plants do not recover, and management shifts to the vector rather than the bacterium.
Floating row cover

Covering young plants with row cover keeps corn flea beetles, the insects that carry this bacterium from plant to plant, off the seedlings during the stage when infection does the most harm. Take the cover off at tasseling so the corn can pollinate.Row cover over seedlings breaks the transmission cycle by excluding the corn flea beetle vector through the most damaging infection window; it comes off at tasseling for wind pollination.

No spray for this one. Prevention is the control.

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Seasoned

Where to plant next year

Crop rotation

Move your corn to a new spot each year, on about a two-to-three-year cycle. Planting it where beans or peas grew the year before gives it the extra nitrogen it wants.Rotate corn on a two-to-three-year cycle and place it after a nitrogen-fixing legume where you can, since corn is a heavy nitrogen feeder.

Family

Poaceae (grass)

Years between

2 years

in the same bed

Avoid following

Try not to plant corn in the same spot two years running. Moving it each year keeps corn diseases and pests from building up and gives the soil a rest from its heavy feeding.Avoid following corn with corn in the same bed; rotating breaks the buildup of soil-borne diseases and corn pests, and spreads out the crop's heavy nitrogen demand.

Plant after

Corn follows a legume well: beans or peas leave nitrogen in the soil that this hungry crop puts straight to use.

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