Acorn Squash in Zone 5 -- plant

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

Plant acorn squash in rich, well-drained soil with plenty of compost mixed in. It is a large, long-season plant, so give it a generous, fertile bed. Many gardeners plant on low hills or mounds, which warm up faster and drain better. If your soil is heavy or stays wet, build up mounds or use raised beds so the roots and developing fruit do not sit in water.

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 · 6-10 hrs/day

Water

moderate

Spacing

24-48 inches

Soil

loam

Days to maturity

80-100 days from transplant

Soil pH

6 to 6.8

Container OK?

Yes · 10+ gal pot

Germination temp

70-95°F

Soil chemistry

Soil pH for acorn squash

Preferred

6 to 6.8

Tolerated

5.8 to 7.5

Acorn squash likes soil that is slightly acidic to neutral, about pH 6.0 to 6.8, and most garden soil is already close. An inexpensive soil test tells you where you stand and whether you need to adjust it before planting.Acorn squash does best in slightly acidic to neutral soil, around pH 6.0 to 6.8, with a sweet spot near 6.0 to 6.5. It still grows across a wider band, roughly 5.8 to 7.5, but uptake of some nutrients tightens as the soil turns alkaline. Test before planting and lime or add sulfur only on the test's advice rather than by guess.

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Steady hand on the hose

Watering

When & how much

Frequency

Give acorn squash about 1 to 1.5 inches of water a week, more when it is hot and dry. Water deeply rather than a little every day.Aim for at least 1 inch of water per week, leaning to 1.5 inches in heat or sandy soil, delivered deeply and less often rather than in light daily sprinkles. The long-season, big-leaved vine transpires heavily through summer.

Amount

About 1 to 1.5 inches of water a week is a good target, more while the plant is flowering and the squash are growing.Around 1 to 1.5 inches per week is the working range, leaning higher during flowering and fruit sizing and through hot, dry spells. Even, deep watering builds well-formed fruit; let it swing dry and you get poor set and small, uneven squash.

Method

Water the soil, not the leaves, using a soaker hose or watering wand at the base. Keeping the leaves dry helps prevent mildew. As the squash ripen and the skin hardens, ease off the water.Water at the base of the plant with drip or a soaker hose, keeping the foliage as dry as possible, since wet leaves invite powdery and downy mildew. Taper watering as the fruit nears maturity and the rind hardens, which firms the rind for storage, and keep ripening fruit off saturated soil.

Signs of trouble

Too much water

If lower leaves yellow, the plant wilts even though the soil is wet, or fruit and stems go soft and rotten, it is getting too much water or the soil drains poorly.Yellowing lower leaves, wilting even when the soil is wet, and soft, rotting stems or fruit at the base point to overwatering or poor drainage. Saturated soil invites crown and fruit rot, especially on heavy ground.

Too little water

Some midday wilting in hot weather is normal and passes by evening. Leaves that stay wilted mean the plant is too dry, and drought while fruit is forming gives small, poorly filled squash.Midday wilting that recovers overnight is normal in heat, but leaves that stay limp and dull signal real drought. Dry spells during fruit sizing show up as small, poorly filled squash and aborted young fruit.

Feeding rhythm

Feeding

Frequency

At planting, then side-dress once or twice

Type

balanced at planting, then nitrogen side-dress

When to start

Work into the bed before planting, then side-dress about 3 to 4 weeks after planting and again at flowering

Acorn squash grows for a long time and likes steady feeding. Mix a balanced fertilizer into the soil before planting, then feed with a little extra nitrogen about three to four weeks later as the vines start to run, and again when flowers appear. Once the squash begin to form, go easy on the nitrogen, because too much makes leafy vines instead of fruit.Acorn squash is a moderate feeder over a long season. Work a complete fertilizer such as 10-10-10 into the bed before planting, then side-dress with nitrogen about three to four weeks after planting as the vines begin to run, and again as flowering starts. Ease off heavy nitrogen once fruit has set, since late, lush vine growth comes at the expense of fruit and draws pests. Pair feeding with even moisture, because the nutrients only help a plant that is not also drought-stressed.

N · P · K = 10-10-10

Use a balanced fertilizer like 10-10-10 at planting, then a little nitrogen as the vines spread. Do not overdo the nitrogen once fruit forms.A complete fertilizer such as 10-10-10 worked in at planting, then a nitrogen side-dress while vines run, easing off once fruit sets. Avoid pushing high nitrogen late, which gives vine at the expense of fruit.

Try balanced 10-10-10 at planting, then a nitrogen source such as blood meal or 46-0-0

Who grows well together

Companion planting

The most useful acorn squash companions are flowers that bring in bees, since acorn squash needs lots of bee visits to set fruit, and the traditional Three Sisters partners, corn and beans. Nasturtiums can lure pests away. The one rule that really matters is to keep acorn squash away from other squash, cucumbers, and melons, which all share the same pests and diseases. Most acorn squash companion pairings are traditional rather than trial-tested, and the ones worth acting on serve two practical ends: pollination and pest pressure. Because cucurbit fruit set is pollinator-limited, with each female flower needing many bee visits, flowering insectary plants like borage near the patch are a genuine help. The Three Sisters partners, corn and beans, give the sprawling vines structure and a nitrogen boost while sharing none of acorn squash's pests, and a trap planting of nasturtium can divert squash bugs and beetles. The firmest rule is a rotation one: keep acorn squash away from other cucurbits, which share the full squash pest and disease complex, including the squash vine borer this pepo squash is prone to.

Other

Corn

Corn and acorn squash are the traditional Three Sisters pairing. The corn stands tall while the squash vines spread along the ground, and the big leaves shade out weeds. It is a time-tested combination more than a proven boost.The classic Three Sisters partner: tall corn gives sprawling acorn squash vines structure and light shade in high heat, while the broad squash leaves shade the soil and suppress weeds beneath the corn. A long-standing intercropping tradition with a sound space-and-shade rationale, not a measured yield effect for this exact pair. Traditional

Beans

Beans are the third Three Sisters plant. They pull nitrogen from the air into the soil, which the hungry squash appreciates, and they do not share acorn squash's pests. A good, traditional neighbor.The third of the Three Sisters: pole or bush beans fix nitrogen that benefits the long-feeding acorn squash, and they share none of the cucurbit pests. A traditional, mechanistically plausible pairing rather than a trial-isolated one. Well-grounded

Nasturtium

Nasturtiums are often grown near squash to lure squash bugs and beetles away, and their flowers bring in bees, which acorn squash needs to set fruit. A helpful, low-risk neighbor.Often planted near cucurbits as a trap and deterrent for squash bugs and cucumber beetles, and its flowers also draw the bees acorn squash depends on for fruit set. Trap cropping is a documented principle, but the specific nasturtium-acorn squash effect is not formally isolated, so treat it as a plausible aid. Well-grounded

Borage

Borage flowers are loved by bees, and acorn squash needs lots of bee visits to set fruit, so a few borage plants nearby can help with pollination. Mainly grown to bring in bees.A strong bee magnet whose flowers recruit the pollinators that acorn squash fruit set depends on, since each female flower needs many bee visits to size a fruit. Pollinator-habitat value is well grounded; the specific borage-acorn squash pairing is traditional rather than trial-tested. Well-grounded

Keep apart from

Other cucurbits Keep acorn squash away from other squash, cucumbers, and melons. They share most of the same pests and diseases, including the squash vine borer, so planting them together makes those problems worse.Cucumber, melon, summer squash, and other winter squash share acorn squash's pest and disease complex, including squash bug, the squash vine borer that readily attacks this pepo squash, cucumber beetle with the bacterial wilt it spreads, and powdery and downy mildew. Grouping them concentrates that pressure and lets soilborne problems build. A real epidemiology and rotation principle rather than a tested adjacency effect: spread cucurbits out and rotate them. Well-grounded

Potatoes Some gardeners keep potatoes and squash apart, since both are big, hungry plants and potatoes can bring their own diseases. This is more tradition than a proven rule.A traditional caution that potatoes and cucurbits compete heavily and that potatoes can harbor disease and attract pests near squash. There is no strong T1 mechanism for the specific pairing, so it persists mostly as garden lore. Traditional

Provenance tagged inline · see methodology for the labeling system Key

Harvest signals

When to pick

Unlike summer squash, you pick acorn squash once, when it is fully ripe. The best sign is the pale spot where the squash sits on the ground: when it turns from cream or yellow to deep orange, the squash is ready. The rind should also be hard enough that you cannot dent it with a thumbnail, and the stem should be dry and woody. Do not just go by the green color, since acorn squash turns dark green long before it is ripe. Cut the squash off the vine with a knife, leaving a short piece of stem. Bring them in before a hard frost. You can eat acorn squash right away, and you should not cure it the way you would a butternut, since curing actually makes it worse.Harvest acorn squash once at full maturity, not young. The reliable ripeness sign is the ground spot, the patch where the fruit rests on the soil, which turns from cream or yellow to a deep orange; the rind should also be hard enough that a thumbnail cannot dent it, dull rather than glossy, and the stem dried and corky. Do not go by the dark green rind alone, since acorn squash colors up weeks before it is ripe. Cut the fruit from the vine with shears or a knife, leaving a 1 to 2 inch handle of stem, and avoid carrying it by the stem. Get the crop in before a hard frost, which damages the rind and shortens storage. Acorn squash is good to eat straight from the vine and, unlike a butternut, should not be cured: the heat and humidity of curing reduce its quality and shorten its already brief storage.

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Yield

What to expect

An acorn squash plant usually gives you several small squash, often 4 to 6, each about 1 to 2 pounds. Bush types like Table King make fewer but take much less room. A plant or two goes a long way.A healthy acorn squash vine typically yields 4 to 6 small fruit of about 1 to 2 pounds each; compact and bush types set a few fruit on far less space. Vining types need room per plant, and even moisture and feeding through sizing build full, sweet, well-formed squash.

Unlike summer squash, acorn squash does not keep producing all season. The plant sets its fruit over the summer and they all ripen together in fall, when you harvest once. Removing the latest tiny fruit helps the rest grow bigger before frost.Acorn squash does not produce continuously; the plant sets fruit through summer and then the crop matures together in fall for a single harvest. Once several fruit have set, removing the latest small fruit and pinching vine tips channels energy into sizing and ripening the keepers before frost. The big first-year surprise is that acorn squash turns dark green early, well before it is ripe, so do not go by color alone. Wait for the pale spot on the bottom to turn orange. Give vining types plenty of room, and grow flowers nearby for the bees.The usual first-year surprises are how pollinator-dependent fruit set is and that the dark green color arrives long before ripeness, so the real ripeness tell is the ground spot turning orange, not the rind color. Vining types also need more room than expected, though bush types stay tidy.

What changes yield

Pollination: fruit set is pollinator-limited, with each female flower needing many bee visits; poor pollination in cool or pollinator-scarce conditions drops young fruit.Season length: acorn squash needs a warm season of 80 to 100 days to mature before frost; a short season limits variety choice and yield.Space and habit: vining types sprawl 4 to 8 feet and need room, while true bush types stay compact; crowding cuts yield and worsens disease.Pest and disease pressure: squash bug, the squash vine borer that readily attacks this pepo squash, beetle-vectored bacterial wilt, and powdery and downy mildew can all end a planting early.Even moisture and feeding: steady water and moderate feeding through fruit sizing build full, well-formed squash.

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Pick your variety

Recommended varieties

Pick an acorn squash variety by your space. For a full-size, reliable squash on a vine, grow Table Queen. If your garden is small or you want to grow in a pot, choose a bush type like Table King or Honey Bear, and Honey Bear also stands up to mildew. Table Ace ripens early with sweet, low-fiber flesh, and Celebration has pretty striped fruit you can eat or use for fall decoration.Choose by habit and space. Where there is room, the open-pollinated Table Queen is the dependable full-size vining standard. For small beds or containers, the bush Table King and Honey Bear stay compact, and Honey Bear also resists powdery mildew. The semi-bush Table Ace matures earliest and carries low-fiber, sweet flesh, and Celebration adds multicolored fruit that doubles as fall decoration.

Table Queen

The classic open-pollinated acorn squash and the standard by which the rest are judged. Deeply ribbed, dark green, heart-shaped fruit about 1 to 2 pounds with sweet, fine-grained pale-orange flesh, on a full-size vining plant. The dependable, seed-saveable choice.

Table Ace

A hybrid semi-bush type with uniform, near-black, low-fiber fruit and sweet flesh, maturing early on a space-saving plant. A reliable, productive pick for shorter seasons and smaller gardens.

Table King

A compact bush acorn squash (an All-America Selections winner) that holds its dark green color well, making it a good fit for small beds and large containers where a full vining type will not fit.

Honey Bear

An All-America Selections winner with a compact bush habit and small, single-serving dark green fruit about 1 pound, bred with tolerance to powdery mildew. An excellent choice for small gardens, containers, and one-squash meals.

Celebration

A striking F1 with multicolored orange, cream, and green striped fruit on a semi-vining plant, good both for eating and for fall display. Sweet flesh in the tidy acorn shape.

Off the vine

Storing your harvest

Room temp

An acorn squash keeps at room temperature for about a month or two in a cool spot out of the sun, longer than summer squash but much less than a butternut. Keep it off cold, damp floors so the bottom does not rot.A sound acorn squash keeps at room temperature, the opposite of tender summer squash, but only briefly by winter-squash standards: figure about a month, up to two, in a cool room out of direct sun, not the half-year a butternut manages. It is the shortest keeper of the common winter squashes. Warm indoor heat shortens that further. It keeps best sitting on a shelf with airflow rather than on a cold or damp floor.

Fridge

Do not put a whole acorn squash in the fridge, it is too cold and makes it break down faster. Once it is cut, wrap the pieces and keep them in the fridge for a few days, or freeze them.Whole acorn squash is not refrigerated; cold storage below about 50°F causes chilling injury and faster breakdown. Cut squash and cooked or pureed flesh, however, should be refrigerated and used within a few days, or frozen.

Freezer

Acorn squash freezes well once cooked. Halve and roast or steam it, scoop the flesh out of the skin, cool it, and freeze it in portions. It keeps about a year.Acorn squash freezes well as cooked flesh: halve and roast or steam it, scoop the flesh from the rind, mash it or leave it in chunks, cool, and freeze in measured portions. Frozen cooked acorn squash keeps about a year.

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When something goes wrong

Common problems

Tiny squash turned yellow and rottedSmall fruit yellowed and rotted at the blossom end

01 of 04

What happened The flower was not pollinated well, so the little squash died instead of growing. This often happens in cool or rainy weather, or when there are few bees.Poor pollination. The female flower was not adequately pollinated, so the young fruit aborts, yellowing and rotting at the blossom end instead of sizing up. Common in cool, wet, or pollinator-scarce conditions, and acorn squash is strongly pollinator-dependent. Next season Grow some flowers nearby for the bees, and hand-pollinate early flowers if needed. It usually gets better as more flowers open.Plant flowers to draw bees, avoid spraying open blooms, and hand-pollinate in the morning if set is poor. It usually improves as more flowers open and bees get active.

Squash rotted on its undersideSquash sat on wet soil and rotted on the bottom

02 of 04

What happened The squash sat on wet ground and rotted on the bottom. Damp soil and poor drainage let a soil disease soften the fruit where it touched the ground.Fruit rot, typically from a wet underside in contact with damp soil, often a soilborne rot in poorly drained, rainy conditions. A soft, sometimes molded patch develops where the fruit sits, and can spread in storage. Next season Plant on raised hills so water drains away, and slip a board or straw under each squash so it is not on wet ground. Pick them and store them; there is no need to cure acorn squash.Plant on raised hills for drainage, avoid low wet spots, and set each sizing fruit on a board or thick mulch to lift it off the soil. Harvest promptly and store; there is no cure step for acorn squash.

Leaves got white and powdery and the plant died backLeaves turned white and powdery, then the plant faded early

03 of 04

What happened Powdery mildew, a white coating on the leaves, spread until the leaves died and the plant stopped early, so the squash did not finish well.Powdery mildew defoliated the plant ahead of schedule. The white fungal coating spread across the leaves until they browned and died, cutting the season short and reducing fruit size, fill, and sweetness. Next season Pick mildew-tolerant varieties, give plants more room and full sun, water the soil not the leaves, and treat the first white spots early.Choose mildew-tolerant varieties such as Honey Bear, space plants generously, plant in full sun, water at the base, and treat at the first spots from midsummer rather than waiting.

Acorn squash was dry and stringy, not sweetCut an acorn squash that was dry, stringy, and fibrous instead of sweet and moist

04 of 04

What happened The squash was either picked too early, so it was watery, or it was kept too long or cured. Acorn squash goes stringy and dry if it is cured or stored too long, and a squash that has turned all orange is past its best.Either the squash was picked before full maturity, so its flesh was thin, pale, and watery, or, more often, it was left too long or held too warm. Acorn squash that has turned mostly orange all over is past its prime, and, unlike other winter squash, it should not be cured: a warm, humid cure, or simply storing it too long, dries the flesh out and makes it coarse and stringy. The best-eating acorn squash is one harvested at maturity, a hard rind with just the ground spot turned orange, and eaten within a month or two. Next season Pick when the skin is hard and the bottom spot has just turned orange, not when the whole squash is orange. Do not cure it, keep it somewhere cool, and eat it within a month or two.Harvest at maturity, a hard, dull rind and a ground spot just turned orange, not a fruit that has gone orange all over. Skip curing entirely, store cool at 50 to 55°F, and eat within a month or two while the flesh is still sweet and moist.

The usual suspects

Pests & diseases

Pests

Squash bug

P · 01

Symptoms Leaves get yellow spots, then brown and wilt, and you find clusters of shield-shaped gray-brown bugs and their bronze eggs on the undersides of leaves near the base of the plant.Leaves develop yellow specks that brown and wilt, and heavily fed vines wilt rapidly and turn brittle, a damage pattern sometimes called anasa wilt. Flat bronze egg clusters appear on leaf undersides along the veins, and gray-brown adults and pale nymphs cluster near the crown and under debris. Cause Squash bugs pierce the leaves and stems and suck out the juices, which makes the vines wilt. They breed through the summer and hide in plant debris over winter.The squash bug, a true bug that feeds with piercing-sucking mouthparts on cucurbit foliage and stems, injecting saliva that wilts and browns the vines. Populations build through the season and are hardest to control once nymphs are large; the bugs overwinter as adults in garden debris. Organic treatment Pick the bugs off by hand and scrape off the egg clusters under the leaves. A board laid on the ground overnight draws them underneath, then lift it in the morning and destroy them. Treat the young bugs with insecticidal soap.Hand-pick adults, crush the egg masses on leaf undersides, and trap bugs by laying a board near the plants overnight, then lifting it in the morning and destroying the cluster underneath. Target young nymphs with insecticidal soap, since large nymphs and adults are tough to kill. Prevention Cover young plants until they flower, check under the leaves for eggs early in the season, and clean up old vines after harvest so the bugs have nowhere to overwinter.Use row cover on young plants until flowering, clean up vines and debris at season's end to cut overwintering sites, and rotate cucurbits. Scout leaf undersides for the bronze egg clusters from early in the season and act before nymphs mature.

Cucumber beetles

P · 02

Symptoms Small yellow beetles with stripes or spots chew on the leaves and flowers, especially of young plants. Worse, they can spread a disease called bacterial wilt that makes the vines collapse later.Small yellow beetles, striped or spotted, chew young leaves, stems, and flowers, and can scar developing fruit. The bigger threat is indirect: striped and spotted cucumber beetles transmit bacterial wilt, so beetle feeding on seedlings can be followed weeks later by sudden vine wilt. Cause Cucumber beetles feed on acorn squash plants and carry the germ that causes bacterial wilt, infecting the plant as they chew. Young seedlings are most at risk.Striped and spotted cucumber beetles feed on cucurbits and carry the bacterium that causes bacterial wilt in their gut, infecting plants as they feed. Seedlings are most vulnerable; once plants have several leaves they tolerate some feeding, and bacterial wilt is generally less severe in winter squash like acorn squash than in cucumber and melon. Organic treatment Cover young plants with row cover (remove it when flowers open), pick the beetles off, and use yellow sticky traps. Keeping the beetles down is the best way to avoid the wilt disease they spread.Protect seedlings with row cover removed at flowering, hand-pick beetles, and use yellow sticky traps to monitor and reduce numbers. Where bacterial wilt is a known problem, controlling the beetles is the most effective control of the disease, since there is no cure once a plant is infected. Prevention Cover seedlings until they flower, keep them growing strong, clear away weeds and old plants, and do not plant where squash-family crops grew last year.Exclude beetles from seedlings with row cover, keep young plants vigorous so they grow past the vulnerable stage, clear weeds and debris, and rotate away from where cucurbits grew. Aim control at the early-season colonizers that vector wilt.

Squash vine borer

P · 03

Symptoms A healthy plant wilts all at once in summer, with what looks like wet sawdust at a hole near the base of the stem and a fat white grub inside. Acorn squash is one of the squashes borers love, so watch for this.A vigorous vine wilts suddenly in mid to late summer, often one runner at a time, with sawdust-like frass oozing from a small hole low on the stem and a fat white caterpillar tunneling inside. As a Cucurbita pepo, acorn squash is a preferred, susceptible host, so a healthy plant can collapse within days once a borer is inside. Cause A moth lays eggs at the base of the stem in early summer, and the grubs tunnel inside and kill the vine. The moth likes thin-stemmed squash such as acorn squash and zucchini, so this squash is a common target.The larva of the squash vine borer moth, which lays eggs at the stem base in early summer; the hatching larvae bore into the stem and cut off the plant's water. The moth strongly prefers thin-stemmed Cucurbita pepo squash, which includes acorn squash along with zucchini, spaghetti squash, and summer squash, so this is a pest to plan for rather than hope to avoid. Organic treatment Check the base of the stems often in summer. If you find a borer, slit the stem with a knife, dig out the grub, and cover the spot with damp soil so the vine can re-root. Pull and destroy badly damaged vines so the pest does not come back next year.Catch it early: scout the stem base for frass from early summer. If a borer has entered, slit the stem lengthwise with a knife, remove the larva, and mound moist soil over that node to encourage re-rooting. Burying vine joints as they run so a damaged plant can survive on secondary roots, and removing and destroying infested vines at season's end, both reduce next year's brood. Prevention Cover young plants with a light row cover until they flower, then take it off so bees can reach the blooms. Check the base of the stems for the sawdust-like frass starting in early summer, and clean up old vines after harvest so borers cannot overwinter.Row cover from planting until flowering excludes the egg-laying moths and is the most reliable defense; remove it at bloom so bees can pollinate. Time a planting to dodge the main moth flight where its timing is known, wrap or mound soil over the lower stem, and choose bush or semi-bush types, which some growers find recover better. Scout the stem base for frass from early summer and act at the first sign.

Aphids

P · 04

Symptoms Tiny soft insects gather on the undersides of leaves and on new growth, making leaves curl and turn yellow, often with a sticky film. They can also spread viruses.Colonies of small soft-bodied insects, often melon aphids, cluster on leaf undersides and growing tips, causing leaves to curl, pucker, and yellow, with sticky honeydew and sooty mold following. Beyond direct feeding, aphids transmit mosaic viruses that mottle and distort the foliage. Cause Aphids are small insects that suck the plant's juices and multiply fast, especially on soft, over-fed growth. The sticky honeydew they leave behind grows black mold.Melon and other aphids suck sap and reproduce rapidly in warm weather, building up quickly on stressed or over-fertilized plants. The honeydew they excrete fosters sooty mold, and several aphid species spread cucurbit mosaic viruses. Organic treatment Blast them off with a strong spray of water and treat the undersides of the leaves with insecticidal soap, repeating every few days. Ladybugs and other helpful insects eat aphids, so welcome them.Knock colonies off with a strong jet of water and spray insecticidal soap or horticultural oil with thorough coverage of leaf undersides, repeating every few days. Conserve ladybugs, lacewings, and parasitic wasps, which usually bring aphids under control. Prevention Do not over-fertilize with nitrogen, check the undersides of leaves regularly, and let helpful insects do their work instead of spraying everything.Avoid excess nitrogen, which drives the soft growth aphids favor, scout leaf undersides and growing tips, and support natural enemies rather than spraying broadly. Reflective mulch deters aphids from young plants.

Diseases

Powdery mildew

D · 01

Symptoms A white, powdery coating spreads over the leaves until they turn yellow and brown and die. The plant fades early, and the squash may not size up or sweeten well.White, powdery patches appear first on the upper and lower leaf surfaces and stems, spreading until leaves yellow, brown, and die back ahead of schedule. Early defoliation cuts the season short, reduces fruit size and the sugars that make acorn squash sweet, and exposes fruit to sunscald. Cause A fungus that spreads on warm, humid days, especially where plants are crowded and air does not move well. It does not need wet leaves to take hold.Powdery mildew fungi that thrive in warm conditions with high humidity but do not need leaf wetness, spreading by wind-blown spores. Crowded plantings, poor airflow, and shade worsen it, and it is one of the most common late-season winter-squash diseases. Organic treatment Treat early, at the first white spots, with a labeled fungicide like sulfur or horticultural oil, and remove badly affected leaves. Water the soil, not the leaves. Once it covers the plant it is hard to stop.Treat at the first spots, before it spreads, with a labeled fungicide such as sulfur or a horticultural oil or biofungicide, covering both leaf surfaces, and remove the worst leaves. Avoid overhead watering. Once it is widespread, control is mostly damage limitation. Prevention Pick mildew-tolerant varieties if you can, give plants plenty of room so air moves between them, plant in full sun, and water at the base. Start checking in midsummer and act at the first white spots.Choose mildew-tolerant varieties where available (some acorn squash types such as Honey Bear hold up better), space plants generously for airflow, plant in full sun, and avoid excess nitrogen and overhead watering. Scout from midsummer and treat at the first sign, since prevention and early action beat rescue.

Downy mildew

D · 02

Symptoms Yellow patches show on top of the leaves with fuzzy gray growth underneath, mostly in damp, humid weather. The spots brown and spread until the leaves die.Angular yellow blotches, bounded by the leaf veins, appear on the upper leaf surface, with a grayish or purplish fuzzy growth on the underside in humid weather. Spots brown and coalesce, and severe infection rapidly defoliates the vines. Cause A mold-like disease that spreads in wet, humid weather and needs wet leaves to infect. It can move through a planting quickly.A fungus-like water mold that spreads on wind-borne spores and needs leaf wetness and humidity to infect, so it flares in wet, humid spells and dewy conditions. It moves fast once established and is favored by crowding and prolonged leaf wetness. Organic treatment Open up the planting so leaves dry faster, remove the worst leaves, and use a labeled fungicide when wet weather sets in. Do not water over the leaves.Improve airflow, let foliage dry, remove badly affected leaves, and apply a labeled fungicide, covering leaf undersides, when conditions favor the disease. Avoid overhead irrigation, which keeps leaves wet and feeds the infection. Prevention Give plants room so air moves between them, water at the base, and watch closely in humid weather. Choose resistant varieties if downy mildew is common where you live.Space for airflow, water at the soil line rather than overhead, choose resistant varieties where available, and avoid working among wet vines. Scout closely in humid weather, when the disease can appear and spread quickly.

Bacterial wilt

D · 03

Symptoms Vines wilt and die even though the soil is wet. If you cut a wilted stem and pull the two ends apart slowly, infected sap stretches into sticky white strings.Individual leaves, then whole vines, wilt and collapse even though the soil is moist, often spreading until the plant dies. A field test helps confirm it: cut a wilted stem and slowly draw the cut ends apart, and infected sap pulls into thin, sticky white strands. Cause A germ spread by cucumber beetles as they feed. It blocks the plant's water pipes, so the vine wilts even when watered. Acorn squash is somewhat less prone than cucumbers or melons.A bacterium spread by striped and spotted cucumber beetles, which carry it in their gut and infect plants as they feed. It clogs the water-conducting tissue, so the plant wilts despite adequate water. Winter squash like acorn squash are generally less susceptible than cucumber and melon, but losses still occur. Organic treatment There is no cure once a plant has it, so pull and destroy infected plants. The real fix is keeping cucumber beetles down, since they spread it.There is no cure once a plant is infected; remove and destroy wilting plants to limit spread. Control is really beetle control, so management aims at keeping cucumber beetle numbers down, especially early in the season. Prevention Keep cucumber beetles under control, since they spread the disease. Cover young plants until they flower, and pull any plant that wilts and tests positive.Manage cucumber beetles from seedling stage with row cover removed at flowering, keep young plants vigorous, and remove infected plants promptly. Controlling the beetle vector is the most effective control of the disease.

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Seasoned

Where to plant next year

Crop rotation

Try not to grow acorn squash or its relatives in the same spot more than once every 3 years or so. Moving them around the garden each year helps avoid a buildup of pests and disease. Clean up old vines at the end of the season too.Rotate cucurbits on a 3 year cycle, returning acorn squash to a given bed no sooner than the third or fourth year, to break the buildup of squash bug, beetle-vectored wilt, and soilborne disease. Clear and remove spent vines at season's end rather than tilling them in, which removes overwintering pest and disease sites and makes rotation more effective.

Family

Cucurbitaceae

Years between

3 years

in the same bed

Avoid following

Do not plant acorn squash where you grew cucumbers, melons, or other squash in the last few years. They get the same pests and diseases, which build up in the soil.Avoid planting acorn squash where another cucurbit grew in the last few years, including cucumber, melon, summer squash, and other winter squash. They share squash bug, cucumber beetle, bacterial wilt, the mildews, and soilborne rots, all of which build up in the soil and on debris.

Plant after

Legumes such as beans and peas, sweet corn, leafy greens, or alliums like onions and garlic make good preceding crops, since they do not share the cucurbit pest and disease complex, and a legume leaves nitrogen behind for the long-feeding acorn squash.

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Acorn Squash

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