Butternut Squash Growing
Updated: Sep 15, 2022
A vine-growing winter squash, butternut has a sweet and nutty taste that’s similar to pumpkin. It makes tasty soups and is delicious when roasted. Butternut squash is also packed with vitamins, minerals, nutrients, and antioxidants.
To help ensure your Butternut Squash thrives, I’ve put together this how-to video and transcript covering topics like:
Varieties of Butternut Squash available
Starting seeds and caring for Butternut Squash
Fertilizer and/or Mulching
Transplanting best practices
Butternut Squash Companion Plants
Pests, Diseases and what to do about them
Harvesting and storing your Butternut Squash
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Ready for a growing horticulture adventure in butternut squash crop growing? Let's dive in!
Glossary of terms
Before we get started, let’s learn a little bit about butternut squash growing!
Separate male and female flowers that are on the same plant. For fruit production, pollen from the male flowers must be transferred to the female flower (mainly by insect pollinators). That’s why it’s very important to protect these beneficial insects.
The offspring of two plants from different breeds, varieties, or species.
A plant that has been pollinated by wind, insects, birds, humans, or by another natural source.
Butternut squash is a vining type, which is a plant that has trailing or climbing stems/ runners. Its vines need additional support like a trellis or fence in order to grow properly.
Varieties of butternut squash
These are just some of the many butternut varieties available!
This early variety grows in a bush habit, producing 1-2 pound fruit.
Ponca This variety is extra early, has a small seed cavity, and stores well
Ultra The largest fruit of this variety can be 6-10 pounds. It’s also got a good leaf canopy.
Zenith A hybrid variety that’s smooth with attractive fruit and a high yield.
Early Butternut A hybrid-All America Selection winner. It’s early, medium in size, and has a high yield.
Planting Butternut Squash
Butternut squash growing can either be directly sowed, or grown as a transplant.
Sow your squash seeds about 1 inch (2cm) deep.
You’ll want to sow 3 seeds in each spot, and then thin to the strongest plant.
Give your butternut squash some extra room by spacing them a minimum of 36-48 inches (90-120 cm) apart in rows that are 48-72 inches (120-180 cm) apart.
Their ideal soil pH is between 6.0-6.8, and they typically take about 10-14 days to germinate.
Squash can be transplanted when the plants are young (15-20 days old) and have been started in containers.
Keep in mind that vine crop transplants won’t do very well if the plants are too large.
To start your transplants, place two seeds in a 3-4 inch (7-10 cm) deep pot in late March/ early April.
Then, set up protective row covers as soon as you’re done planting.
Caring for butternut squash
In this section, I’ll tell you everything you need to know about thinning, weeding, watering and pollination. I’ll also talk fertilizer and mulch, transplanting, companion planting, and your growing structure options!
You’ll want to thin from 3 plants per hill to 1, which will avoid overcrowding your squash. That way, they have lots of space to grow with enough air circulation between them.
Make sure you keep weeds under control during your squash’s growing season. Weeds compete with plants for water, space, and nutrients - so either cultivate often, or use a mulch to prevent weed seeds from germinating.
Squash needs lots of moisture to produce high yields of quality fruit.
Typically, about 1 inch of water is needed each week during their fruit production.
In sandy soils, higher amounts of water might also be needed along with more frequent watering – for example, three quarters of an inch of water roughly twice a week.
Squash has both male and female flowers that grow the same plant.
Male flowers form first, followed by the females – which can be identified as having undeveloped fruit at their base.
Pollination is always necessary for winter squash, with pollen being transferred from male to female flowers by bees.
Avoid using any insecticides on your squash plants, because the chemicals can harm these pollinating bees – which wouldn’t be good for your squash!
Squash vines are sprawling and need plenty of space to grow, so they can be trained to grow on a trellis or fence.
These structures keep the stems and vines from snapping, which could result in disease or even death.
As your seedlings grow, remove any blossoms as they bloom. This will help encourage your plant to grow more squash.
As the buds of your squash start to grow, be sure to place a piece of wood under them - or just take care to move them so that rot doesn’t happen.
Keep in mind that any contact with the wet ground for a prolonged period of time can encourage rot diseases.
FERTILIZING AND MULCHING
Butternut squash growing with food and protection needed to grow large crops
FERTILIZING BUTTERNUT SQUASH
Use 1 cup of a complete organic fertilizer, working it into the soil beneath each plant.
For the best yields, you can also incorporate some compost or well-rotted manure before planting.
Fertilize your vegetable garden by scattering 2 pounds of a 10-10-10 fertilizer per 100 square feet of home garden, incorporating it into your soil.
If you’re planting transplants, then you’ll want to apply a transplant fertilizer starter when you plant.
Mix one tablespoon of a soluble fertilizer that’s high in phosphorus (10-20-10) into a gallon of water, then apply one cup of solution to each plant.
Squash plants have a shallow root system, so mulches help retain soil moisture while keeping soil temperature even.
Plastic mulch and fabric row covers (AG-19 grade) can help your plants get established while repelling insect pests during the seedling stage.
TRANSPLANTING BEST PRACTICES
Before you plant, you’ll want to harden-off your seedlings first, starting about 4–7 days before you’re ready to plant.
Get your seedlings used to the outdoor conditions by setting them outside for a few hours each day, keeping them sheltered from the elements at first. This will reduce their shock and stress from transplanting.
Once they’ve been hardened-off, create a mound that’s at least 3 inches tall and a minimum of 3 times the width of the roots.
Squash can be transplanted when the plants are young (15-20 days old) and have been started in containers. Be sure to handle your transplants gently and avoid disturbing their roots.
GROWING STRUCTURE OPTIONS
Choose a sunny spot and prepare 3-foot-wide planting hills within wide rows.
You can also position these hills along your home garden’s edge, leaving about 5-6 feet between hills.
Loosen the soil to at least 12 inches deep. Then, thoroughly mix in a 2-inch layer of mature compost as well as a light application of balanced, organic fertilizer.
Finally, be sure to give them a nice drink of water.
This option will work as long as your containers have plenty of drainage holes and lots of room.
As a rule of thumb, don’t use a container that’s any less than 5 gallons in size, for 2-3 seedlings.
During the growing season, feed your plants lightly to make up for the lack of nutrients in the potting soil.
COMPANION PLANTS DO’S AND DON’TS
Beans, corn, cucumbers, icicle radishes, melon, mint, onions and pumpkin are all great companion vegetables for your squash.
If you’re looking for some helpers with your butternut squash growing, borage deters worms while improving growth and flavor.
Marigolds deter beetles, and oregano provides some general pest protection. Dill might also help repel squash bugs, which are pests that kill your squash’s vines.
Broccoli, Brussels sprouts, cabbage, cauliflower, collard, kale, potatoes, Swiss chard, kohlrabi, and sweet potatoes should all be avoided near your butternut squash plant.
Common challenges and their solutions
Butternut Squash growing can bring attract pests and diseases that can potentially harm your butternut squash plants. Not to worry – I’ve listed them below, as well as how to either avoid or fix the problem.
Butternut squash growing minus the pests
These pests are usually a problem for the undersides of leaves and/or stems of your plant. They tend to feed in groups on the undersides of branches – and often spread diseases.
Solution: Use a strong jet of water to wash them off your plants.
Neem oil, insecticidal soaps, and horticultural oils are also effective against aphids. Just be sure to follow the application instructions on the packaging!
Oftentimes, you can also get rid of aphids by wiping or spraying the leaves with a mild solution of water and a few drops of dish soap (one variation includes adding a pinch of cayenne pepper).
Soapy water should be reapplied every 2-3 days for about 2 weeks.
Heavy feeding by these young larvae leads to skeletonized leaves.
Solution: Release their natural enemies to manage armyworm infestations. There’s also certain types of bacteria you can use to control these pests.
Brightly colored pests with either a green-yellow body with black spots, or alternating black and yellow stripes. These pests stunt the growth of seedlings and damage leaves, stems and/or petioles (the stems of leaves that attach to the bigger plant stem).
Solution: You can use floating row covers to protect your plants from damage - but these will need to be removed once your plants are flowering, to allow bees to pollinate.
You can also try applying kaolin clay, which can be effective against small numbers of beetles.
Small black beetles that feed on seedlings and jump when disturbed. The damage from their feeding habits can kill your seedlings off entirely.
Solution: Use a lightweight floating row cover at the beginning of the season to prevent them from becoming an issue.
You can also try a homemade spray using 2 cups of rubbing alcohol, 5 cups of water, and 1 tablespoon of liquid soap. Test out this mixture on a single leaf first, let it sit overnight, then spray the rest of your plant if you don’t notice any side-effects.
Dusting your plants with plain talcum powder can also help, as well as using white sticky traps to capture these pests as they jump.
These pests cause leaves to turn speckled, yellow, and brown. Plants wilt, runners die back, and the squash fruit can either become spotted or it dies.
Solution: Destroy all crop residue as soon as possible, either after harvest or after your plant dies.
Also, apply row covers when planting and use insecticidal soap.
Small gray grubs that can be found curled under the soil. They chew on stems, roots, and leaves.
Solution: Hand-pick any larvae after dark, and place a 3-inch paper collar around the stem of your plants. Keep your vegetable garden free of weeds too.
Also, you can try sprinkling wood ash around the base of your plants to keep these pests away.
These pesky flies will group together on the undersides of leaves and fly up when disturbed.
Solution: Remove any affected leaves, or the whole plant if it’s severely infested. Introduce beneficial insects into your vegetable garden, use yellow sticky traps, and apply insecticidal soaps or oils.
Keep in mind that these oils (like neem oil) might reduce whitefly numbers, but they won’t eliminate them entirely.
Butternut squash growing without common diseases
ALTERNARIA LEAF BLIGHT
Small, yellow-brown spots with a yellow or green halo will first appear on the oldest leaves.
As the disease progresses, leaves will begin to curl and eventually will die. This disease is common in growing areas with high temperatures and frequent rainfall.
Water your plants from below to avoid having soil splash up onto the lower leaves.
If you can water from below using a soaker hose or drip irrigation AND provide a well-ventilated cover for your plants to protect them from the rain, you’ll be all set.
Be sure to clean any equipment between uses to prevent the spread of bacteria, and do not prune or handle your plants when they’re wet.
Also, establish a crop rotation and stick to it. If you do spot some blighty leaves (usually on the bottom of the plant closest to the soil), remove and destroy them.
CERCOSPORA LEAF SPOT
Small spots with light to tan centers will first appear on the older leaves of your plants. As the disease progresses, the centers of these lesions might become brittle and could possibly crack.
Solution: You can try spraying your plants with a baking soda solution (one tablespoon of baking soda, 2.5 tablespoons of vegetable oil, and a teaspoon of liquid soap to one gallon of water).
Keep in mind that baking soda might burn some plant leaves – so you’ll want to spray one or two first, and then check for a reaction before applying every two weeks.
You can also spray neem oil, just make sure not to use it when pollinating insects (like bees) or other beneficial insects are around your plants.
Also, you can apply sulfur sprays or copper-based fungicides weekly at the first sign of this disease to prevent its spread.
These organic fungicides will not kill leaf spot entirely, but they will prevent the fungal spores from germinating and spreading.
Small yellow areas and irregular brown lesions will appear on the upper leaf surface, while gray mold grows on the lower leaf surface.
Solution: Plant resistant varieties when possible, prune or stake your plants, and remove any weeds to improve air circulation.
Water your plants early in the morning or use a soaker hose, which gives your plants time to dry out during the day.
Also, keep the ground under any infected plants clean during the fall and winter to prevent the disease from spreading.
Be sure to remove and destroy any plants with a serious infection.
Keep in mind that downy mildew is much easier to control when a plant’s leaves and fruit are kept protected by a copper spray.
You can begin treatments two weeks before the disease normally appears, or when you’re in for a long period of wet weather.
You can also begin treatments when the disease first appears, then repeat at 7-10 day intervals for as long as you need to.
FUSARIUM CROWN AND FOOT ROT
The wilting of leaves eventually progresses to the wilting of your entire plant – which then dies within a few days. When an infected plant is uprooted, it will have a distinct brown rot on the crown and roots. Also, plants will break easily below the soil line.
Solution: Plant resistant varieties when possible.
Fusarium thrives in hot temperatures when the soil moisture is low, so because of this, make sure to keep your soil evenly moist especially in the hottest months of the season.
Try to do so without flooding your vegetable garden, which can create a breeding ground for other diseases and pests.
Solarizing any affected soil can also help to kill off this fungus - simply cover the affected soil with black plastic and leave it undisturbed during the warm season.
The sun, along with the plastic, will then heat up the soil – killing the fungus in the process.
This fungal disease happens on the tops of leaves in humid weather conditions. Leaves will have a whitish or greyish surface and might also curl.
Solution: Avoid this disease by spacing and pruning your plants to provide good air circulation.
Use a thick layer of mulch or organic compost to cover the soil after it’s been raked and cleaned, while will help prevent the disease spores from splashing back up onto the leaves.
Milk sprays, made with 40% milk and 60% water, are an effective home remedy you can try. For best results, spray your plant leaves as a preventative measure every 10-14 days.
Also, you can occasionally wash the leaves of your squash to disrupt the daily spore-releasing cycle.
Neem oil and PM Wash, used on a 7-day schedule, will also help prevent fungal attacks on plants grown indoors.
Finally, water in the morning so that plants have a chance to dry out during the day.
Drip irrigation and soaker hoses are both great options that will help keep your plant leaves dry.
Symptoms will first appear on immature fruits as small light brown spots close to the blossom end of the fruit. As the fruit grows, the spots enlarge, turning into dark leathery lesions that are sunken into the fruit.
Solution: Maintain consistent watering, and keep your soil evenly moist. Mulch your plants to help them retain water – straw or black plastic will do the trick!
Excess nitrogen also causes blossom end rot on butternut squash, because it blocks the absorption of calcium. As a result, you’ll want to avoid high nitrogen fertilizers as well as ammonia fertilizers (like fresh manure).
If your plant is already showing signs of end rot in its early fruiting phase, you might have to add calcium into the soil.
Keep in mind, though, that calcium isn’t taken in well by the leaves - so avoid using a foliar spray.
Calcium needs to go directly to the roots, so calcium carbonate tablets (or anti-acid tablets like Tums) can be placed into the soil at the base of your plant.
CUCURBIT YELLOW STUNTING DISORDER VIRUS
Yellow to brown spotting typically appears first, which eventually leads to severe yellowing. Infected leaves might roll upward and become brittle, while the infected plant can appear stunted.
Solution: Since this disease is mainly spread by whiteflies, you’ll want to make sure you control their numbers.
Also, maintain healthy and vigorous plants. When possible, plant recommended varieties and monitor your garden for any unusual symptoms as they happen.
Keep your garden area clear of weeds, because they can harbor pesky insects.
Choosing separate areas for early and late plantings can also help to minimize the severity of the disease in those late plantings.
TIPS FOR MANAGING DISEASES
Butternut squash growing without diseases
Plant fungicide-treated seeds when possible.
Squash should be rotated with another crop every 2 years.
Crop debris should be removed from your garden as quickly as possible after harvest, or plowed deeply into your soil. Also, sanitize your equipment regularly.
Water your plants from their base rather than from above to reduce periods of leaf wetness – the longer leaves are wet, the more diseases will develop and spread.
Do not overcrowd your plants. Space them properly, allowing for good air circulation and an even amount of sun exposure.
Harvesting and storing
Butternut squash growing for your dinner plate and pantry
Butternut squash fruit is ready for harvest when the outside of the rind has turned a light tan to golden yellow.
That surface will then be difficult to pierce with your thumbnail, and the fruit will weigh between 2-5 pounds.
Cut the stem about 1-2 inches from the fruit. Make sure to harvest all mature fruits before hard frosts are set to arrive.
Store your butternut squash fruite in a dry location that has a temperature between 55-60°F (12-15°C). When stored under these conditions, your squash will keep for several months!