As a summer variety, zucchini is harvested before its rind hardens (unlike winter squashes). It can be consumed either raw or cooked and is very high in potassium. It’s a versatile and delicious vegetable, making a great addition to all your favorite dishes!
To help ensure your Zucchini thrives, we’ve put together this how-to video and transcript covering topics like:
Varieties of Zucchini available
Starting your Zucchini seeds
Caring for Zucchini at all stages
Fertilizer and/or Mulching
Transplanting best practices
Companion Plants do’s and don’ts
Common challenges and Their Solutions
Pests, Diseases and what to do about them
Harvesting and storing your Zucchini
Why Zucchini is called summer squash
In addition to describing the planting time, “summer squash” refers to their short storage life, unlike that of winter squashes. Summer squash grows on non-vining bushes.
Varieties of zucchini squash
Check out all your options!
A medium green variety that’s compact and grows as an open bush.
Aristocrat: A waxy medium green variety. Black Zucchini, Best known as summer squash, has green-black skin and white flesh.
Black Beauty: A slender, dark black-green variety with slight ridges.
Chefini: A glossy, medium or dark green in color zucchini.
A long, slender variety that’s dark green overlaid with light green stripes.
VEGETABLE MARROW WHITE BUSH
This variety is creamy-greenish in color with an oblong shape.
This variety is deep gold in color, with superior fruit quality.
Starting your seeds
Transplanting is possible, but direct seeding is best when starting squash.
Summer squash likes warm soils, and it’s susceptible to frost - so don’t rush to plant early in the spring.
Wait until all danger of frost has passed and your soil has warmed up to about 70°F, which is roughly two weeks after the last frost.
Sow your seeds about a half-inch deep, planting 2-3 seeds every 2-3 feet in the row.
After they’ve emerged, cut the extra plants with scissors, leaving only the single most robust plant.
Then, thin seedlings stand 8-12 inches apart. A “hill” of 3-4 seeds sown closely together is another way to plant your squash in the garden; just make sure to allow 5-6 feet between hills.
You can also sow your squash seeds indoors using 3-inch diameter containers.
If you choose this option, you’ll want to start your transplants about three weeks before planting time.
Both seeds and transplants can be planted through black plastic to speed up their maturity.
If using transplants, be sure to handle them gently and avoid disturbing their root system.
Caring for Zucchini Squash
In this section, we’ll tell you everything you need to know about ideal growing conditions, how to water and weed your zucchini squash, and how to mulch and fertilize it. We’ll also talk transplanting, companion planting, and your growing structure options.
For germination, zucchini squash prefers temperatures that are between 60-105°F.
They won’t germinate in cold soil, so you’ll want to wait to plant until your soil reaches at least 65°F -- preferably 70°F or more, while it germinates best at 95°F.
Their ideal soil pH is between 6.0 - 7.5, but it will grow in soils with a pH of up to 8.0.
Typically, zucchini squash takes about 5-10 days to germinate.
An insect (like bees) must move pollen from the male flowers to the female flowers. Cold, rain and cloudy weather can hurt their pollination efforts… so if you have tasteless fruit, that could be due to dark cloudy weather.
Note: Many squashes will produce male flowers for 1-2 weeks before you notice the first female flower.
This is a normal growth habit, and it varies with different varieties.
The female flowers, which open later, have a swelling at their base, which forms the fruit (also known as the ovary).
Water your zucchini squash deeply and regularly at the base of each plant.
It’s essential to water them during hot, dry weather and once the first fruits start to form.
Remove all young weed seedlings either by hand or with a hoe and use a mulch around plants to keep weed seeds from growing.
FERTILIZING AND/OR MULCHING
Side-dress with a quarter pound of a 10-10-10 fertilizer per 10 feet of row.
You’ll want to do this about four weeks after blossoming begins.
Soil with plenty of compost or well-rotted manure is ideal, but good crops can also grow in average soils that have been fertilized enough.
Zucchini squashes are also heavy feeders, which means you’ll want to prepare your planting bed with lots of organic matter.
Use a few inches of aged compost, spread it across the bed, and turn it under.
If your plant leaves become pale or your plants seem weak, side-dress your zucchini with well-aged compost.
You can also use a foliar spray of liquid fish or kelp fertilizer—make sure it’s high in phosphorus for good fruit production.
Also, please don’t use a fertilizer that’s too high in nitrogen because it will reduce your yield.
Use row covers to protect your plants early in the season and prevent insect problems. Be sure to remove this cover before flowering so that bees can pollinate your plants.
You’ll also want to remove it when hot weather arrives so that your zucchini squashes aren’t exposed to too much heat.
Mulching your plants helps to retain moisture and suppress any weeds.
Also, mounding soil around the base of your plants can discourage squash borers from laying their eggs – which would become a problem for your squash later on.
TRANSPLANTING BEST PRACTICES
Before you transplant, make sure to harden off your seedlings by cutting back on their water and reducing their temperature.
Then, set them outside for a few hours each day, keeping them sheltered at first.
This helps prepare them for outside living, reducing the risk of transplant shock and stress.
GROWING STRUCTURE OPTIONS
CONTAINERS FOR TRANSPLANTS
In general, 3-inch diameter containers will work for growing your transplants.
Zucchinis need large containers to accommodate them, as well as frequent watering.
SPUN ROW COVERS
They raise the air temperature around your plants and protect them from cold nights. Row covers also keep away insects – the bad and the good – so once your squash starts to flower, be sure to remove these covers so that bees and other beneficial insects can pollinate your plants.
PLASTIC MULCH COVERS
Earlier planting is possible if you use black plastic mulch, which raises the soil temperature since the black color of the mulch will absorb heat from the sun.
Apply black mulch after you prepare your soil in the spring. Simply cut holes or slits in the mulch, then plant your seeds.
After seedlings have emerged, position some row covers over your plants, securing the edges with soil or staples.
These can be set directly into the ground at planting time, which avoids disturbing the roots of your plant.
COMPANION PLANTS DO’S AND DON’TS
Radishes are good companion plants for zucchini, as radishes help repel common zucchini pests like aphids, squash bugs, cucumber beetles, and more.
Also, a few garlic plants tucked among your zucchini can help keep aphids and other pests in check.
Since zucchini plants are heavy feeders, legumes like beans and peas are beneficial because their roots fix nitrogen in the soil.
Herbs like peppermint, dill, mint, parsley, and oregano are also great companions for your zucchini.
Avoid planting your zucchini with the following vegetables: potatoes, broccoli, Brussels sprouts, cabbage, cauliflower, collard, kale, kohlrabi, and sweet potato.
Common challenges and their solutions
There are several pests and diseases that can potentially harm your zucchini squash. Not to worry – we’ve outlined them below, as well as how to either avoid or fix the problem!
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 water jet 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!
You can often 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 two weeks.
Heavy feeding by these young larvae leads to skeletonized leaves.
Solution: Release their natural enemies to manage armyworm infestations. There are 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 damaged 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.
Tiny black beetles 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 one 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 dieback, and the squash fruit can either become spotted or die.
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 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 garden free of weeds too.
You can also try sprinkling wood ash around the base of your plants to keep these pests away.
These pesky flies will group on the undersides of leaves and fly up when disturbed.
Solution: Remove any affected leaves or the whole plant if severely infested.
Introduce beneficial insects into your garden, use yellow sticky traps, and apply insecticidal soaps or oils.
Remember that these oils (like neem oil) might reduce whitefly numbers, but they won’t eliminate them.
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 die. This disease is common in growing areas with high temperatures and frequent rainfall.
Solution: 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 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 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; make sure not to use it when pollinating insects (like bees) or other beneficial insects are around your plants.
You can also 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 spots 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 severe 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 typically appears or when you’re in for an extended period of wet weather.
You can also start 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. An infected plant that is uprooted 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 garden, which can create a breeding ground for other diseases and pests.
Solarizing any affected soil can also help 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 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.
Spray your plant leaves as a preventative measure every 10-14 days for best results.
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 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 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 spaghetti 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 minimize the severity of the disease in those late plantings.
Harvesting and Storing
Harvest when your squash is still immature, once it’s about 6-8 inches long and 1.5-2 inches in diameter for elongated types.
If the rind is too hard to be pierced by your thumbnail, then it’s over-mature. If that happens, simply remove the old fruit to allow the new fruit to develop.
You’ll want to check your plants daily once they bear fruit. To speed up the first harvest by as much as two weeks, use some black plastic mulch to warm your soil before direct seeding or transplanting.
Early fruits are sometimes wrinkled and can turn black or even rot due to poor pollination.
Zucchini squash will keep for 5-14 days in cool (32°- 50°F) moist (90% relative humidity) conditions.
The longer you store summer squash, the more likely it can be damaged by the cold.
If it’s affected by the cold, it will develop pitted skin and water-soaked flesh.