Growing Zucchini: What You Need to Know

Zucchini is a classic summertime vegetable that’s easy to grow in your own garden. Started from seeds, these plants produce a bumper crop of tender summer squash with little specialized attention.


What type of zucchini should I plant?

There are dozens of zucchini varieties to choose from. Since zucchini grows best from seeds rather than seedlings, you’ll don’t have to limit yourself to what’s available at the local garden center. Many organic and heirloom seed companies offer varieties of zucchini that grow in unusual shapes and colors, as well as those that thrive in a variety of environments.

In choosing a type of seed, consider how large the plants will grow in relation to the space you have available, how long your growing season is, and what diseases and pests are common in your area. Check out specific varieties to determine which is best for your particular garden

How much sunlight do my zucchini need?

Zucchini need full sun to produce well. That means a minimum of six hours of light per day.

What kind of soil do zucchini prefer?

Choose a well-drained site for your zucchini. Good drainage will help prevent powdery mildew, a fungus that thrives in damp conditions. Another way to help prevent pests and disease is to blend a rich compost mixture into your soil before planting. The beneficial microbes in the compost will help crowd out their problem-causing cousins, and add valuable nutrients to your soil.

What should I avoid planting with zucchini?

Zucchini are a type of squash, which means they can easily cross-pollinate with other varieties. Fortunately, that doesn’t cause a problem for this year’s crop. If you save seeds, however, you’ll want to limit yourself to one variety of squash at a time.

You can also limit the carryover of pests and diseases from year to year by moving your zucchini and other squash to a different area of your garden each season. Though this kind of crop rotation does not eliminate diseases or pests lingering in the soil of your garden, it does minimize the chance of reinfecting your new seedlings.

When should I plant?

Wait to plant your zucchini seeds until soil temperatures have reached 60°F (15°C). Zucchini are not tolerant of cold, so if a late frost threatens, be sure to use row cover to shield your young plants from damage.

Because some varieties of zucchini begin to produce in as few as 45 days, you can delay your planting well into the summer as long as your growing season allows it. This can help limit the impact of some pests, depending on where you’re located.

How do I plant zucchini seeds?

If you’re growing your zucchini from seed, you can either sow them in rows or group them in “hills.” For rows, sow seeds 1 inch (2 cm) deep at least 24 inches (61 cm) apart for compact plants and at least 36 inches (91 cm) for sprawling varieties. You can plant the seeds in pairs and thin them once the plants have developed their first set of leaves to avoid gaps in your row.

  • To plant hills, mound up soil into a hill roughly 10 inches high and 12 inches in diameter (25 by 30 cm).
  • Create a shallow depression in the top of the hill to help hold water for the germinating seeds and plant 4-5 seeds 1 inch (2 cm) deep.
  • Once the plants have emerged and develop their first leaves, thin to 2-3 plants per hill.
  • Space your hills at least 24 inches (61 cm) apart.

What type of fertilizer should I use?

Zucchini are “heavy feeders,” which means they like a nutrient-dense soil. Start them off right by blending compost into your garden soil before planting. While most varieties will produce well without additional feedings, an added boost of nutrients during the growing season doesn’t hurt, and can help fend off some types of disease.

If a heavy harvest is what you’re after, use a fertilizer blend with extra phosphorous. A mix with added calcium can help prevent blossom-end rot. Water-soluble mixes like fish emulsion are an excellent choice, as are granular fertilizers that can be scattered around the plants. If you choose to use synthetic fertilizers, be sure to follow the dilution instructions very carefully. These pose much more risk of harming your plants if overused.

How often should I water my zucchini plants?

Regular watering is crucial to developing healthy plants and a good crop. Make sure your plants get about an inch (2 cm) of water per week, either from rain or from irrigation. Avoid overhead irrigation like sprinklers or spray from a hose. Wetting the leaves promotes disease like powdery mildew. Instead, use a soaker hose or drip irrigation to water directly at the plants’ roots.

What do I do if my plants get powdery mildew?

This very common fungal infection covers the plant’s leaves in a sticky white powder like soap scum. As the infection progresses, the leaves turn yellow, wilt, and eventually shrivel and die. Prevent powdery mildew by practicing crop rotation and avoiding overhead watering. At the first sign of infection, treat your plants with a copper fungicide or neem oil, and carefully remove and dispose of severely affected leaves. Advanced infections are almost always deadly to the plants.

What is fusarium wilt?

Another common fungal disease in zucchini plants, the fusarium fungus enters plants through their roots. This clogs the tiny vessels that carry water and nutrients throughout the plant, causing it to quickly wilt and die. Fusarium fungus is almost impossible to eliminate once it has infected your garden. Avoid infection by carefully inspecting purchased seedlings for signs of disease, and never compost any diseased plant material, as this provides the perfect environment for the fungus to grow and multiply.

Can my zucchini plants get squash mosaic virus?

As members of the squash family, zucchini plants are indeed susceptible to squash mosaic virus. This disease usually develops in one of two ways. Either the seed was already infected before you even planted it, or the disease was brought to your garden by cucumber beetles carrying the virus.

The bad news is that the mottled coloration, distorted leaves, and stunted fruits caused by the disease are incurable. The good news? By buying your seed from a reputable company and controlling cucumber beetles in your garden, you can greatly reduce the likelihood that your plants will ever be infected.

What is squash wilt?

Another disease carried by cucumber beetles, squash wilt is an incurable bacterial disease that causes the entire plant to wilt and die. Again, keeping an eye out for cucumber beetles will reduce the risk to your plants, but once they’re infected, the best course of action is to promptly remove affected plants before the disease can spread.

What is Blossom End Rot?

Blossom end rot is a very common problem, but isn’t actually a disease at all! If you notice the ends of your zucchini getting squishy and rotting while they’re still on the vine, the likely culprit is blossom end rot, also known as calcium deficiency. Avoid the issue altogether by adding a bit of gypsum or oyster shells to your soil when preparing to plant. If you do notice problems during the growing season, remove the affected fruit and feed your plants with a low nitrogen, calcium rich fertilizer.

What types of squash pests should I look out for?

There are several types of insects that particularly enjoy feeding on zucchini plants. Keep an eye out for these destructive pests.

Cucumber beetles:

As if the diseases they carry weren’t enough! Cucumber beetles love to chew on the leaves, stems, flowers, and fruit of squash plants like zucchini, and the larvae destroy the roots. A severe infestation can wipe out your plants before diseases even have time to set in!

Thankfully, both types of cucumber beetles are immediately recognizable. They are long-bodied and orangish to yellowish green with distinctive black stripes or spots, depending on the variety. Row cover can deter these beetles, but if you need to treat with insecticides, opt for an early evening treatment to get the most beetles and the fewest beneficial insects.

Squash bugs:

Relatives of the stink bug, these little vampires wreak havoc on your squash plants by using their sharp, straw-like mouthparts to suck nutrients straight out the stems and fruits. This damage causes spotting and wilting of leaves, and rotten or mushy spots in fruits. Since squash bugs are relatively large, traps can be an effective way to control their numbers. If you must use a pesticide, neem oil is a good option. Apply it to the undersides of the leaves for best results.

How do I harvest my zucchini?

When you harvest your zucchini depends a bit on personal preference and on which varieties you’ve chosen to grow. Typically, smaller zucchini are more tender and have fewer seeds than their larger counterparts, but some varieties can be left to grow quite sizeable before picking.

To harvest your zucchini, use a sharp knife to slice each fruit free. Cool them quickly for maximum shelf life, and store them in the refrigerator until you’re ready to enjoy!