Growing and Caring for Summer Squash

By Charlie Nardozzi

There was a time when growing summer squash meant either growing a yellow crookneck or a green zucchini. Times have changed. There are not only new varieties of yellow summer squash and green zucchini available that feature better productivity and disease resistance, there is also a host of other summer squash varieties that have different shapes and skin colors.

Summer squash is one of the simplest vegetables to grow. The large seeds germinate quickly in warm soils. The plants grow fast, they stay in a bush form so they are more manageable, and they often flower within a month after seeding. And the fruits just keep coming all summer until disease, insects, or you stop them. In fact, their reputation for being so prolific leads many people to keep their car windows and house doors closed for fear neighbors will dump their excess squash on them!

Although they produce abundantly, summer squashes also taste great and make perfect additions to sautes, stir fries, soups, casseroles, and breads.

Types of Summer Squash

There are three basic categories of summer squash to choose from when deciding what to plant -- straight neck yellow squash, crookneck yellow squash, and green zucchini. Within each category there are variations in size, shape, and color. Some varieties are hybrids, while others are open-pollinated. Hybrids offer traits like uniformity and long production, while many open-pollinated varieties have excellent old-time flavor and are a must if you'd like to save seeds. All are bushy, rather than vining, so they are a great choice for space-strapped gardeners. You can even grow summer squash in containers; use a pot that contains at least five gallons and is at least 10 inches deep.

 The yellow crooknecks are one of the most common types grown. Hybrid varieties, such as 'Dixie' and 'Horn of Plenty', improve on the heirloom crookneck varieties with better production and uniformity. Some varieties, such as 'Supersett', have improved disease resistance and uniform fruit color.

If you like yellow summer squash but not the crookneck shape, try some of the straight-neck yellow summer squash. 'Goldbar', 'Gold Rush', and 'Multipik' are newer varieties to try.

Zucchini varieties abound. 'Black Beauty' and 'Grey Zucchini' are two classics. Others to try include 'President' and 'Senator'. For a lighter green zucchini, try the Lebanese, "cousa" type such as 'Magda'.

For a squash of a different shape try the patty pans. These "flying saucers" are similar to other summer squash except for their unique shape. 'Peter Pan' is a hybrid, green, scalloped-shape variety; 'White Bush Scallop' is a white version, and 'Sunburst' is a yellow variety. For something completely different, try 'Eight Ball', a hybrid, round squash that is great for stuffing and baking.

Summer Squash Planting and Growing Tips

Like all squash and pumpkins, summer squash and zucchini grow best with warm soil temperatures and plenty of water. Although they can be bought as transplants from a garden center, summer squashes are easiest sown direct into the soil once the soil temperatures is above 60° F. In cold weather areas, consider laying down a layer of black plastic mulch two weeks before planting to preheat the soil and then plant into holes poked in the plastic. Amend the soil with a 1- to 2-inch-thick layer of compost before planting.

There are various planting methods you can use. Plants seeds in rows, dropping the seeds about 8 inches apart in furrows about 6 inches deep. You also can plant summer squash in hills or mounds. Plant 6 to 8 seeds in hills or circles spaced 4 feet apart. Thin after the seedlings emerge, leaving the two to three strongest seedlings. If you have heavy or wet soil, raise the hills into mounds about 8 inches high and flat on top. Plant and space the seeds as you would in the hills.

Once they start growing, side-dress plants at first flowering and then monthly with an all-purpose fertilizer to keep the fruits coming. Keep plants well weeded, and once the soil has warmed, mulch with an organic product, such as pine straw. Keep the squash well watered as well.

Squash Pollination

Most summer squash varieties have separate male and female flowers. Insects, especially bees, are needed for pollination and fruiting to occur. During periods of cold, cloudy weather, the bees may not be flying, and this can result in reduced pollination and fruiting. You can improve the harvest by helping with pollination. In the morning when the flowers are fully opened, go into the garden and swish a cotton swab in the male flower (the one without the enlarged area or ovary behind the flower). Then take the cotton swab containing the yellow pollen and swish it around the female flower (the one with the enlarged ovary behind the flower). This should help insure that the flower gets pollinated, and young squash are bound to follow.

Pests and Diseases

Summer squash is attacked by the same insects that love winter squash and pumpkins. Squash vine borer adults lay their eggs on the squash stems near the ground. The eggs hatch and the young tunnel into the fruits and can eventually kill the plant. Protect your squash plants by covering them with a floating row cover until they start to flower. Place aluminum foil beneath the plant to confuse the adult flies so they can't lay eggs. Surgically remove the young larvae with a sharp knife or inject Btk (Bacillus thuringiensis var. kurstaki) into the plants.

Squash bugs: These drab brown insects, about 1/2 inch long, can be a big headache for squash growers. They seem to be especially fond of yellow summer squash varieties. Squash bugs feed by sucking, causing leaves to wilt and die. Look for and crush clusters of small, shiny, orange-brown eggs on the undersides of leaves. And keep and eye out for the immature nymphs, which look like big gray aphids. Handpick the adults and nymphs and drop them into a container of soapy water to drown; the adult bugs will give off an unpleasant odor if crushed. Keep the area at the base of plants free from mulch, as it can provide a protected spot for the bugs to congregate. Spraying an insecticide such a pyrethrin in this area can help control this pest.

Powdery mildew: This fungal disease is a common affliction on summer squash. It covers leaves with a powdery white coating that can cause them to eventually wither and die. Humid conditions promote this disease, so make sure plants have good air circulation around them. Handpick infected leaves as soon as you notice them and clean up all plant debris well at the end of the season to reduce the amount of overwintering fungi. Spraying the plants with a mixture of one part milk and nine parts water may slow the spread of the disease. If you spray with a material labeled for powdery mildew control (there are both both organic and non-organic options), begin at the first sign of the disease, since the sprays provide prevention and suppression, not a cure.

Cucumber beetles: These little critters are the number one threat to squash plants (and other members of the Cucurbit Family). The black and yellow striped or spotted beetles feed on young seedlings. They are also the Typhoid Mary's of the garden, transmitting a deadly bacterial wilt as they feed. Row covers placed over young seedlings will offer protection, but need to be removed once plants begin to flower so that bees can get in to pollinate the blossoms. Kaolin clay is a natural product that will repel beetles from feeding on plants. You can also set up yellow sticky traps to capture the adult beetles. In among your squash plants, place pieces of waterproof material painted yellow and coated with sticky material like Tanglefoot.

Harvesting Squash

Summer squash fruits are best harvested when young and immature, unlike winter squash and pumpkins whose fruits need to mature on the vine before harvest. Begin picking summer squash even while the flower is still attached. The ideal size is 6 to 8 inches long. The more you harvest, the more the plant will produce. Don't let squash get overgrown. Not only will you be at a loss as to what to do with the giant fruit, it will slow down the production of additional squash. If you harvest fruits with a short piece of the stem attached, they will last longest in the refrigerator.