Harvest summer squash before fruit matures.
Summer squash (also known as vegetable or Italian marrow), is a tender, warm-season vegetable that can be grown throughout the United States anytime during the warm, frost-free season.
Summer squash differs from fall and winter squash in that it is selected to be harvested before the rind hardens and the fruit matures. It grows on bush-type plants that do not spread like the plants of fall and winter squash and pumpkin. A few healthy and well-maintained plants produce abundant yields. Summer squash appears in many different fruit shapes and colors:
- Scallop or Patty Pan is round and flattened like a plate with scalloped edges, usually white but sometimes yellow or green.
- Constricted neck is thinner at the stem end than the blossom end, classified as either "crookneck" or "straightneck" depending on if the stem end is straight or bent, and is usually yellow.
- Cylindrical to club-shaped Italian marrows, such as zucchini, cocozelle, and Caserta, are usually shades of green, but may be yellow or nearly white.
The varietal selection of summer squash has markedly changed in recent years and the number of varieties offered has greatly expanded as the result of new interest, hybridization, and introduction of disease resistance. The number of varieties is staggering.
Growing Summer Squash
When to Plant
Plant any time after the danger of frost has passed, from early spring until midsummer. Some gardeners have two main plantings - one for early summer harvest and another for late summer and fall harvest.
Spacing & Depth
- Sow two or three seeds 24 to 36 inches apart for single-plant production, or four or five seeds in hills 48 inches apart.
- Cover one inch deep.
- When the plants are 2 to 3 inches tall, thin to one vigorous plant, or no more than two or three plants per hill.
Any well-drained garden soil produces excellent yields of summer squash. Certain mulches increase earliness and yields because the roots are shallow.
Cucumber beetles attack seedlings, vines, and both immature and mature fruits. They can be controlled with a suggested insecticide applied weekly either as a spray or dust. Be alert for an infestation of cucumber beetles in early September because these beetles can damage mature fruits.
Squash bugs attack vines as the fruit begin to set and increase in numbers through the late summer when they can be quite damaging to maturing fruit. They hatch and travel in groups, which seem to travel in herds until they reach maturity. Using the proper insecticide when the numbers of this pest are still small minimizes damage.
Squash vine borer will cause a plant to wilt seemly overnight. The adult is a beautiful clear-winged moth. It flies during the daytime and lays eggs singly at the base of the squash plants or on leaf petioles. The egg hatches in 7-10 days and the larva bore into the stem of the plant leaving a trail of waste behind where it feeds on the stem tissues.
- The damaged stem tissues cannot facilitate the translocation of water and nutrients. This causes the vine to wilt and the whole plant may eventually die.
- The infestation is more serious during the extended dry period in early summer.
- Squash that still vine can be kept alive by rooting the stem every foot or so along the vine.
The squash vine borer overwinters as a pupa in the soil near the former squash plant and appears again in mid-June to July the following year.
Harvesting Summer Squash
Because summer squash develops very rapidly after pollination, they are often picked when they are too large and overmature. They should be harvested when small and tender for the best quality.
- Most elongated varieties are picked when they are 2 inches or less in diameter and 6 to 8 inches long.
- Patty Pan types are harvested when they are 3 to 4 inches in diameter.
- Slightly larger fruit may be salvaged by hollowing out and using them for stuffing. These larger fruits may also be grated for baking in breads and other items.
- Do not allow summer squash to become large, hard, and seedy because they sap strength from the plant that could better be used to produce more young fruit.
- Pick oversized squash with developed seeds and hard skin and throw them away.
- Go over the plants every 1 or 2 days.
- Squash grows rapidly; especially in hot weather and is usually ready to pick within 4 to 8 days after flowering.
Although summer squash has both male and female flowers, only female flowers produce fruits. Because the fruits are harvested when still immature, they bruise and scratch easily.
- Handle with care and use immediately after picking. Be careful when picking summer squash, as the leafstalks and stems are prickly and can scratch and irritate unprotected hands and arms.
- Use a sharp knife or pruning shears to harvest and wear gloves if possible.
- Some gardeners also pick the open male and female blossoms before the fruits develop. Especially the female blossoms, with tiny fruit attached, are a delicacy when dipped in a batter and fried.
Selection & Storage
Most people harvest summer squash too late. Like winter squash, summer squash is an edible gourd. Unlike winter squash, it is harvested at the immature stage.
- Ideally, summer squash should be harvested at 6 to 8 inches in length.
- Pattypan and scallopini are ready when they measure about 3 to 4 inches in diameter or less.
- Tiny baby squash are delicious too.
- Large rock-hard squashes serve a better purpose on the compost heap than in the kitchen.
Cut the squash from the vine using a sharp knife or pruning shears to avoid damaging the plant. Summer squash vines are very prolific, the more you harvest the greater the yield. The most important characteristic to remember is that summer squash is best when immature, young and tender.
Because summer squash is immature, the skin is very thin and susceptible to damage. Handle with care. The average family only needs to plant one or two of each variety. Overplanting usually leads to hoards of huge inedible fruit and/or scouring the neighborhood for people to take the surplus.
To store summer squash, harvest small squash and place unwashed in plastic bags in the crisper drawer of the refrigerator. Wash the squash just before preparation. As with most vegetables, water droplets promote decay during storage. The storage life of summer squash is brief, so use it within two to three days.
Squash blossoms are edible flowers, raw or cooked. Both summer and winter squash blossoms can be battered and fried in a little oil for a wonderful taste sensation. Harvest only the male blossoms unless the goal is to reduce production.
- Male blossoms are easily distinguished from female blossoms. The stem of the male blossom is thin and trim. The stem of the female blossom is very thick. At the base of the female flower below the petals is a small bulge, which is the developing squash.
- Always leave a few male blossoms on the vine for pollination purposes. There are always many more male flowers than female. Harvest only the male squash blossoms unless you are trying to reduce production.
- The female blossom can be harvested with a tiny squash growing at the end and used in recipes along with full blossoms. Use the blossom of any variety of summer or winter squash in your favorite squash blossom recipe.
Use pruning shears or a sharp knife to cut squash blossoms at midday when the petals are open, leaving one inch of stem. Gently rinse in a pan of cool water and store in ice water in the refrigerator until ready to use. The flowers can be stored for a few hours or up to 1 or 2 days. If you've never eaten squash blossoms, you are in for a treat.
Questions & Answers
Q. Will summer squash cross with winter squash?
A. Summer squash varieties can cross with one another, with acorn squash and with Jack-o'-lantern pumpkins. Cross-pollination is not evident in the current crop, but the seed should not be sown for the following year. Summer squash does not cross with melons or cucumbers.
Preparing Zucchini for Exhibition
Former Illinois Extension Specialist Jim Schmidt demonstrates how to properly prepare zucchini for exhibition.