Zucchini, crookneck, patty pan, the varieties of summer squash are endless. One of the more popular annual summer vegetables, summer squash, can be planted throughout the United States at any time after the last frost date when the soil temperature 4 inches down has reached 60° F. A black plastic mulch will help to warm the soil sooner.
Seed can be planted in full sun 4-6 inches apart in rows 3 feet apart at a depth of one half inch. Summer squash thrives best when temperatures average between 65° F and 75° F. Thin the seedlings to 12-15 inches apart when the first pair of true leaves appears.
Another way to cultivate summer squash is to plant the seeds in low hills spaced 3 to 4 feet apart in rows 4 to 6 feet apart. 2 or 3 seeds to each hill is best.
Test your soil to determine your fertilizer needs. pH should be between 5.8 and 6.5 for best results. It is also important to maintain adequate levels of calcium in the soil as too little can cause blossom end rot in the fruit. Applying the recommended amount of lime just before planting is essential to a healthy crop. Too much nitrogen will cause excessive vine growth to the detriment of the fruit growth. Too much nitrogen also inhibits proper intake of calcium by the plants.
Water your plants in the morning to allow the leaves enough time to dry before nightfall. To prevent shallow root systems from developing, water to a depth of 6 inches two to three times per week, more often during drier periods. The most critical time to maintain a proper water supply is when fruit is setting and developing.
Provide an organic mulch 2 to three inches deep for your plants. This will help to retain moisture in the soil and allow the roots to take in calcium more efficiently.
For proper fruit growth, squash blossoms must be pollinated by bees. Separate male and female flowers are present on all squash plants, but pollen must be transferred between them for fruit to set. Look for bees around your plants when blooming begins. Avoid using insecticides on squash plants until late in the evening when bees are no longer active. Improper pollination of summer squash results in poorly shaped fruit.
You can begin to harvest most squash varieties 55 days after planting. Harvest fruits when the skins have a glossy appearance and are tender when slightly pressed. Harvest the fruits every day or every other day. Scallop (patty pan) squash should be harvested when the fruits are 3 or 4 inches in diameter. Zucchini fruits should be 7 or 8 inches long when harvested. Yellow crookneck and straight-neck squash should be harvested when the fruits are 1 1/2 to 2 inches in diameter.
Large hard fruits should be removed and discarded. Leaving them on the plants will discourage further fruiting. Store harvested summer squash in the refrigerator and use or process within one week.