Summer Squash

Cucurbita pepo

by Master Gardener Stephanie Wrightson

Green zucchini is practically a staple in Sonoma County. By August, gardeners are in a panic trying to keep up with their prolific bounty. There even is a National Sneak Some Zucchini on Your Neighbor’s Porch day on August 8th. The secret is restraint – one, maybe two plants. Or choose a small bush or patio variety if feeding only one or two people.

Most summer squash are varieties of Cucurbita pepo. But not all Cucurbita pepo are summer squashes. There are a lot more choices than the standard green zucchini. There are not only dark green, grey, gold, striped, etc. zucchini, but also pattypan or scallop squash as well as yellow straightneck and crookneck squash. If you don’t have room for squash to wander, choose a patio or bush variety, or you can grow it upright on a frame on the north side of your bed. Compact or bush varieties recommended by the California Master Gardener Handbook include: ‘Peter Pan Hybrid’ (bush with miniature light green pattypan fruit), ‘Scallopini’ (bush with dark green speckled pattypan fruit), ‘Early White Bush’ (white pattypan), ‘Sundance’ (high-yield yellow crookneck), ‘Dixie’ (smooth skin yellow crookneck), ‘Greyzini’ zucchini and ‘Ambassador’ zucchini. Some varieties that require less water when established include: ‘Cocozelle’ (an Italian heirloom bush variety), ‘Costata Romanesco’ (a traditional Italian heirloom with heavy male blossom buds for cooking), ‘Dark Star’ (a big, tall variety with spineless stalks) and ‘Lebanese Light Green’ (a mild and tender bush variety). My favorite varieties are gold zucchini. The skin is tender and the flesh is sweet. For the past few years, I’ve grown ‘Gold’ or ‘Cube of Butter’ zucchini. But these can be as unwieldy as the wide-ranging stems of standard green zucchini. This year, I chose ‘Buckingham Yellow,’—a patio variety that should not overwhelm my community garden space. I also grow a round, tender French heirloom bush variety—‘Ronde de Nice’—and harvest them when they are two to three inches in diameter. These freeze well.

Plant squash starts as soon as the threat of frost passes—mid- to late-April in some county micro-climates. Many county gardeners wait until May. For a head start, seed indoors three weeks prior to the expected last frost. If you decide to direct seed when the weather is warm, plant two or three in a hill and, then, thin to the strongest seedling. If you leave them all, they will be overcrowded and prone to disease due to poor air circulation around the base of the plants. You transplant summer squash through July.

Amend the soil with compost before planting. Squash is a heavy feeder. You may need to side-dress with a little compost during the growing season but go easy on nitrogen that will cause green, leafy growth; fruiting will suffer and insects will be attracted to the lushness. An organic phosphorus fertilizer will promote fruiting.

While starting seed is easy, pollination is a little trickier. Plants have both male (pollen-producing) and female (fruit-producing) blossoms. Bees help pollinate by visiting both flowers. If you have blossoms and no fruit, use a cotton swab to move pollen to female blossoms (hint: female blossoms are swollen at the base—future squash—while male blossoms have longer, skinnier stalks). Varieties of Cucurbita pepo can cross-pollinate—not a worry when buying new seed each year. If you save seed, grow just one heirloom variety (it’s best to not save seed in a community garden where many varieties are grown).

Regular, even watering is key. Like tomatoes, squash is susceptible to blossom end rot caused by uneven watering and a calcium deficiency. Buy crushed oyster shells, or wash and dry egg shells and pulse them in the blender to make a calcium-rich powder. Use an organic mulch to retain moisture in the soil but keep mulch away from stems.

In my garden, spotted cucumber beetles can be a real problem. They can devastate seedlings, but larger plants can better tolerate some munching. One strategy is to cover seedlings with shade cloth to exclude insects. Remove the cover when blossoms appear so that bees can pollinate the plant. Mulch can reduce populations of these soil-residing beetles. Because these pests have two to three generations, another strategy is to stagger seed-starting indoors. Then, you will have replacement seedlings if the timing is wrong. I find that the beetles are slower in the morning—ifthe population isn’t heavy, you can hand-pick and drop them in a bucket of soapy water. For more information on squash pests, see the University of California’s pest notes.

Apparently, the world record is a Canadian-grown zucchini measuring 7 feet, 3 inches. Of course, for eating, we pick squash much smaller. In general, harvest zucchini when 6-8 inches, pattypan when 3-4 inches and yellow crookneck when 4-7 inches. Google your specific variety to determine the ideal harvesting size. Or harvest baby fruit. Why pay for gourmet vegetables when you can pick them in your own garden?!

Summer squash is low in calories and can be a source of Vitamin A and potassium. For some uses of summer squash, including a recipe for zucchini pickles, see Overrun with Zucchinis. And, don’t forget your neighbors on August 8th.