What I am about to write comes with a major disclaimer. Summer squash is one of the easiest and most productive vegetables that can be grown in a garden. The seeds are big, they germinate in less than a week, they grow fast and as long as plants are healthy, they will keep producing for weeks. The disclaimer, if you haven’t already guessed, is this: as long as your plants are not attacked by the squash-vine borer, the vile spawn of an innocent-looking and rather attractive orange-and-black moth. The adult moth flutters around squash plants until she finds the perfect spot along the stem or under a leaf to deposit a single round, brown egg, not much larger than a pinhead. Then she looks for another perfect spot — that may or may not be in the vicinity of the first egg or even on the same plant — and lays another. And another. And she or a relative might come back the next day and lay some more, one single egg at a time.
Each egg hatches into a creamy white borer that is so tiny you’ll hardly notice until it has eaten its way into the stem, leaving a pile of sawdust-like frass at the entry site. Protected from the elements and hidden from sight, it grows into a bulging larval progeny, devouring the inside of the stem and disrupting the flow of water and nutrients, causing the leaves to reach a point of wilting, from which they cannot recover. Ultimately the plant declines into a sad, droopy heap of yellowing leaves, while the squirming larva exits the stem, pupates in the soil and emerges the following year as a moth in search of a mate and — you guessed it — squash plants. And the cycle begins again. Countless gardeners share my frustration with the squash-vine borer, and many have even abandoned growing squash altogether. However, if you have been afflicted by this pest, you don’t have to give up on homegrown squash. I beat it and you can too, but first let’s take a closer look at this quintessential summertime crop.
Summer squash (Cucurbita pepo) is an all-encompassing category that includes crookneck, zucchini, pattypan and globe varieties that develop on bushy plants with large lobed leaves held high on sturdy stems. Unlike winter squash that takes upwards of three months to mature fully on the vine, summer squash is harvested at an immature stage, before it has a chance to develop hard seeds and a tough skin. Most varieties grow from seedling to flower in 40–50 days with squash reaching harvestable size less than two weeks later. There are hundreds of cultivars available to home gardeners, in shades of vibrant green, sunny yellow and creamy white. Some are two-toned, some have striations or ridges, some have bumps and some are smooth and perfectly round. I love their diversity in the garden and their versatility in the kitchen. And they are a snap to prepare; the mild flavor of summer squash mingles nicely with other vegetables, grains, herbs and flavorings, whether shredded, sautéed, grilled, roasted, fried or spiralized. And no peeling or seeding is necessary. The following list represents a small sampling of the diverse varieties available to home gardeners.
‘Benning’s Green Tint’. A scalloped, pale-green heirloom that has been grown in this country since the early 1900s. Prolific plants yield fruit that is best when harvested small, only 3–4 inches across. Prized for outstanding flavor and tender flesh; very attractive when sliced lengthwise or crosswise.
‘Bossa Nova’. An All-America Selections winner from 2015, this pretty, pale green zucchini has dark-green mottling and mild, succulent flesh. And best of all, it is an early producer, about 10 days earlier than most varieties.
‘Costata Romanesco’. A traditional heirloom from Italy, this green zucchini yields cylindrical fruit with prominent ribbing. Favored for its dense, flavorful flesh and edible yellow blossoms.
‘Partenon’. A classic, dark-green zucchini that is parthenocarpic (it does not require bees for pollination); a big plus if you are growing squash under cover to protect from pests.
‘Sunburst’. Use your imagination when preparing this golden-yellow pattypan, an All-America Selections winner from 1985. Miniature, whole squash can be grilled, roasted or stir-fried; slightly larger squash can be scooped out and stuffed for an attractive side.
‘Tromboncino’ (60–70 days). A favorite! Belonging to the squash species Cucurbita moschata, this Italian heirloom also goes by the names zucchino or zucchetta rampicante, trombetta and tromba d’Albenga. It is an amazing dual-purpose squash that can be harvested as an immature zucchini or can be allowed to mature into a tan, long-necked winter squash with a hard skin that keeps for several weeks. To eat as a summer squash, harvest the fruit when it is pale-green and tender, between 12 and 18 inches long. It has a firmer texture than standard zucchini, and I once heard its flavor described as walnuts combined with pumpkin and a touch of artichoke. Squash in the C. moschata group are considered more resistant to squash-vine borer. However, in my experience the borer still gets in the stems of ‘Tromboncino’, but the vines quickly outgrow it by setting down more roots. This variety is a vigorous vining plant; so give it a fence or sturdy trellis to grow on. And if you like squash blossoms, this may be just the squash for you — they are big, beautiful and plentiful.
‘Zephyr’. A flush of pale-green coloring at the blossom end gives this summer crookneck an attractive appearance. A unique squash with firm flesh and a delicate flavor. Developed by the research team at Johnny’s Selected Seeds, it was bred for taste, quality and adaptability.
A SQUASH IS BORN
It helps to understand how squash is “born.” Squash is monoecious, bearing a profusion of both male and female flowers on the same plant. Male flowers develop on a long slender stem, and the tip of each male flower contains the anthers that produce the pollen. At the base of a female flower there is a miniature fruit, called the ovary, filled with immature seeds, called ovules. Most squash is dependent on bees and other pollinators to transfer the pollen grains from the male anthers to the stigma of the female flower in order to fertilize the ovules, which will become the seeds that will pass on the genetic information — the plant’s ultimate goal. If the pollination process is incomplete or disrupted, the miniature fruit will gradually shrivel. However, if fertilization is successful, the tiny squash will start to develop, the flower will wither and fall off, and squash harvest will follow. It’s an amazingly complex yet seemingly haphazard process that makes growing vegetables all the more fascinating. To add another layer of complexity, it is a common occurrence for male flowers to bloom without a female blossom in sight, but that’s OK; the female blooms will generally show up a week or so later as the plant continues to produce male flowers.
Excessive rain, hot weather and lack of pollinators can all interfere with pollination. We don’t have any control over rain and heat, but if bee activity is low, gardeners can help their plants along with hand-pollination. Mimic a bee by using a paintbrush to collect the yellow pollen from the stamens of the male flower and dab it lightly onto the stigma of the female flower. Make sure you can actually see yellow pollen grains or else it may mean that the anthers are not ripe or possibly past their prime. Alternatively, cut a male flower, peel back the petals and gently rub it over the surface of the female stigma to transfer the pollen grains. It’s best to do this in the morning when the flowers are open and receptive to pollination.
BEAT THE BORER
As previously mentioned, squash-vine borer is the nemesis of squash, leaving the novice gardener bewildered and the veteran gardener fuming. Once it burrows into a stem and destroys the interior plumbing, the plant’s demise is imminent. Over the years I have dusted my plants with Bt, wrapped the stems with foil, planted oregano among my squash, clobbered the moth with a fly swatter, injected Bt into the stem, surgically removed the borers and combed every squash plant to pick off tiny brown eggs and still I have lost many plants to squash-vine borer damage. Most of these methods have worked to some extent, but the challenge is keeping up during a busy gardening season — it’s a lot of work! As long as the moth is active, you cannot let up or else the borer will win. Unfortunately, the moths emerge from the soil in the spring and can remain active into fall. That means constant checking for eggs, reapplying Bt, probing of stems, squishing of larvae — you get the picture.
Ultimately, the most effective and least labor-intensive method of preventing borer damage is to prevent the moth from laying her eggs in the first place. This can be easily accomplished by covering the plants with a lightweight insect barrier. The last few years I have been using Micromesh on my squash and I prefer it over the standard floating row cover that has been recommended for so many years. Micromesh is a fine-gauge mesh netting that protects plants from damaging insects and allows water and light to pass, but it is more see-through and more durable (less prone to tearing) than standard row cover. It helps exclude other squash pests as well, such as squash bugs, aphids and whiteflies, and also provides better ventilation, an important factor as the warm season progresses. I like that I can peer through the netting to check on my plants and don’t have to lift it up every time, as I do with opaque row cover.
Micromesh can be purchased at Amazon (www.amazon.com), Territorial Seed (www.territorialseed.com) and Harris Seeds (www.harrisseeds.com), and is also available at some garden centers. Purchase it before you even plant your first squash seed because you will need it right away.
As soon as squash seedlings emerge, drape the Micromesh over wire hoops or a frame made from PVC pipes and seal the edges of the mesh with soil, sandbags, bricks or u-pins so the moth cannot get under it. Leave it in place until the plants begin to produce female flowers, then remove the cover so the blossoms are exposed for pollination. This will, of course, subject plants to the risk of the squash-vine borer, but at this point the plants are several weeks old and primed to start pumping out edible squash before any borers have enough time to inflict fatal damage. Some gardeners prefer to leave the cover on for the life of the squash, opting to hand-pollinate on a regular basis, but again, this takes time away from other tasks during the garden season, especially if you have several plants that need pollinating. I’ve had such good results with Micromesh that I am happy to take my chances by removing it at the appropriate time and letting the pollinators take over.
The quick growth of summer squash and the mild fall weather in Texas mean we can grow both a spring and fall crop. Some years, a fall planting may turn out to be more successful than a spring planting, as autumn heat and insect pressure diminishes. Last fall I planted seed of four squash varieties in August, covered them until the female flowers appeared, and like clockwork, I was harvesting a satisfying bounty in October. It should be noted that if you had a squash-vine borer infestation, then you likely have pupae (mahogany-brown cocoons about 1/2 inch long) in that same area about two-to-three inches below the soil waiting to emerge in spring. If possible, rotate squash plantings to a different planting bed each season, discard infested vines and turn the soil during the winter to expose the pupae. And always monitor plants, even if they are covered. Insects have a vexing way of sneaking in.
By Patty G. Leander, B.S.
Advanced Master Gardener — Vegetables