how to grow squash, cucumbers and other cucurbits, with tom stearns

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WITHOUT THEM, there would be no proper pickles, no pumpkin pies, no ratatouille. The melon-baller would sit idle, summer fruit salads undermined. Cucurbits are favorite food plants—but can be challenging. Don’t give up; learn how to grow squash, melons and cucumbers, with Tom Stearns.

Squash pests and diseases—from squash bugs, vine borers and cucumber beetles, to powdery and downy mildews and bacterial wilts—can make it all sound like just too much. But as a seed farmer, High Mowing Organic Seeds founder Stearns has to harvest lots of extra-ripe fruit to get his hidden-inside crop. He gets to the finish line by working to avoid any preventable setbacks, first and foremost, always keeping in mind the three key things about being a cucurbit:

You love heat.
You’re thirsty (but your shallow root system means you depend on the immediate area for water resources).
You love to eat.

Oh, and the aforementioned “issues” love you—some more or less depending on species and variety, or what region you garden in, or both.

step 1: provide enough consistent heat

ESPECIALLY in the early growth stages, says Tom (who farms in Zone 4B northern Vermont), never let a cucurbit cool off.

“If you put a seed in cold soil,” he says, “it will take three times the normal time to germinate—and it will come out of ground so weak and susceptible to disease and other issues.” Ideal soil temperature for cucumber and summer squash germination, for instance: 85F (with no sprouting below 60F).

Likewise, even if you start seeds in the cozy indoors on a heat mat and grow them under lights, but then transplant into cold garden soil, “the seedlings will just sit there.”

“Big reminder: heat,” says Tom.

Recommendations: Pre-warm the soil with black plastic sheeting for a week before the setout date (which is just after final frost). Transplant most cucurbits into slits cut in the sheeting after a headstart of 3-4 weeks indoors; watermelons at 6 weeks. (That’s a black plastic-covered squash row at High Mowing after harvest, above.) Many gardeners also cover cucurbit transplants with Reemay for extra warmth; more advice on that under “more pest protection,” below.

step 2: provide ample needed fertility

CUCURBITS are really heavy feeders. “You can’t really overfertilize,” Tom says, “the way you can with tomatoes and peppers, where you’d get only foliage by adding too much Nitrogen, at the expense of fruit set.” (Tom is an organic farmer, so he’s not talking about the potential for overdosing crops with fast-acting chemical Nitrogen, which can “overfertilize” or even destroy plants.)

“These are primarily vegetative plants,” says Tom. “Producing 10- or 20-foot-long vines compared to the amount of fruit per vine requires lots of fertility.”

Cucurbits are not too particular about micronutrients, he says. “I think of Nitrogen as the one they want if struggling. That’s tricky, because if the only source you used was quick acting–like foliar feeds of kelp or fish emulsions–a rainy summer can wash it down to depths that cucurbits can’t tap into.” If that happens, make another application of quick-acting foliar sprays, but remember: Compost and high-organic-matter soil help longer-term by making N steadily available to replace what may have leached. Don’t skimp on proper soil-building and top-dressing.

Recommendations: Cucurbits want a high-organic-matter soil. Topdress before laying down plastic with compost and/or organic fertilizer such as blood meal or alfalfa meal, then tuck a little more into planting holes. An extra benefit to soil-warming, weed-suppressing plastic: It limits nutrient leaching from rain.

Rotating where cucurbits are planted may help outsmart pests (though admittedly, rotation works better in a large-scale setting than small gardens). Rotation can also help provide for enhanced fertility. “We work hard to have the rotation for squash be in a good position–following a crop that’s putting down Nitrogen in the right form, such as after a pea cover crop,” says Tom.

step 3: water regularly, or else

EVER LOOK at the root system of a spent cucurbit plant while pulling them at cleanup time? Not much to speak of, relatively.

“Cucurbits can’t tap into resources that are much deeper than 6 inches,” says Tom. No wonder if the plant dries out it’s very stressful—another preventable potential setback.

Recommendation: Provide regular, thorough watering throughout the root zone, without waterlogging the soil.

backing up: start with the right cucurbit variety

CHOOSING THE PROPER SEED is your first defense. Select a variety described as a good performer in your region. Seek out varieties that are bred for, or noted to have, superior resistance to pests and disease. With melons, says Tom, powdery mildew resistance is very important, for example, because the disease can really suck the sugar out of the fruit. (Melon growing, step by step.)

Also look for word in variety descriptions of exceptional vigor—since a wimpy plant that technically survives disease by just sitting there but with little fruit isn’t much help.

“Lately I’ve been paying attention to the vigor in different varieties—the plant’s adaptability and ability to handle lots of different conditions, to be resilient,” says Tom. “Sometimes when you breed for high disease resistance, if you’re not paying attention it won’t be very vigorous and produce much. If it’s really vigorous, however, it may outgrow the mildew and keep producing.”

Know the enemy’s preferences: For example, cucumber beetles love Cucurbita pepo varieties (including summer squashes, traditional pumpkins, and acorn types) and also C. maxima varieties (including many popular winter squash, such as buttercups, hubbards, turbans, kabochas, bananas)—but not butternut types (C. moschata, above) so much. Butternuts are also generally resistant to squash bugs, as are some others; again: read descriptions when buying seed.

Insights on insect preferences (such as for C. maxima) can also be used strategically on farms and in bigger gardens to plant a “trap crop” to lure pests to, perhaps sparing your main crop.

Short-season varieties may help you beat the problem clock. A must up North, short-season varieties can help Southern gardeners, too. Even where diminishing late-summer heat isn’t an issue, the shorter days-to-harvest means harvesting before mildew sets in, or before drought conditions weaken plants.

Recommendations: Select regionally appropriate, resistant, and perhaps short-season varieties where possible–and scan variety descriptions for hints about vigor, too.

more pest protection

REMEMBER that a weak plant is a vulnerable plant; work to avoid any of the potential stressors explained above (too little warmth, water, or fertility).

Many gardeners cover all their cucurbits. With all melons in particular (and butternuts, to add heat), Tom says, cover with Reemay at transplant time, opening the tunnels or removing the fabric a week to 10 days after the first flowers appear, to allow for insect pollination. Reemay should be buried on the bed edges for complete control.

Seedlings at High Mowing that are not going to be covered are dunked in or sprayed with a kaolin clay solution before setout, to deter striped cucumber beetles. (One brand-name product is Surround.) Some transplants get both clay and a heat-increasing cover.

Planting successions of summer squash gives continuous harvest, and one generation may fare better against timing of pest or disease outbreaks. Transplant the first succession immediately after your frost-free day, with the final succession three months before predicted first frost. “It’s better to plant a couple of cucumber or summer squash plants every couple of weeks,” says Tom, “rather than depend on one planting.”

Prompt cleanup of vines and roots as fruit production declines is essential. Squash bugs (above), for instance, can even overwinter as adults; leaving debris in place longer than necessary invites a population explosion. (This new companion story with entomologist Diane Alston gives more detail on squash bugs and other pests.)

Recommendations: Mechanical barriers can help thwart pests organically, as can succession plantings and prompt garden cleanup.

some of tom stearns’s favorite squash and cukes

Summer squash: ‘Dark Star’ (a new Organic Seed Alliance collaboration), for its vigor; ‘Dunja,’ from a breeder in Holland, which is both highly resistant and high yielding; for grilling, Lebanese types (with paler skin, and fatter at the bottom) like ‘Segev;’ ‘and ‘Costata Romanesco’ and ‘Cocozelle’ for great flavor.
Cucumbers: Open-pollinated ‘Green Finger’ from Cornell breeding has a deservedly huge following, Tom says. Small-fruited ‘Picolino’ (below, meant to be picked as small as 3 or 4 inches, or as big as 5) and ‘Manny’ (below) are lunchbox-sized favorites for kids and adults, too.

enter to win the cucurbit seeds

I’VE PURCHASED three sets of four cucurbit varieties each from High Mowing–‘Dunja’ F1 summer squash and ‘Picolino’ F1 cucumber and ‘Nutterbutter’ winter squash and ‘PMR Delicious 51’ melon–for three giveaway winners to try in their 2015 gardens. [UPDATE: The giveaway is now over. Your comments are always welcome, though.]

All you have to do to enter: Answer this question in the comments box at the bottom of the page, scrolling all the way down, after the last reader comment:

With cucurbits, what’s your hit, and your miss–the one you do best with, and then one that challenges you most, and why? (It’s fine if you report that you never fail, or totally fail, with all of them–just let us know, and tell us where your garden is, too. Favorite varieties, worst pests and diseases; let us know.)

(My answer: I always do well with Butternut-type squash in Zone 5B in the Hudson Valley of New York, but some years the longest-season C. maxima types don’t reach the finish line. I hand-pick insects and eggs vigilantly, grow all my cucurbits on black plastic, and do keep up with watering, too.)

No answer, or feeling shy? You can also just say, “Count me in” or something like that, and I will–but I’d love to learn more about your garden experiences.

Three winners will be were chosen at random after entries closed at midnight Sunday, March 22, and informed by email. U.S. only.