Cucumber

Direct sow only after the soil hits 65-70F

Wait until soil at one inch deep reads 65-70F, then sow seeds an inch deep, 12-18 inches apart in rows about 4 feet apart. Black plastic mulch warms the soil and lets you start earlier; hold off on organic mulch until the soil is above 75F. Cucumber seed germinates between 65 and 85F and rots in cold wet ground, so seed sown into soil that has not warmed simply disappears rather than emerging.

Set out transplants after frost, roots undisturbed

Start seed indoors no earlier than four weeks before your last frost date and use peat pots that go into the ground intact. Move plants out once frost danger has passed, transplanting carefully before the plant outgrows its container so the taproot is not damaged. Cucumbers resent root disturbance because of their taproot, and seedlings held indoors too long transplant poorly and stall.

One to two inches a week, delivered at the ground

Give 1-2 inches of water per week depending on plant size, deeply rather than in daily sips, using drip line or a soaker hose so the leaves stay dry. Inconsistent moisture is what makes cucumbers bitter and misshapen, and overhead water sitting on foliage is the film that downy mildew and angular leaf spot need to infect.

Sidedress nitrogen once the vines start to run

When the plants put out runners and before the first flowers open, sidedress 3-4 tablespoons of a nitrogen fertilizer such as 21-0-0 per plant, scattered beside the row rather than against the stem, then water it in. Cucumbers build their whole fruiting frame in a few weeks of vine growth, and the nitrogen that carries that expansion has to be in place before flowering starts, not after fruit is already sizing.

Check seedlings for cucumber beetles two to three times a week

From emergence through the third true leaf, look on stems, leaf undersides and at the base of each plant. The action threshold is two or more beetles per plant on a quarter of your plants at the cotyledon stage, or a quarter of a plant defoliated at the first to third true-leaf stage. Beetles that show up later in summer on established vines can be ignored. The beetles carry Erwinia tracheiphila in their gut and their feces, and it enters through fresh feeding wounds in rain or dew, so a few beetles on a seedling are a wilt infection rather than just chewed leaves. Plants are most vulnerable between emergence and bloom.

Spinosad on seedlings if beetles pass threshold before bloom

Only if scouting hits the threshold on pre-bloom seedlings, spray spinosad, directing it at the stem base and leaf undersides where the beetles hide rather than just over the canopy. Stop treating once flowering starts. Killing the vector during the cotyledon-to-third-leaf window is what actually prevents bacterial wilt, because once the bacterium is in the xylem the vine is unsavable and dies in a couple of weeks.

⚠ Spinosad carries a 3 day pre-harvest interval on cucurbits - do not harvest within 3 days of spraying. Do not spray once blossoms are open: spinosad is toxic to bees while wet, and cucumbers depend on insect pollination to set fruit. If beetles are present at bloom, use row covers or hand-removal instead, not an insecticide.

Chlorothalonil for downy mildew once it is reported nearby

Watch for yellow areas on the upper leaf surface that turn brown with irregular margins, with a gray mold on the underside. Fungicides only work preventatively, before symptoms appear, so if downy mildew is active in or near your garden, apply chlorothalonil and cover the leaf undersides. Downy mildew moves fast in cool humid weather and can strip a planting once it arrives. Resistant and tolerant varieties (Marketmore 76, Diva, Dasher II, Calypso) slow it down but modern strains have eroded that resistance, so tolerance reduces losses rather than preventing infection outright.

⚠ Chlorothalonil carries a 0 day pre-harvest interval on cucurbits. It is a fungicide, not an insecticide, but still avoid spraying open blossoms when bees are foraging.

Pull the row covers the day the first flowers open

Row covers laid over the bed at seeding or transplanting exclude striped cucumber beetles through the vulnerable seedling weeks, but take them off as soon as flowering begins unless you are growing a seedless parthenocarpic variety. Cucumbers need insect pollination to set fruit, and a cover left on past first bloom locks the bees out - you trade beetle damage for no crop at all.

Pick every day or two, and never off a wet vine

Fruit is ready 5-7 days after flowering. Pick young and tender at your variety's size rather than letting fruit fill out, and keep picking on a one to two day cycle. Do not pick fruit while the vines are wet, because of the danger of spreading diseases. A cucumber left to mature on the vine signals the plant to stop setting fruit, and flavor drops as the seeds harden and the skin toughens. Handling wet vines spreads bacterial and fungal disease from plant to plant.