Tomatillo

Start seed indoors four to five weeks before setting out

Sow a quarter inch deep in sterile soilless mix and hold the flat at 75F to 85F until seedlings emerge, then grow them on at about 70F. Start a week or two later than you would tomatoes, and harden the plants off over one to two weeks before they go out. Sow at least two plants, ideally of two different varieties. Tomatillo germinates on soil heat rather than air temperature, and the seedlings get leggy if started as early as tomatoes. Two plants is not a suggestion: tomatillo flowers will not set on their own pollen, so a lone plant husks up and stays empty.

Transplant once frost is past and soil is over 60F

Set plants out after all danger of frost has passed and the soil has warmed past 60F, spacing them 2 feet apart in rows 3 feet apart, or up to 3 feet apart if you are not caging them. Cage or stake at planting, and rotate the bed each year rather than replanting where tomatoes, peppers, potatoes or eggplant grew last season. Tomatillo has an indeterminate, sprawling habit and benefits from staking or caging to keep the fruit off the ground and improve air circulation through the plant. Utah State's guidance for holding disease down on this crop is simple rotation: move the crop placement in your garden every year rather than returning nightshades to the same ground.

One to one and a half inches a week, delivered at the ground

Give about 1 to 1.5 inches of water per week and keep the moisture even, never letting more than the top inch of soil dry out. Use drip or a soaker hose rather than overhead sprinklers, and water in the morning if you must wet the leaves. Tomatillo is more drought- and heat-tolerant than tomato thanks to a strong root system, but overhead sprinkling makes the plants more disease-prone. Flowers also drop above 90F and below 55F, and steady soil moisture buffers the plant through heat.

Side-dress lightly at four and eight weeks after transplanting

Side-dress about 1 tablespoon of 21-0-0 per plant at four weeks and again at eight weeks after transplanting, watering it in away from the stem. Apply phosphorus and potassium only to your soil test. Tomatillo answers extra nitrogen by making more plant. Over-fertilized plants go bushy and leafy and are slow to bear, so the goal is a light nudge, not a feeding.

Three-lined potato beetle: hand-pick from the first leaves on

Check leaf undersides for orange-yellow egg clusters and for larvae that carry their own excrement on their backs. Knock adults and larvae into soapy water and crush the egg clusters. Pull ground cherry and other nightshade weeds nearby. This beetle is a curiosity on most crops and a serious defoliator on tomatillo specifically, and the larvae do the real damage. Ground cherry is its alternate host, so a weedy edge keeps reseeding the problem.

⚠ No insecticide is well matched to this beetle and few labels even list it. Hand removal is the recommended control, and it avoids spraying a crop that is in bloom and depending on bees for nearly its whole season.

Hornworms: check twice a week and treat them small

Look for dark droppings and stripped stems at least twice a week, and hand-pick the caterpillars into soapy water. If there are too many to pick, spray Bacillus thuringiensis kurstaki and cover the leaf undersides, since the caterpillars must eat it. Leave any hornworm covered in white cocoons where it is. Bt only kills young caterpillars, so the twice-weekly check is what makes it work; a full-grown hornworm will shrug it off and defoliate a plant in a day. The white cocoons are braconid wasps that will emerge and hunt the next generation for you.

⚠ Bt kurstaki is specific to caterpillars and does not harm bees, which is why it is the right choice on a crop that is in bloom and bee-dependent all season. Follow the label rate and its pre-harvest interval.

Black plastic and row cover for an early start

Lay black plastic mulch about two weeks before your last frost to warm the soil, and float a row cover over young plants for faster early growth. Vent the cover whenever the air temperature inside it exceeds 80F. Take the cover off once the weather has stabilized, and in any case the moment the first flowers open. Warm soil is what a tomatillo is waiting on, and black plastic warms the soil, conserves water and helps control weeds. Once flowering starts the cover becomes a liability: Utah State is explicit that tomatillos are not self-fertile and need multiple plants for proper fruit set, and that pollen has to be carried between them.

⚠ Remove row covers at first bloom. Tomatillo cannot self-pollinate and depends on insects to cross-pollinate between plants, so a cover left on through bloom will cost you the crop.

Pick when the fruit fills and splits the husk, still green

Harvest once the fruit has completely filled the papery husk and the husk has dried, turned from green to tan and begun to split open, while the fruit itself is still green and firm. Ripe fruit comes off the plant easily — twist and pull gently, or snip it with scissors. Green varieties should be picked before they start to turn yellow or purple, and the plant is indeterminate, so keep picking through to frost. A tomatillo fills its husk before it colors, and the husk drying and splitting is the plant telling you the fruit is sized. Once the fruit turns yellow or purple the acidity that carries a salsa verde has faded and the flesh has gone soft.

⚠ Where the husk splits, the fruit is exposed to soil contamination from rain splash and from any fruit that drops. Peel and wash tomatillos before use.