What's Cilantro? How to Cut It Before It Bolts

Yes, and the difference is timing rather than species.

Coriandrum sativum is one annual that yields two things people buy under two names.

Wisconsin Horticulture places it in the carrot and parsley family, Apiaceae, which puts it beside carrot, dill and parsley in the bed and in the way it behaves.

NC State separates the two harvests by part.

The leaves and stems are used to flavor dishes, and those are what a shop sells as cilantro.

The mature seeds are called coriander and are used for flavoring in their own right.

The plant changes shape between the two.

Wisconsin gives it as 12 to 18 inches high in leaf, with flower stems reaching 2 to 3 feet once it runs. The extra height is the seed crop starting.

A flowering plant is the start of the coriander crop.

Whether that is useful depends entirely on which of the two you were growing for, and the spacing and harvest figures below treat them as two different crops.

Heat ends the leaf crop.

NC State says the plant bolts easily in hotter climates and grows best in cool climates in spring and fall.

Illinois puts the trigger in plainer terms, saying it bolts when it gets really hot.

Utah State gives the one number worth working to. Keep the soil temperature below 75°F, which is a more useful target than air temperature because soil holds its heat and a bed in full sun runs warmer than the thermometer on a shaded wall suggests.

There is a visible warning before the stalk appears.

Wisconsin describes the wide, flat lower leaves giving way to lacy, fern-like leaves along the flower stalk, and that change in leaf shape starts before the plant is obviously running.

A plant whose newest leaves have gone feathery has already made the decision.

Nothing reverses it once the stalk is up. None of the sources gives a way to turn a bolting plant back into a leaf plant, so from that point the choices are to cut the remaining flat leaves or leave the plant for seed.

At the other end of the year the limit is simpler. Wisconsin says cilantro will not survive a hard freeze, so the fall crop ends on a date rather than on a temperature trend.

Sow it where it will grow.

Wisconsin says cilantro does not transplant well because of its long taproot, which is the same reason dill has to be direct-sown.

A plug tray is the wrong start for both, and the choice between sowing direct and raising transplants is made for you here.

Depth is uncontroversial. Wisconsin puts the seed a quarter to half an inch deep, and Utah State gives half an inch, so anywhere in that band is right.

Spacing is where the two crops part company. Utah State spaces plants 2 inches apart for a leaf crop and 8 to 10 inches apart for a seed crop, with rows at least 15 inches apart in the second case.

The reason for the gap is what each crop asks of the plant.

A leaf crop is cut young and small, so crowding costs nothing and a dense row gives more leaf per square foot.

A seed crop has to carry a plant to 2 or 3 feet with a branching head on it, and that needs room.

A row sown at 2 inches and then left for seed holds its plants far closer than the 8 to 10 inches Utah State gives, so the plants compete for the room a seed head needs.

Deciding which crop a row is for before the seed goes in is the whole of the planning here.

If seedlings have to be raised under cover, Utah State says to start them 4 to 6 weeks before transplanting and to minimize root disturbance when moving them. Utah State treats that as the fallback, and the taproot is the reason.

The answer every source gives is an interval, and they do not quite agree on it.

Wisconsin recommends successive sowings at 2 to 3 week intervals and Illinois gives 3 to 4 weeks. Either turns one crop that ends into a series that overlaps, and the shorter interval buys more overlap in a hot summer.

Variety choice buys time on top of the schedule. Illinois names Leaf, Long-Standing, Slo-Bolt, Calypso and Santos as the ones recommended for delaying bolting and staying vegetative longer.

The two work together rather than as alternatives. A slow-bolt variety sown every three weeks gives a longer season than either the variety or the schedule manages alone.

It also pays to sow less each time than instinct suggests. A short row every two weeks beats a long row every six weeks, because the long row bolts as one and the kitchen cannot use it in the window it has.

Basil, grown beside it, wants the opposite weather entirely and does not need this treatment.

NC State gives a wide light range. It lists full sun of six or more hours, or partial shade of two to six.

Utah State describes the soil simply, saying cilantro grows well in most soil types provided they are well drained and moderately fertile.

Illinois says to keep cilantro in a shadier, cooler location during the heat of summer, which is unusual advice for a plant listed as taking full sun and follows directly from the bolting problem. The shade is there to keep the soil below Utah State's 75°F figure.

Fertility is a light touch rather than a feeding program. Utah State asks for 2 to 4 inches of well-composted organic matter worked in per 25 square feet before sowing, then very little afterwards.

Watering changes as the plant establishes. Utah State says cilantro needs regular watering during establishment and little water once established, and warns against over-watering because the plant does not do well in damp or humid conditions.

That last point matters in a summer bed. A plant that is being watered heavily to keep it cool is being given the one condition it dislikes, and shade does the cooling job without the damp.

The leaf harvest starts earlier than most people wait for.

Utah State cuts leaves when they are about 4 to 6 inches tall, and Wisconsin picks any time after the plants are about 6 inches tall but before they bolt.

Small and early is the whole strategy on a plant with this short a window.

The seed harvest is judged by color rather than by date. Wisconsin says to harvest the seeds when they turn a light brown, which comes 2 to 3 weeks after flowering, and Utah State cuts the heads once plants begin to turn brown.

The paper bag does real work. Ripe coriander sheds where it is cut, so heads carried loose to a bench leave most of the crop in the path, and a closed bag catches everything as the heads finish drying.

In practice the two harvests come off different plants. The early sowings are cut for leaf and pulled, and one or two later plants are left to run, which is also what supplies seed for the next year if you want it.

There is, and it has nothing to do with the kitchen. Wisconsin describes the flowers as little white or pale pink blooms borne in umbels, which is the flat open head shape the whole carrot family shares.

That shape is the point.

Wisconsin says the flowers are very attractive to small beneficial insects such as adult syrphid flies and parasitic wasps, which consume the nectar. Both are insects whose larvae work on garden pests, and both are too small to feed from a deep flower.

A bolted plant left standing is doing something a leafy one cannot. It is worth leaving one or two at the end of a row for that reason alone, alongside the other plants grown to bring predators in and the rest of a beneficial insect planting, and the same plant is making next year's coriander while it does it.

Wisconsin gives an unusually short answer, saying cilantro does not have any serious pest problems, and noting only that some commercial growers have reported problems with a bacterial leaf spot. For a soft-leaved annual in a vegetable bed that is a good record.

Penn State Extension gives the fuller list. Aphids are the most common, gathering on the undersides of leaves and along the stems, and a forceful spray of water removes most of them.

Leafhoppers are worth naming separately. Utah State lists them alongside aster yellows, a disease they carry, in which flowers turn yellow and the plant grows tall and spindly before it becomes sterile. The control Utah State gives is aimed at the leafhoppers rather than the disease.

Bacterial leaf spot has its own handling. Penn State says to remove diseased plants immediately rather than composting them, water at soil level, and avoid sowing where parsley, celery, chervil or dill grew before.

Cilantro is listed as non-toxic to dogs, cats and horses by the ASPCA, which files it under Coriandrum sativum with coriander, Chinese parsley and dhania as other names. NC State's toolbox tags the species non-toxic for the same three animals.

That record covers the plant. It does not cover concentrated coriander oil, and it says nothing about leaves sprayed with a pesticide. The carrot family is no guide either, since the ASPCA lists parsley, in the same family, as toxic to all three animals, which matters when a full kitchen bench goes in where an animal grazes.