Coriandrum sativum
One seed and two crops. Cilantro runs to seed quickly once the days lengthen, which is the plant doing what it means to do rather than failing. Sow a short row every couple of weeks for leaves, and let one row go all the way, because the seed is coriander.
Pollinated by insects — fruit sets only where bees and other pollinators reach the flowers. Only relevant if you are growing the seed crop. The flowers are self-fertile but open and shallow, and they are worked heavily by hoverflies, small wasps and solitary bees, which set the seed more reliably than wind or self-pollination alone. One more reason to let a row flower: a bed of cilantro in bloom is one of the better sources of the predators that deal with aphids elsewhere in the garden.
Full sun in spring and autumn, and afternoon shade once summer arrives — shade will not stop it running to seed but it buys you another week or two of leaves.
Keep the soil evenly damp. Letting it dry out brings on flowering, and once cilantro flowers the leaves are finished.
Ordinary garden soil, loosened deeper than you would think for a herb. Cilantro puts down a taproot and resents being moved.
Compost dug in before sowing and one light feed part way through. Cilantro does not want to be pushed.
Nothing to tie up or train. The only handling this crop needs is a decision about flowering: pinch the stems out to keep the leaves coming, or let it run and take the seed.
Start cutting when the plants are about 150 mm tall. Take the outer leaves and leave the middle, or cut the whole plant 25 mm above the soil and let it come again once.
Coriander seed
Ready 70–100 days from sowing
30–45 days after flowering
Seed heads gone from green to tan or pale brown, with the whole plant drying off — Utah State and Illinois both use the browning of the heads as the signal · Seeds hard and round, rattling in the head when it is shaken · Cut before the heads shatter, because ripe coriander drops readily and you lose the crop to the soil in a windy day · A green seed is aromatic and usable fresh but will not store
Pick at 1/8 – 3/16 in (3–5 mm)
Harvest once — a terminal harvest
Keeps 730–1095 days — cool and dark
Cut whole plants once the heads have browned, hang them head down in paper bags somewhere warm and airy, and shake the seed out when everything is crisp — the method Utah State and Illinois both describe. Winnow the chaff off and dry the seed a further few days before sealing it, since seed stored even slightly damp goes musty. In a sealed jar out of the light it holds its flavour for two to three years, and it stays viable for sowing for about the same period. Grow the seed crop at a wider spacing than a leaf crop, thinned to 200 to 250 mm, since a plant carrying seed needs the room and the light. Worth saying plainly to anyone who has only bought it ground: whole seed toasted and crushed at the last minute is a different spice from the tin.
Slow. Cilantro can take three weeks to come up, so do not give up on a row and resow over it.
Thin the row while the seedlings are small — crowded cilantro is thin, weak and quick to run to seed.
The leaf window, and it is short. Broad rounded leaves now; when the leaves start looking feathery the plant is getting ready to flower.
Cut from about four weeks on. Take the outer leaves, or cut the whole plant 25 mm above the soil and get one more cut from it.
Flat heads of small white flowers. The leaf crop is over now, and the seed crop has just started.
The heads turn from green to tan and the seed hardens. Cut the plants before the seed starts dropping.
Slow-bolting leaf
Bred to hold in leaf longer before running to seed. Illinois names Leisure and Marino. The right choice for any sowing that will meet warm weather.
Seed type (coriander)
Grown for the seed rather than the leaf, at wide spacing. Santo is the usual dual-purpose choice; any variety will set seed if you let it.
Pot and windowsill
Compact types bred for container growing, such as Pot Cilantro 99057. Shorter and denser, and easier to keep in reach of a kitchen.
Stages affected: Seedling · Vegetative · Flowering
Small wedge-shaped sap-sucking insects that hop or fly sideways off a leaf the moment you disturb it. The feeding damage on its own is minor on most garden crops. They matter because one of them, the aster leafhopper, carries the phytoplasma that causes aster yellows, and once a leafhopper has picked that up it spreads it for the rest of its life. On carrot, celery, lettuce and the whole carrot family, the insect is a nuisance and the disease it carries is not.
Stages affected: Vegetative · Flowering
Not a disease and not a mistake: the plant switching from making leaves to making seed, which is what it was always going to do. It matters because in a leaf or root crop the switch ends the harvest — the plant pours everything into a flower stem, the leaves turn narrow and bitter, and a root goes woody. Lengthening days, heat and any check to growth all bring it forward, and which of those dominates depends on the crop. Cilantro and spinach are driven mainly by day length, lettuce and radish mainly by heat; biennials such as parsley and celery bolt after a spell of cold followed by warmth, so an overwintered plant runs to seed in spring. A dry spell or a transplant check will trigger any of them. Once a plant has committed there is no way back, so everything useful happens before it starts.
Stages affected: Germination · Seedling
The name covers several different soil organisms doing the same thing: killing seedlings at or just below the soil line, either before they emerge or in the first fortnight after. Most of the damage in cold wet conditions comes from Pythium and Phytophthora, which are oomycetes rather than true fungi, but Rhizoctonia and Fusarium do the same job in warmer soil. The organisms are present in almost every garden soil and most reused potting mix; what turns them from harmless to lethal is cold, wet, airless conditions and a seedling that takes too long to get up. Utah State names it as one of the three problems on cilantro, which is a slow germinator sown into cool spring soil.
Stages affected: Seedling · Vegetative · Flowering
Small soft-bodied sap-sucking insects that cluster on the softest new growth. They reproduce extremely fast in warm weather and are the main insect vector of plant viruses in the garden.
Stages affected: Germination · Seedling
Soft-bodied molluscs that feed at night and in wet weather, rasping holes in leaves. Seedlings and low soft foliage are the most at risk, and a single night can take out a row of young plants.
Stages affected: Vegetative · Flowering
Not a fungus and not quite a bacterium: a phytoplasma, a wall-less organism that lives in the plant sap and is injected by a feeding leafhopper. It cannot be cured, it does not spread from plant to plant by touch or splash, and an affected plant never recovers. Utah State lists carrot, celery, lettuce and wheat among its hosts and the range is far wider, taking in most of the carrot family and many ornamentals. The characteristic result is not rot or spotting but distortion: growth that comes out yellow, narrow, oddly upright and multiplied into a broom of small shoots.