How to Keep Cilantro From Bolting (and What to Do When It Does)

How to Keep Cilantro From Bolting

You cannot stop cilantro from bolting, but you can delay it and plan around it. Sow seed directly in the garden in early spring and again in late summer, when days are cool and short. Make a new small sowing every 2 to 3 weeks. In warm weather give the plants light afternoon shade, mulch the soil, and keep them watered. Start cutting when plants are 4 to 6 inches tall, pinch off any flower stems, and choose a slow-bolting variety such as ‘Calypso’ or ‘Santo’.

Those six habits will not produce one plant that lasts all summer. What they give you is a row of young plants always coming along behind the ones that are finishing.

Why Cilantro Bolts

Cilantro is a cool-season annual, and flowering is the end of its life cycle, so every plant bolts eventually. Two signals speed it up: heat and long days. Oregon State University Extension describes the difference by season. In the cooler, shorter days of spring or fall, plants grow leaves for several weeks or months before flowering. In midsummer, a planting typically bolts into small white flowers and produces seed within four to six weeks.

Dry soil adds to the pressure. The Royal Horticultural Society notes that plants tend to bolt in hot, dry weather, at which point they put their energy into flowering and setting seed instead of leaves.

You can see it coming. The broad lower leaves give way to finer, feathery ones on a stem that lengthens from the center, and a plant that was a low rosette heads toward its full height of about 2 feet. Leaf production drops off from there.

When to Sow So It Bolts Later

Timing does more than any other step. Oregon State’s advice is to plant in early spring and again in late summer as temperatures cool and day length shortens. Seed germinates at soil temperatures of 55 to 68 degrees F, and mature plants tolerate light freezing, so there is no reason to wait for warm weather. A sowing that goes in late, on the edge of summer, will be the one that bolts within weeks.

Climate changes the calendar. Utah State University Extension splits its advice in two: in cooler locations, plant in early spring for a summer to fall harvest, and in warmer areas, plant in the fall and harvest in the spring. If your summers are long and hot, treat cilantro as a fall and winter herb.

Sow the seed where the plants will grow. Cilantro has a long taproot and does not transplant well, a point both the Wisconsin and Illinois extension services make. Direct sowing avoids that root disturbance. The details:

Step	What extension sources recommend
Depth	1/4 to 1/2 inch
Rows	About a foot apart
Thinning for leaves	3 to 6 inches apart
Germination	About 21 days
First leaf harvest	45 to 80 days from sowing; ‘Leisure’ in 28 to 40 days

Succession Sow Every 2 to 3 Weeks

Because each sowing has a limited leafy period, the reliable way to have cilantro for months is to keep sowing it. The University of Wisconsin and the University of Maryland both recommend successive sowings at 2 to 3 week intervals. Illinois Extension stretches that to every 3 to 4 weeks. Either way the batch should be small, a short row or one pot, so that it is used up about when the next one is ready.

Count backward from the harvest figures above to see why the interval works. A sowing needs roughly 45 days before its first cutting. With a new row started every 2 to 3 weeks, there are two or three younger rows at different stages behind the one you are cutting, and losing the oldest to flowering costs you nothing.

In midsummer, sowings come and go fastest. Keep the succession going through that period only if you can offer a cooler spot, as described next. The same approach works for other quick cool-season crops; see succession planting lettuce for a steady harvest.

Shade, Mulch and Water in Warm Weather

Cilantro grows best in full sun in cool weather, and Wisconsin notes it will tolerate very light shade. Once the weather warms, shade becomes a tool. Maryland suggests growing it shaded by other plants or in a spot that receives light afternoon shade. Oregon State recommends a cool or semi-shaded location during the warm season when leaves are the goal, and the RHS advises a cooler spot shaded from midday sun. The east side of a row of tomatoes or pole beans does this without any extra structure.

Soil temperature and moisture are the other two levers. Utah State’s instruction for slowing bolting is short: plant early when it is cool, mulch the soil to keep it cool, and make sure the plant is well watered. In pots, the RHS says to check daily and water as needed to keep the mix just moist. Avoid the opposite error too, because coriander dislikes soggy soil.

Containers have one advantage here. A pot can be moved out of the afternoon sun when a hot week arrives, which a garden row cannot.

Harvest Early and Pinch Flower Stalks

Start cutting sooner than feels natural. Maryland’s guidance is to harvest plants when they are 6 inches high, or to pick leaves sparingly when plants are 4 to 6 inches tall. You can take individual leaves, or follow Wisconsin’s method and cut the whole plant as a bunch an inch above the ground.

When a central stalk starts to rise, pinch it out. Maryland notes that pinching off the flower stems will extend the harvesting of leaves. The gain is modest and temporary, so treat it as a signal to cut heavily from that plant and check that the next sowing is in. The same pinching logic applies to basil, covered in how to pinch basil to avoid bolting.

Slow-Bolt Cilantro Varieties

Variety choice widens the window, especially for spring sowings that run into early heat. The University of Wisconsin lists ‘Calypso’, ‘Cruiser’, ‘Leisure’, ‘Marino’ and ‘Slo Bolt’ as slower to bolt. Illinois Extension describes ‘Leisure’ as heat tolerant and slow to bolt, ‘Marino’ as high yielding and slow to bolt, and ‘Santo’ as slow bolting. The RHS gives its Award of Garden Merit to ‘Calypso’ and ‘Cruiser’ among others for leaf production.

None of these is bolt-proof. A slow-bolting variety sown into June heat will still flower, so it needs the same timing, shade and water described above.

What to Do With Cilantro That Has Bolted

A bolted plant is still useful, so there is no need to pull it at once. The flowers are very attractive to beneficial insects such as adult syrphid flies and parasitic wasps, which is a reason to leave a few plants standing near vegetables.

The seed is coriander. A seed crop needs a growing season of at least 100 days. When the flower heads turn brown, cut the plants, put them head down in a paper bag, and shake the bag once they have dried to release the seed. Cilantro also reseeds readily when plants are allowed to go to seed, so a patch left to drop seed will often supply volunteer seedlings for the next cool season.