Bolting cilantro changes shape. The broad, flat lower leaves that look like parsley give way to a taller central stem carrying fine, feathery, threadlike leaves, and small umbrella-shaped clusters of white or pale pink flowers follow. The feathery leaves are edible but sparser and sharper-tasting. Once the stalk is up, the plant has switched from making leaves to making seed, and it does not switch back. Oregon State University Extension notes that cilantro sown in midsummer typically flowers and sets seed wi four to six weeks, which is why a summer planting can seem to bolt almost as soon as it comes up.
Heat and day length are the main causes, working together. Cilantro is a . Warm weather speeds up its whole life cycle, and long days push it toward flowering. In the cooler, shorter days of spring and fall, the same plant can keep making leaves for several weeks or even months. That is why a sowing made about 2 weeks before your last spring frost often gives six to eight weeks of leaves, while one made at the start of summer may give little more than a handful before it flowers.
Stress tends to shorten the window further. Cilantro has a taproot and dislikes being moved, so nursery often flower sooner than plants sown where they grow. Dry soil, crowding, and a hot spot against a wall or pavement can all hurry it along. Plants in the coolest part of the garden usually hold longer than plants in full afternoon sun. Variety helps a little: types sold as slow-bolting, such as Slow Bolt and Leisure, tend to stay in leaf a week or two longer, but none of them stays in leaf through a hot summer.
Cut the leafy growth you have now; as the stalk rises, the leaves get sparser and sharper. Then decide what the plant is for. Left standing, the flowers draw hoverflies, lacewings, and small parasitic wasps that help keep aids down elsewhere in the garden. The green seeds can be used fresh, and seeds left to turn brown and dry on the plant become coriander. Cut the dry seed heads into a paper bag and let them finish drying there. A few plants allowed to dr seed may also give you volunteer seedlings when the weather cools.
Next time, sow small batches every two to three weeks from about 2 weeks before your last spring frost until early-summer heat arrives. Pause through the hottest weeks, then start again as late-summer heat breaks, so plants grow into cooler, shorter days. Sow seed in place rather than transplanting, choose the coolest spot you have (afternoon shade from taller crops helps), and keep the soil evenly moist. A fall sowing is often more productive than a spring one, because the plant is heading into weather that slows flowering rather than speeds it.
- AphidSoft, clustered insects on new growth causing curled leaves and sticky honeydew.
- Powdery MildewWhite powdery spots on leaves that spread into a floury coating — common when warm, dry days follow cool nights.
- Blossom DropFlowers fall before setting fruit, often during temperature extremes or after weather stress.
- Septoria Leaf SpotNumerous small circular spots with dark borders on lower tomato leaves, which then yellow and drop, progressing upward.
- Southern BlightWhite cottony mycelium and small round sclerotia at the stem base, with rapid plant collapse in warm, moist soil.
- Why did my broccoli skip making a head and go straight to flowers?Broccoli bolts when it experiences heat or stress during head formation — once it starts flowering, the head is unsalvageable, but timing adjustments can prevent it next season.
- When and how should I harvest herbs for the best flavor?Harvest herbs before they flower — leaf essential oil concentration peaks right before flowering, and flavor drops noticeably once the plant shifts energy to seed production.
- How do I save seeds from my garden plants so they'll grow true next year?Open-pollinated and heirloom varieties come true from saved seed; hybrids do not — and after selecting and fully drying seed, cold, dark, dry storage is the single biggest factor in how long viability lasts.
- What is a last frost date and how do I actually use it?Your last frost date is the average date of the final freezing night in spring — it's a probability, not a promise, and smart planting adds a buffer of 1–2 weeks beyond it for cold-sensitive crops.