Plot · field guide
Why Lettuce, Spinach, and Cilantro Bolt (and How to Slow It)
You plant lettuce, spinach, or cilantro, and just as it looks ready it shoots up a tall stalk and turns bitter. That is bolting. Once it starts you cannot reverse it, so the whole game is slowing it down. These cool-season crops all bolt for the same reason, and the same six moves buy you weeks more harvest.
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What bolting is
Bolting is when a plant stops making leaves and shoots up a flower stalk to make seed. It is the plant racing to reproduce before summer.
The leaves turn bitter and tough almost as soon as the stalk appears, because the plant pulls its energy into flowers and seed. Cilantro can go from full leaves to a flower stalk in just a few days.
You cannot undo it. Once a plant bolts, pull it and replant. Everything below is about delaying that moment.
Heat and long days set it off
Two things trigger bolting: hot weather and long days. As spring turns to summer, days get longer and temperatures climb, and these cool-season crops read that as the signal to go to seed.
That is why they bolt fast in midsummer heat. Lettuce is ready in about 45 days, spinach in about 42, and cilantro in about 50, but a hot spell can send any of them to seed well before that.
Plant in the cool seasons, not midsummer
The biggest win is timing. Grow these crops in early spring and again in fall, when days are shorter and cooler. Skip the midsummer sowing, when heat sends them straight to seed.
A spring planting and a fall planting will out-yield anything you try to force through July.
Use shade cloth in the heat
When you are pushing the season and the weather turns hot, shade cloth cools the plants and buys time. A light shade cloth drops the temperature under it and slows bolting on lettuce, spinach, and cilantro.
It also keeps the soil cooler and damper, which these shallow-rooted crops like. Drape it on hoops over the bed on the hottest afternoons.
Pick often and choose the right seed
How you harvest matters too. Picking outer leaves often keeps a plant in leaf mode longer than letting it sit and mature.
Two more moves stretch the season further:
- Harvest the outer leaves every few days instead of waiting for a full head.
- Choose bolt-resistant or slow-bolt varieties, which are bred to hold in heat longer.
- Succession-sow small amounts on a schedule so a bolted patch is always replaced by a fresh one.
Succession-sow so you never run out
Instead of planting all your lettuce at once, sow a short row every week or two. When one batch bolts, the next is coming on behind it.
Sow spinach about every 7 days, lettuce about every 10 days, and cilantro about every 21 days, and you keep a steady supply instead of a single crop that all bolts together.
Questions, answered straight
Heat and long days signal the plant to stop making leaves and shoot up a flower stalk to set seed. The leaves turn bitter fast. Spinach and cilantro bolt for the same reason, and you cannot reverse it once it starts.
No. Once the flower stalk appears the leaves turn bitter and the plant will not go back. Pull it and replant. Everything you do to prevent bolting has to happen before the stalk shows.
Plant in cool early spring and fall, not midsummer. Use shade cloth in heat, pick outer leaves often, choose bolt-resistant varieties, and succession-sow small amounts so a fresh batch is always coming on.
In the cool of early spring and again in fall, when days are shorter and cooler. Avoid midsummer sowings, which bolt fast in the heat. Sow small amounts every 7 to 21 days for a steady supply.