Grow Light for Cilantro Indoors Without Fast Bolting
A grow light for cilantro indoors works well when the room stays cool, since heat plus long warm days push cilantro to bolt. Utah State University Extension advises soil below 75F indoors, especially near a heat source or a warm window. Set the lamp close, place pots away from heaters plus sow new pots every few weeks.
The short answer
Give indoor cilantro bright light in a cool room. Penn State Extension advises herbs sit 6 to 12 inches from two fluorescent bulbs for 14 to 16 hours. Utah State University Extension advises soil below 75F. Sow seed in a deep pot plus resow every two to four weeks for a steady leaf supply.
Why does cilantro bolt so quickly indoors?
Penn State Extension notes hot temperatures make cilantro quick to flower plus set seed, a response called bolting. Oregon State University Extension notes temperature plus day length both influence flowering. In cooler shorter days, plants grow leaves for several weeks or months before they flower. Pots near a heater bolt sooner.
| Factor | Guideline | Source |
|---|---|---|
| Soil temperature | Below 75F | Utah State University Extension |
| Fluorescent distance | 6 to 12 inches | Penn State Extension |
| Light hours | 14 to 16 hours | Penn State Extension |
| Leaf harvest size | About 6 inches long | Utah State University Extension |
| Resowing | Every 2 to 4 weeks | Penn State Extension |
Source: Utah State University Extension plus Penn State Extension.
How bright should the light be for cilantro?
Utah State University Extension notes cilantro grows well in full sun. Penn State Extension notes most herbs need 6 hours of direct sunlight, or a spot 6 to 12 inches from two fluorescent bulbs for 14 to 16 hours. Turn windowsill pots often so every side gets light. Thin pale stems show the lamp is too far away.
Why sow cilantro every few weeks?
Penn State Extension advises sowing seed every two to four weeks for a continuous supply. Oregon State University Extension calls this succession planting plus notes the long taproot makes transplanting difficult. Sow straight into a deep pot, since Penn State Extension notes herbs with a taproot belong in deep containers.
How to: step by step
- Fill a deep pot with drainage holes with potting mix.
- Sow cilantro seed straight into the pot.
- Hang the grow light 6 to 12 inches above the seedlings.
- Run the light 14 to 16 hours a day on a timer.
- Set the pot away from heaters plus hot windows.
- Harvest outer leaves when they are about 6 inches long.
Troubleshooting
Tall flower stalks: heat or plant age. Cool the room plus resow.
Thin pale stems: low light. Lower the lamp.
Wilting after transplant: taproot damage. Next time, sow in place.
For more on lighting see grow lights for cannabis, grow light timers, grow light heat management plus cannabis seeds. Kind Seed Co also stocks seeds for indoor growers.
Sources
- Cilantro/coriander in the garden, Utah State University Extension
- Cilantro, a unique culinary herb, Penn State Extension
- How to grow cilantro for leaves or coriander seeds, Oregon State University Extension
- Growing herbs indoors, Penn State Extension
FAQ
How long does indoor cilantro last before bolting?
It depends on warmth plus day length. Oregon State University Extension notes cilantro planted in midsummer bolts plus sets seed within four to six weeks, while plants in the cooler shorter days of spring or fall grow leaves for several weeks or months. A cool indoor room slows bolting.
What happens to leaves after cilantro bolts?
Penn State Extension notes bolting results in bitter tasting leaves. The plant shifts its energy to flowers plus seed, so leaf growth slows. Oregon State University Extension notes bolting is not entirely negative, since the seed is coriander. For a steady leaf supply, sow a fresh pot every few weeks under the lamp.
Is cilantro the same plant as coriander?
Yes. Utah State University Extension refers to one plant as cilantro or coriander. Oregon State University Extension describes growing the same plant for leaves or for coriander seeds. Indoors under a grow light, most growers harvest the leaves before the plant bolts plus sets seed, then sow again.
Does cilantro need full sun indoors?
Utah State University Extension notes cilantro grows well in full sun. Penn State Extension notes most herbs need 6 hours of direct sun. A winter window rarely gives that much, so a grow light 6 to 12 inches above the pot fills the gap while the room stays cool.
How deep should a cilantro pot be?
Deep enough for the taproot. Oregon State University Extension notes cilantro has a long taproot that makes transplanting difficult. Penn State Extension advises growing herbs with a taproot in deep pots. Sow seed straight into the final pot with drainage holes so the root never has to move.
