Rainline Garden My garden plan
A dense patch of cilantro leaves
Photo: Pexels

When to plant cilantro in Ontario, OR

Plant cilantro from seed, directly in the garden in Ontario, Mar 20 – May 8. For a fall harvest, plant again Aug 26 – Sep 9.

Easy Plant seeds in the ground

Difficulty
Easy
Sun
Full sun; afternoon shade in summer
Spacing
4 inches apart
Planting depth
¼ inch deep
Frost
Handles light frost
First harvest
About 50 days after planting

Why these dates

Ontario's typical last spring frost is April 21. As a cool-season crop that handles light frost, this crop doesn't need to wait for that date. In the Columbia Basin and low eastern valleys, though, the soil usually isn't ready to work until about March 20.

Columbia Basin and low eastern valleys. Hot, dry summers and quick spring warm-up. Warm crops go in earlier than west of the Cascades, and irrigation matters more than rain.

How to grow cilantro in Ontario

  1. Prepare the bed: loosen the soil and mix in an inch or two of compost.
  2. Plant seeds Mar 20 – May 8, ¼ inch deep, 4 inches apart.
  3. Keep the soil evenly moist until sprouts appear, which can take one to three weeks in cool soil.
  4. Plant again Aug 26 – Sep 9 for a fall harvest.
  5. Harvest: Cut leaves once plants are about 6 inches tall. If it bolts, let it go to seed and harvest the coriander.

Key numbers

Growing notes

What makes the difference in Northwest gardens, in plain language.

Soil and sowing

Cilantro grows best in fertile, well-drained soil with a pH of about 6.2 to 6.8 and steady moisture. It has a taproot and doesn't transplant well, so sow it directly where it will grow. Each round "seed" is actually a husk holding two seeds; gently cracking them before sowing can speed sprouting. Keep the soil damp until seedlings appear, usually within one to three weeks.

Why cilantro bolts

Cilantro is programmed to flower once days grow long and warm. Heat, dry soil and crowding all speed it up. Once a tall flower stalk rises, the leaves turn thin and feathery and the flavor changes. You can't stop it, but you can work around it: sow a short row every three weeks, give summer sowings afternoon shade, and grow slow-bolt varieties like Calypso, Santo and Leisure. In the Northwest, the most reliable crops come from early spring and late summer sowings. East of the Cascades, summer heat ends spring cilantro quickly, so early sowing matters even more.

Harvest, coriander, and winter

Cut leaves once plants are about 6 inches tall, taking the outer stems and leaving the center to regrow. Fresh cilantro keeps a week or so in the fridge with stems in a glass of water and a bag over the top. If plants bolt, let them flower: the blooms feed beneficial insects, and the seeds become coriander. Harvest when the seeds turn tan and dry them in a paper bag. West of the Cascades, a late summer sowing often survives mild winters and gives a spring harvest.

Common questions

When is the last frost in Ontario, OR?

Typically April 21. In 9 years out of 10, frost is over by May 8. These are 1991–2020 NOAA climate normals for Ontario Municipal Airport.

Is it too late to plant cilantro in Ontario?

The spring planting window runs through May 8. If you miss it, plant again for fall from August 26 to September 9.

How long until I can harvest cilantro?

About 50 days after planting. Cut leaves once plants are about 6 inches tall. If it bolts, let it go to seed and harvest the coriander.

Why does my cilantro keep going to seed?

Cilantro naturally bolts as days lengthen and warm up. Sow small batches every few weeks, grow slow-bolt varieties, and give summer plantings some shade. Spring and fall crops last much longer than summer ones.

Can I grow cilantro from coriander seeds?

Yes. Coriander is cilantro seed, and whole seeds from the spice aisle often sprout. Seed packets sold for growing are more reliable and may be slow-bolting types.

How do I harvest cilantro so it keeps growing?

Cut the outer stems near the base and leave the young center stems in place. Take no more than about a third of the plant at once. It will keep producing until it starts to bolt.

Also plant in Ontario around the same time

Planting dates for cilantro in nearby areas

Full planting calendar for Ontario · Cilantro in every city