When to Plant Cilantro in Colorado

Slow-Bolting Varieties

• The climate of Colorado falls within U.S. Department of Agriculture plant hardiness zones 3a to 7a, which bodes well for cool-seeking cilantro. If summer temperatures in your area run 75 degrees Fahrenheit or lower, you may be able to keep successive plantings of cilantro going all summer. But if you live in an area of Colorado that sees warmer summers, you can slightly extend your spring growing season by planting a variety that is slow to send up the seed stalk. The Colorado State University Cooperative Extension recommends slow-bolting varieties, such as "Caribe." According to The Old Farmer's Almanac, "Costa Rica," "Leisure," and "Long Standing" also fall in the category of cilantro varieties that are slow to produce flowers and seed.

Planting Times

• Early spring and fall, when soil temperatures fall between 55 and 60 degrees Fahrenheit, are the best times to germinate cilantro to take advantage of the cool temperatures that cilantro craves and to encourage it to grow longer before flowering and going to seed. Spring planting commences from two weeks before to just after the last frost date, which ranges from late April to late July in Colorado, according to the CSU Cooperative Extension. Late summer to early fall gives you an opportunity for a second crop before freezing temperatures set in.

Growing Conditions

• Although cilantro prefers cool growing conditions, it needs sun, not complete shade. Plant it in a cooler part of the garden with light shade or full sun to encourage the fast growth necessary to beat a summer heat wave or winter's hard freeze. This herb grows best in moist, well-draining soil. If your local climate remains below 75 degrees Fahrenheit all summer, you can make successive plantings of cilantro every 14 to 21 days all summer for a continual supply.

Germination Time

• The time from seed to cilantro harvest takes about 45 days, reports the Burpee seed company. Direct seeding of cilantro or coriander seeds produces germination in about 10 days to three weeks, and plants quickly grow up to 3 feet tall. Three to four weeks later, the leaves are ready to harvest. Therefore, when deciding when to plant cilantro, calculate enough time before the warm weather sets in for your cilantro to mature so that you don't lose the whole crop to seed. Should unseasonably warm days surprise you, you can always harvest the seed for later use or allow it to self-seed and come up on its own in the following fall or spring.