The calendar may say “Spring” but here in Colorado it’s still winter. Still, the first signs of spring are there if you look for them. Days are getting longer. Birds are wearing their courting feathers and breaking into spontaneous song. Buds are swelling on bare branches. And gardeners are reemerging from their winter hibernation.
Hopefully, you’ve already tested any stored seeds for viability, then placed your seed order or picked from the racks at your local garden center. When your packets arrive, store them in a cool, dry place. I like to sort mine into zip-lock baggies, then arrange the bags in a clear plastic shoebox. Colorado is naturally dry, but reusing the bags of desiccant that come in products such as new shoes and purses will help in more humid regions.
When should those new seeds be planted? I count back from my average last frost date, then mark it on my calendar. At this point it’s an act of faith—our early spring snows always make me wonder if summer is really coming! The following charts show when to plant some popular flowers and vegetables:
When to Plant Outside
|Frost-tolerant annual flowers: cornflowers (bachelor buttons), pansies, snapdragons. Frost-tolerant herbs & vegetables: broccoli, bok choi, cabbage, cauliflower, celery, cilantro*, kale, kohlrabi, leeks, lettuce, onions, peas*, spinach**, turnips||Plant outside between April 15 and May 15, depending on weather forecasts and your elevation. May also be grown for fall. Plant in July. Plants will mature in the cooler fall weather. Make sure vegetables have time to produce a crop before October 10, the average first frost date for Colorado Springs. (Add or subtract a day for every 100 feet change in elevation below or above 6,300 ft.).|
|Cool weather annual flowers:
sweet alyssum, calendulas, sweet peas. Cool weather herbs & vegetables: beets*, Brussels sprouts, carrots*, chard, Chinese cabbage, collards, mizuna, mustard, parsnip, parsley, radishes*
|Plant outside around May 15, the average last frost date for Colorado Springs. (Add or subtract one day for every 100 feet change in elevation above or below 6,000 ft.).|
|Warm weather annual flowers:
cosmos, lobelia, marigolds, petunias, sunflowers, zinnias. Warm season herbs & vegetables: basil, beans*, corn*, cucumbers, eggplant, melons, okra, peppers, pumpkins, squash, tomatoes, zucchini
|Plant outside late May to early June, when the soil is thoroughly warm and all danger of frost is (hopefully) past. Temporarily using a plastic mulch, and/or covering the plants at night will help to keep warmth in the soil until summer truly arrives.|
* Work best if direct seeded in the garden
** Spinach works best as a fall crop, as exposure to days longer than 14 hours will cause it to become bitter and bolt.
When to Start Seeds Inside
|Start seeds 10 – 12 weeks before setting out as transplants:||Slow growing flowers and vegetables: geraniums, petunias, lobelia, snapdragons, onions, leeks, celery|
|Start seeds 6 – 8 weeks before setting out as transplants:||Parsley (benefits from pre-soaking seed overnight), peppers, tomatoes, eggplant|
|Start seeds 4 – 6 weeks before setting out as transplants:||Faster-growing flowers such as marigolds, Asian greens, broccoli, Brussels sprouts, cabbage, cauliflower, lettuce, Swiss chard|
|Start seeds 2 – 4 weeks before setting out as transplants:||Fastest-growing flowers such as zinnias, cucumbers*, squash*, melons*, basil, corn**. Transplant squash, melons, and corn carefully to avoid disturbing roots.|