The indoor seeding season has begun for ornamental annuals that need longer than eight weeks to grow to transplant size. Refer to the planting chart for several ornamental annuals on this recent blog - Seeding and Transplanting Ornamental Annuals.
It's also time to direct seed indoors certain cool season vegetables, especially if you're using cold frames for earlier planting in March. Check out the planting chart below.
For newbies to Colorado there
are three overlapping seasons to plant outdoors.
- The first cool season planting period
ranges anywhere from March to the middle of May. These include
cool weather loving vegetables like spinach, peas and beets and cool season annuals
like pansy, calendula and sweet peas.
- The warm season window is anywhere from mid-May to the first of July and
includes vegetables like - tomatoes, peppers, squash and
corn, herbs like basil, plus annuals - petunias, marigolds, sunflowers and cosmos.
- Hardy
perennials, shrubs and trees can be planted during the warm season period and
all the way to early fall. The exception is to try to avoid planting
when temperatures are extremely warm (85+). It can be done, but pay close
attention to watering and providing some shade for a few weeks.
- Exceptions - bare root roses, plus bare root trees and shrubs can be planted almost anytime the soil is workable (not too wet) from March to late April or so.
- Mid-summer is when the
third season planting window begins - mostly cool season vegetables that
mature in sixty days or less and warm season crops that also have a
shorter maturity date like summer squash, okra and basil.
Keep in mind that cool season direct
seeding or transplanting is all dependent on the weather - if snow is on the ground or
it's raining or snowing from March to late May, the cool season
planting window may either be delayed or skipped. Using tunnels, row
covers and cloches are recommended if the weather isn't cooperating with your planting plans.
Knowing the last spring frost dates and planting windows will help you
plan your schedule for seed purchases (don't delay much longer) and
indoor seeding for planting during the correct window - cool or
warm season.
The timing and planting information on seed packets vary
per company. Some mention soil temperatures or map zones as guides to
direct seed outdoors, or a certain number of days from frost dates to
start seeds indoors. Familiarize yourself with the
seed packet information. Check out this helpful article - Garden Primer How to Read a Seed Packet. I'm suggesting to use May 15 as the probable final spring frost date, but we know not to bet the house on that date. In 2007 the last spring frost was June 8.
If you miss the window to start your seeds indoors,
you can always purchase cool season transplants at garden centers
starting in late winter into spring, and later in the spring for
warm season plants.
Warm season seeds are generally started indoors in
April for late May transplanting. I'll post the warm season and herb planting charts soon.
Please be aware that some cool season vegetables prefer being directly seeded outside in soil and not started inside, like arugula and other greens. Whereas some vegetables can be seeded indoors for transplanting later outdoors or directly seeded outside, like kohlrabi. Some vegetables are perennial, so chose your site carefully because they won't like being moved. Click here for early - soil preparation.
Cool Season Vegetable Seeding and Transplanting Chart
(a few herbs are included):