April is the month when many gardeners are really getting things going.
Perhaps you’ve planted some peas or kale in the vegetable garden already, perhaps you’re just getting things underway. Regardless, April is a busy month. You can plant your cool season crops: radish, spinach, lettuce, green onions etc. You can start warm season crops indoors: cucumbers, melons, squash, pumpkins etc.
What’s the difference between a warm season crop and a cool season crop?
Mostly it’s in the temperatures they’re willing to tolerate, and those that they will grow well in. Cool season crops can tolerate cold temperatures, and some can even tolerate light freezes (defined as anything between 28 F and 32 F). These crops are also typically done with their season by the time we really warm up in July. Many of these crops have produced their final fruit or bolted, i.e. gone to seed, once daytime temperatures go up into the high 80s or 90s.
One thing that can be a little surprising for many of our cool season crops is that although they like to grow in cool temperatures, they germinate better and more quickly with warm temperatures. You can pre-germinate many of the cool season crops: peas, lettuce, kale, onions etc. Soak a paper towel and put it in a ziplock bag or other sealable container, place the seeds in with it for 12-24 hours at room temperature. You can get them warmer, many crops like to germinate between 70 and 80 F. See this Colorado Master Gardener Garden Note for specific crop temperatures:
You can get your perennial garden going as well: asparagus, rhubarb etc. are good to get started in mid- to late-April. Perennial crops may take a few years to get their feet under them before harvest, but you can subsequently enjoy even decades of low-effort production.
Asparagus can produce for over 15 years in a vegetable garden. You can start from seed but buying crowns will give you some time advantage. Choose a sunny, well-drained area, preferably somewhere not prone to freezes in your yard (not low-lying for example). Amend the soil with a well-rotted compost if needed. Plant crowns deeply in a 6-12” trench, cover lightly and bury as the crowns grow up. Place crowns “head to toe”, root tip to bud tip, typically with the crowns about 12” apart. Water regularly so the crowns do not dry out. Plant seeds about 1” deep, they may take up to 3 weeks to germinate. Mulch well for winter. Do not harvest for the first 1-3 years (sooner for crowns, longer for seeds), or until you begin to see numerous spears poking up. In the first year you should harvest for about two weeks and let the remaining spears turn into ferns that will feed back into the plant overall. In subsequent years you can harvest for 4-6 weeks, usually into mid-June or early July.
If you have specific questions be sure to reach out to your local county Extension office.