Guest Contributor: Cassey Anderson, Horticulture Agent, Colorado State University Extension
Get your garden plan in place before planting season begins
Depending on where you live, March and April when many gardeners are really getting things going. February is a great month to get a plan in place for what you want to start, when, and where. Let’s talk about how to decide when to plant what and also dive into some perennial plant choices that can be planted in spring.
Early spring can be a busy time, and there is a lot that you can plan to get started. In cooler temperatures you can plant early, and cool season crops such as peas, kale, radish, spinach, lettuce, onions can go in, some as soon as the soil can be worked. Warm season crops such as cucumbers, melons, tomatoes, peppers, squash etc. may have to wait a little while but get your plan in place.
What’s the difference between a warm season crop and a cool season crop?
Mostly the difference is in the temperatures the plant can 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 growing 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.
Cool season crops will bolt as weather warms
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 (I like using leftover takeout containers), place the seeds in with it for 12-24 hours at room temperature. Many crops, even the cool season crops like to germinate between 70 and 80 F.
See this Colorado Master Gardener Garden Note for specific crop temperatures, view this resource from CSU.
Warm season plants, contrasted to cool season do not tolerate those cool or cold temperatures. Rather, they like to both germinate warm and grow warm. Typically, it is best to keep seedlings warm (if you’re comfortable, they will be as well) and wait until soils and air temperatures warm above 55-65 degrees. Some crops, such as tomatoes, are likely to be set back, sometimes for much of the season if you plant them too early, so it is better to be cautious and ensure that conditions are right. If you do want to get a jump on the season you can warm the soil with low tunnels, wall-o-water, or plastic mulch, but be sure to keep an eye out for air temperatures especially in the evening.
Plant perennials in Spring
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.
Planting Asparagus
You may need to wait 1-3 years to harvest, but asparagus will keep producing for many years after!
Asparagus can produce for over 15 years in a vegetable garden. You can start from seed but buying crowns will allow you to harvest in around 3 years instead of upwards of 5 years. 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 (you can get away with harvesting sooner for crowns, longer for seeds), or until you begin to see numerous spears poking up. In the first year of harvesting keep it light, 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.
Planting Rhubarb
While only botanically speaking a vegetable rhubarb is a very easy plant to maintain in the garden. Plant crowns in spring around your last freeze date and water well. Keep irrigated if necessary through the summer and you can often harvest as early as the following spring. Try not to harvest more than about 30% of the plant at a time but you can harvest for a month or two in spring.
Herbs for the perennial garden
Herbs can also be a great addition to the perennial food garden. Some herbs may be hardy and perennial in your growing zone and others may need to be replanted annually. But overall you can seek out plants such as chives (often perennial), thyme (often perennial), oregano (often perennial), rosemary (sometimes perennial), mint (often perennial but potentially aggressive), parsley (often annual but re-seeds readily), dill (annual but reseeds readily)
Some other fun perennials that you may not have tried:
Jerusalem artichoke – root vegetable that has lovely golden flowers. Technically not a perennial per-se but you always miss a few when digging which will make next years crop!
Dandelions (for greens!) – you can buy fancy dandelion varieties or plant seeds intentionally in an area you water and fertilize to harvest the greens for salads. The flowers can also be used to make various jellies and extracts. Do not harvest dandelions that have been treated with pesticides.
Horseradish – a perennial root that gives a kick horseradish can be a good addition to the garden. Be sure to let it take up some space but ensure you dig out roots after 1-2 years of growth. If you don’t plan to use it one year it may be good to dig the roots to ensure they don’t spread too far.
Walking Onions – a unique way to keep onions in your yard all year round, walking onions have a flower head that makes little onion bulbs. As the bulbs mature they sink to the ground and set roots. You can use the stems or the bulbs for any onion recipes.
As always, reach out to your local Extension office for further information if you have any questions.
Happy Gardening!
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