How to Grow Asparagus In A Greenhouse

Asparagus spears are perennial stem vegetables that sprout every spring once they’re firmly established. They originate in South Africa, a dry climate, so they generally grow best during warm weather. Otherwise, they are relatively easy to plant and grow.

There are male and female asparagus plants, and the berry-producing female variety does better during cool winter weather. If you’re interested in growing asparagus, this article is a step-by-step guide on how to cultivate a healthy crop.

Requirements to Grow Asparagus in a Greenhouse

Since a warm, dry climate is the natural habitat for Asparagus, you want to plant your crop where it’ll get a minimum of 8 hours of direct sunlight daily. Although partial shade won’t kill the plant, you want it to be in full sunlight for the best results.

Asparagus doesn’t require a great deal of water, but it does need to be planted in loose, highly fertile soil that drains well. The earth is critical because the plant will grow new spears in the same garden every spring for more than 20 years, therefore, rich, fertile soil is required from the first day asparagus is planted.

To ensure that your soil is packed with nutrients, you should till compost into the area where your crop will be growing before planting the first bulb. Till two five-gallon containers of compost into every five square feet of soil where your plants will grow.

Thoroughly churning the compost into the soil adds vital nutrients you need for the long-term health of your harvest. It also loosens the soil and improves drainage and soil structure.

If you heat your greenhouse during the winter, you can plant seedlings or crowns whenever you wish to get your crop started. If your greenhouse is not heated, you need to wait for warmer weather for optimal planting conditions.

How to Grow Asparagus in a Greenhouse

Following a few simple steps, you can increase your chances of growing an abundant crop of delicious and healthy asparagus. Here’s what you want to do:

  • Prepare the soil by eliminating all the weeds from your planting area and tilling in two to four inches of manure, soil mix, or compost.
  • Dig six inches wide trenches about six to twelve inches deep. Expert opinions vary on the exact depth of your channels, but six inches are widely accepted as optimal.
  • Asparagus doesn’t grow as well when its roots are wet. Raised beds may be better if your planting area lacks proper drainage.
  • Plant your initial crop of one-year-old plants (called “crowns”) in the early spring, right after you enrich the soil with compost.
  • Build a mound in the trenches and plant the crowns 15 to 18 inches apart while spreading the roots over the ridge.
  • Cover crowns and roots with two inches of soil and water thoroughly.
  • Fill in the remainder of the trench with enriched soil after the spears grow. Leave three to four inches of stem exposed.
  • Once you’ve filled the trench, add four to eight inches of mulch and water at least once a month.

With the proper care, you will cultivate a thriving crop of asparagus year after year for your family to enjoy.

How Long Does It Take Asparagus to Grow in a Greenhouse?

Expect to wait two to three years before you can harvest an edible crop. But once the wait is over, you can expect an abundant harvest for 20 or more years. Patience is the key when growing asparagus.

Never harvest your crop in the first year. Allow the spears to vegetate to allow the crows to establish themselves.  Cut the dead foliage during late fall and side-dress with more compost.

In the second year, maintain a thick mulch in the bed, side-dress with compost in the spring and early fall, cutting down any dead foliage in the late fall.

Once established (usually in the third year), never harvest the same spears during the year, or you’ll kill the plant. Divide your garden so one area can rest while you harvest from another.

Rotate the resting periods among the plants so the vegetive spears can put nutrients back into the soil. These growing practices will encourage fast-producing plants that will sprout new spears every few days for several weeks during the spring.

Is Asparagus Easy to Grow?

It’s relatively easy to grow Asparagus. They’re drought-tolerant, so they don’t need very much water. If you want to harvest them year-round, it’s best to plant your crop in a greenhouse where you have maximum control over the temperature, light, and soil conditions.

Plants grown in the sun tend to grow compact and bushy, while shaded plants are more sprawling. You want to fertilize the plants monthly using a well-balanced brand. You must divide ferns every three years to avoid overcrowding other plants. If you grow your plants in containers, you’ll want to fertilize them every two weeks and divide them every two years.

Asparagus are hearty plants that are drought, disease, and insect resistant. So much so that the states of Hawaii, Florida, and Texas have categorized them as invasive weeds. Even the country of New Zealand has classified them as a weed because they overwhelm native species of plants.

While growing asparagus in the greenhouse is a good idea if you want year-round cultivation, you risk giving them too much sun. Try growing your plants next to a northern window to provide them with cooler temperatures.  

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