Asparagus is a tall, perennial vegetable with fern-like leaves, but we’re after those tasty early shoots called spears. It can be harvested as one of the first spring vegetables, making it an excellent choice for home gardeners.
Establishing an asparagus patch in your garden requires patience, but you’ll enjoy continued production for 10-15 years or more. This guide will show you how to plant and grow asparagus so you have years of tasty, nutritious, and tender spears.
Where to Plant Asparagus
Asparagus needs a site with full sun. Soil should be fertile, loose, and well-drained. Excessive soil moisture can cause root rot of the crowns. Growth is best with soil pH in the 6.5-7.0 range. If your soil test indicates a significant adjustment is needed, try to do so the year before planting.
Your asparagus bed will live a long time, so get a soil test every three years to understand what amendments your soil may need.
Keep the summer size of asparagus plants in mind–the tall ferns can shade out shorter plants. Consider a location on the north side of your garden or a separate bed so they won’t shade out other plants. Like other perennial plants, choose an area where they can remain for years. You don’t want to move the plants just when they start to hit their stride.
How to Plant Asparagus Crowns
Asparagus beds are most commonly planted with crowns–one-year-old plants. Keep the crowns refrigerated after they arrive until you are ready to plant. Visit this guide from the University of Minnesota Extension for more helpful information about how to plant asparagus.
- Before planting, amend the soil with aged manure or compost.
- Dig trenches 6-12 inches deep and several inches wide in the soil. Keep the excavated soil next to the trench; you’ll use it later. Space rows 3-4 feet apart.
- Lay the crowns in a line, 12-18 inches apart, in the trench. They should line up heel-to-toe. It’s okay if some roots overlap.
- Cover the crows with 2-3 inches of soil and water thoroughly.
- The soil may settle after the first watering. Add more soil if any roots are exposed.
- In 2-3 weeks, little spears will pop up. Once they are several inches tall, add a couple more inches of soil to the trench, similar to hilling potatoes. Repeat this process until the trench is completely filled in.
- Mulch with straw, pine needles, chemical-free grass clippings, or shredded leaves to suppress weeds and retain moisture.
How to Plant Asparagus Seeds
Asparagus seeds are available from online vendors, or you can try collecting your own from existing plants. You’ll need to start these seeds early–they take some time to get going.
- Plant seeds 12-14 weeks before the last frost date in 2-inch cells or pots.
- Sow seeds ½ to 3/4 inch deep.
- Keep moist and warm–asparagus seeds germinate best at around 75℉.
- Harden seedlings off before planting outside. Plant seedlings in the same manner as crowns.
How to Grow Asparagus
Asparagus is quite happy to do its own thing throughout the year with little care from you once established. Remove the old ferns in the fall, and keep the weeds down with mulch or hand weeding.
Watering Asparagus
Keep asparagus plants well watered, especially in the first year. While asparagus won’t often show signs of wilting or dehydration, adequate soil moisture is still important. If your rain gauge has been dry, provide about an inch of water per week to your asparagus bed, more if in sandy soil.
Mulching will help to minimize soil moisture swings, reduce weeds, and keep the soil cool and healthy.
Fertilizing Asparagus
Amending the soil with aged manure, finished compost, or fertilizer before planting will go a long way toward starting your asparagus bed correctly. In subsequent years, add soil amendments in early spring before spears pop up in mid-summer after harvest.
Don’t forget the soil test every few years. Too much fertilizer can build up in the soil and cause problems. If choosing a fertilizer, a balanced 10-10-10 NPK product will work fine. Apply at the rate listed on the package.
FAQs
What is the growth time of asparagus?
Asparagus is ready for its first harvest two years after planting crowns or three years after starting from seed (crowns are just one-year-old plants). If starting from seed, add a year to the below guidelines.
Don’t harvest spears during the first growing season to allow asparagus patches to grow large and healthy.
You can sneak in a light harvest the second growing season if the plants were vigorous the year before, but limit any harvest to only a week or two, and don’t take many–just a tasty teaser. Many gardeners won’t harvest the second season either.
Your asparagus should be ready for a full harvesting season in the third year.
How do I harvest asparagus?
The most important question of all! Harvest spears in spring when they are 6-10 inches tall and before buds open. Cut or break spears at the base at ground level. A short-bladed paring knife works well.
Keep checking often–asparagus spears can sometimes grow two inches in a day. Once they get large and fat, they get woody and aren’t as tasty.
When is asparagus season?
Asparagus spears start popping up in spring when the soil temperature warms to about 40℉. Keep harvesting new spears every few days for about 6-8 weeks. After that, leave the spears to grow into full-sized ferns, allowing the plants to store energy for the following year.
Asparagus Varieties to Grow
Purple and green varieties are available; some are more cold-hardy, disease resistant, or have more male plants–bigger spears– than others. These perennial favorites are a great choice and will provide many years of harvests.
- ‘Martha Washington’
- ‘Sweet Purple
- ‘Jersey Knight’
