How to Grow Asparagus

Asparagus is a perennial vegetable whose green and purple stalks elevate even the simplest spring dish. In addition to its culinary appeal, asparagus provides an excellent source of vitamin K and folate (essential for red blood cell formation). Plus, it’s a low-effort crop, meaning beginning gardeners can learn how to grow asparagus just as easily as the pros. 

Follow the steps below to plant your asparagus patch – one that will produce a tasty harvest for up to 20 years. 

Step 1: Select a Location

If you’re thinking about growing asparagus, first consider where you’ll plant your asparagus bed. Asparagus is not a fussy plant once well-established. However, it’s essential to choose the right location for your asparagus patch because once you’ve put these plants in the ground, you really shouldn’t move them. (It isn’t easy to dig up the plants without severing the roots, especially during the first few years while roots are still strengthening.)

Make sure to follow these key specifications for choosing the best location for your asparagus patch. 

Key Specifications for the Perfect Asparagus Patch

  • Growing Zone: Zones 3-8 
  • Sunlight: 8+ hours of full sunlight per day in summer
  • Soil: Loose, well-drained
  • Water Table: well below the bed year-round

Avoid growing asparagus in containers as constrained spaces reduce their lifespan.  Since asparagus patches take up to 3 years to establish, a reduced harvest life of 3-4 years might not be worth the effort. 

Step 2: Acquire Seeds or Crowns

Neither option will negatively affect the taste or quality of your harvest, so this decision comes down to personal gardening preference and timeline. 

Grow Asparagus from Crown

Crowns are the roots of a 1-2-year-old asparagus plant, attached to a small base from which the sprouts will emerge.

When you order crowns through the mail, they will likely be somewhat dry and brittle upon arrival. If this is the case, be sure to soak crowns in a bucket of water for an hour before planting. 

Grow Asparagus from Seed

Start your seed trays in February if you’re determined to plant your asparagus from seed.

Asparagus seeds can take 21 days or more to germinate and then several weeks for the seedlings to emerge. Once the seedlings are 2 inches high, they are ready to be transplanted into your growing bed.

Here is a video that goes into more detail on starting asparagus from seed indoors.

Whether you shop at a local nursery or online, try to buy male plants as they tend to produce more spears than female plants. 

Step 3: Prepare the Soil 

Once you’ve selected a good location for your asparagus bed, you’ll need to build a trench for your plants. Assuming you’re planting crowns, you can begin this process in March or April (as soon as the soil is easy to work with). 

Each plant will require a space 6 inches deep and at least 12 inches wide. The length of your trench will depend on how many plants you want in a row. For example, if you wanted to plant five crowns in a row, your trench would need to be 6 inches deep, 12 inches wide, and 72 inches long. If you are planting multiple rows, be sure to leave 12 inches of space between each row.  

After digging your trench, use a digging fork to loosen the soil at the bottom. Asparagus prefers sandy and well-drained soil with a pH of 6.5 – 7.5 (PDF). If your soil is not naturally well-drained, add sand or compost to the bottom of the trench. If your soil is too acidic, try liming the soil (PDF with lime formula) to bring down the pH level. It’s also a good idea to add either a finished compost or well-rotted manure to the bottom of your trench. 

Although some gardeners recommend applying salt to your asparagus bed, avoid doing this as salt can seriously damage soil quality. Instead, add phosphorus-rich amendments such as bone meal, composted manure, or rock phosphate. 

Step 4: Plant the Plants!

Use the mixture at the bottom of your trench to ‘hill up’ the soil and promote proper drainage. Place your pre-soaked crowns, crown side up, along both sides of the ridge. Since you’ve created raised rows at the bottom of your trench, you’ll be able to lay the roots at an angle most helpful for growth.  

Again, be sure to evenly distribute crowns, leaving 12 inches of space on each side of the plant. Fill in the trench, covering all plants with 4 to 6 inches of soil, and water well. 

Step 5: Harvest Your Crop

One of the hardest things about planting asparagus is resisting the urge to harvest your crop the first year after planting. Asparagus plants require two to three years to form deep roots. The strength of these roots is vital to cultivating a prolific and long-lasting asparagus patch. 

If your crop produces well the second year after planting, you can harvest a few spears (about 25% of your crop) so long as the stalks you harvest are at least six inches tall. Don’t worry – once you’ve made it to the third year after planting, you can begin to harvest normally. 

Harvest asparagus when spears are 5-7 inches high. (Any higher, and your asparagus will be tough and stringy.) If the days are warm, you’ll want to harvest every two to three days. You can use a sharp knife or simply snap them off with your hands. 

harvest of asparagus

Your patch might produce spears for up to 10 weeks, giving you plenty of time to perfect your technique for grilling asparagus (recipe allrecipes.com).  

Step 6: Maintain Your Asparagus Bed

Water the plants throughout dry spells during the summer, but be sure not to overwater as this can lead to root rot. One method of watering is to install a drip irrigation system to ensure your asparagus bed stays hydrated without getting damp.

While harvesting your spears, pull up any weeds – be careful not to disturb the asparagus roots.

Although asparagus is relatively resistant to pests and disease, keep an eye out for asparagus beetles. While you can use a food-safe solution (such as soapy water) to remove these bugs, the simplest way to get rid of them is to pick them off the stalks one by one.  Then, you can put the beetles into a container with soapy water to kill them.

At the end of the harvest period (around the beginning of June, depending on where you live), allow your asparagus plants to grow large and feathery. This bushy growth will help the asparagus gather and store the energy necessary to power them next spring. 

But until then, happy eating!

Videos on Growing Asparagus

This video will give you a great visual of growing asparagus from crowns. As it’s not a common term, and most people have never heard of it. The tip on storing the roots/crowns in coco peat is also great if you can’t get to planting right away due to weather, etc.

Even though most people don’t have the patience for growing asparagus from seed, this video will give you some more information if you choose to go that route.

Companion Plants with Asparagus

If you’re wondering about companion plants for asparagus, one good choice is strawberries. They work well together when interplanted in the same bed.

The above video also covers planting beds and growing asparagus from crowns.

This video shares a good tip on when you harvest: place the asparagus into cold water right away to help preserve nutrients.

Later in the video shows the asparagus beetles and their eggs (don’t worry, the beetle eggs are easily removed when you rinse with water).

If you’re wondering if you should mulch your asparagus bed, this video will help. Mulch is beneficial for asparagus and should be loose to soak in water.

Materials you can use for mulch:

  • Pine shavings
  • Bark mulch
  • Straw
  • Pine needles

These are all good choices. Avoid synthetic mulch like landscape fabrics, or black plastic. Along with any mulch that is dyed. You only want to use natural materials.

Growing asparagus in a raised bed using the Mary Washington variety. Plus, information on saving seeds.

How to Propagate Asparagus

Now that you have a successful harvest. You might be wondering how to propagate asparagus, which may be easier than you think.

In the spring, trim back the old dead fern. Then dig up the main root ball and use a garden hose to wash the soil off.

Use a shovel to divide the root ball into multiple plants. Make sure there are at least a couple of shoots on each plant.

You now have created new asparagus crowns. Simply follow the instructions above for planting crowns. Here is a video that demonstrates propagating:

FAQ’s

What is the oldest asparagus patch in the world?

While nothing has been confirmed as the oldest asparagus patch in the world, there seem to be numerous statements of 100-200-year-old patches.
The keys to making your plants last are good soil, water, and dividing them properly. Do that, and your asparagus plants may outlive you.
Also, if you want a self-sustaining patch, you will want to make sure you plant a variety with females. As they produce seed, male-only types like Jersey-Knight will not.

References

PubMed on folate: pubmed.ncbi.nlm.nih.gov/15189115/

100 to 200-year-old asparagus patches: permies.com/t/75517/long-asparagus-bed