Asparagus (Asparagus officinalis)

For whatever reason, the first appearance of asparagus in my garden seems almost magical.  One day it’s just empty dirt, the next day baby spears of deliciousness have erupted through the surface.

(All links open a new page, so you won’t lose your spot when you look around!  Get information on gardening and cultural traditions, recipes, stories, and more!)

*A handy growing summary chart is at the end of the article.*

Asparagus is relatively easy to grow, but they do have some factors to consider if you want to ensure a decent crop from one year to the next.  They are also long lived, upwards of 25 years or more, so you also want to make sure that where you plant them is going to be a good spot for a long time to come.

Cultivars:

Thanks to modern cultivation, you can select varieties that will offer a larger harvest than that of previous types, as well as different colors (purple and green), and disease resistance.  Heirloom varieties are also widely available, and though they may not be as prolific, they make up for it in flavor.

For example, there are a few different cultivars in the “Jersey” named series.  These are all male plants and so they don’t use energy producing seeds.  This means more energy will go towards stalk production.  They also offer resistance to fungal diseases that could cause rotting of the roots.  However, properly timed pruning and good soil drainage can help overcome those problems in female or non-disease resistant plants.

By the way, you may have heard of or seen white asparagus.  This is not caused by variety, but by growing method.  If you really want those white asparagus stalks, you will need to ensure that the plant is given zero sunlight during the entire time of harvesting.  It is the light that triggers the production of pigments in the plant.  This will mean either covering the area with black plastic elevated above the ground so that the stalks can grow, or to continuously pile soil over the plants to keep the sun from reaching the stalks.

Growing Conditions:

No matter what variety you grow, all will need well-draining soil, consistent moisture, and space free from competition.  Plants are usually sold as “crowns”, which is similar to how bare root plants are sold.  The crowns are developed roots from plants that have already been started, then dug up after the stalks have died back for the winter.  You will often find them available for sale in late winter and early spring, depending on the seasonal conditions where you live.  Seeds are not common as they won’t be “true to type”, meaning that you won’t necessarily get the same type of plant from the seeds as you had from the parent plant that produced them.

Before planting your crowns, you’ll want to carefully select the site and prepare the ground.  Give your asparagus loose soil that is rich in organic material by digging a 6 – 12 inch deep hole or trench and filling it in with quality compost and soil.  Follow the directions that come with your crowns as to how deep they should be placed, and how far apart, in the soil.  Usually planting depth is not far down, but you want a deep, enriched soil to allow new roots a chance to easily penetrate.  Also, plants need a lot of space since the crown will expand over time as the plant matures.

Asparagus do not tolerate competition from other plants like weeds very well, so be sure to keep the area weeded and mulched.  Do the weeding by hand, though, as the roots are shallow and using something like a hoe will damage them.  Though asparagus need consistent moisture, you also don’t want them waterlogged which can allow rot to occur, so ensure that the soil is damp but not soaking or with standing water.  The shallow roots are also problematic if you live in a cold zone, so you will need to heavily mulch the ground to protect them from freezing.

Most varieties of asparagus prefer cooler climates, but some will tolerate up to zone 9 conditions.  Though they do best in full sun, some morning or afternoon shade can be helpful for plants during hot summers.

Harvesting:

Asparagus is ready for harvest in the spring, but here’s the catch: you don’t want to harvest any for at least 2 – 3 years after planting.  Patience!!!  It’s hard, I know.  Asparagus stalks are the stems and leaves of the plant and they are harvested before those leaves open up.  Those leaves are responsible for carrying out photosynthesis, which is where a plant gets its food energy.  If you harvest too early in the plant’s life, or for too long in the season, the plant has reduced opportunity to gather energy that it will store in those roots for the next season.  This will stunt the plant’s growth, maybe even kill it, and that will put a damper on your fun, now won’t it?!

Once your plants are well established, you can harvest the stalks starting from when they first appear and for another few weeks.  Cut them at the soil level when they are about 7 inches tall but not after the frond-like leaves have started to unfurl (the stalks will be very tough by then).  As you continue to harvest, you will notice that the stalks will be thinner and that will be your cue to stop cutting and to let the plant gather energy for the roots.

The fronds will grow up to four feet tall or more and may also flop over.  Don’t worry about staking them as they are so wispy that it’s not worth the bother.  Female plants will start to produce flower stalks during the summer.  The flowers are barely noticeable, and regular removal of those flowering stalks will help to redirect energy away from fruit (which you don’t want to eat) and seed production back to the roots.  More energy to the roots will mean more and larger stalks to harvest the next spring.

Pests:

If it tastes good to you, it will taste good to other creatures, too.  Snails, slugs, asparagus beetles, and any other critter that likes to chew on tender, leafy material are going to be problems for your crops.  Be sure to pay attention to signs of plants being chewed on and take measures to remove or treat for pests.  If the plants are excessively damaged for too long, it prevents them from storing energy for the following year, and can leave them susceptible to disease.

Fusarium rot and other fungal diseases affecting roots are another concern.  Having well draining soil and not over watering will help lower the risk for these problems.  Also, creating an environment that fosters healthy growth and not over-harvesting will promote stronger plants that are more resistant.

Plant Summary:

• Perennial: Plants will live for several years, 15 – 30, depending on type and conditions
• Deciduous: fronds die back during late summer to early fall
• Height: up to 4 – 5 feet
• Width: up to 1 foot, though fronds may flop over
• Sun: full sun, will take some morning or afternoon shade in hot areas
• Water: regularly, do not let soil get dry
• Soil pH: neutral to slightly acidic
• Soil type: amend heavy clay or loose sandy soil
• Key nutrients: nitrogen for stalk development and phosphorus for strong roots, as needed
• Planting time: late winter to early spring, or as soon as they become available in your area
• Zones: 4-9, depending on variety