Asparagus Planting Among Trees

Q. I put in a lot of effort into planting asparagus. I have a large planted area but no asparagus! I planted Mary Washington this year and many times in the past, but I have had no luck. Are the trees nearby this area competing with them too much?   

Asparagus trials in 2008. About 15 varieties of asparagus were trialed in the Mojave Desert and evaluated by chefs for quality. All 15 performed well but those bred for the hot desert could be harvested for a longer period of time.

A. There is a lot to cover regarding asparagus growing here. First, there is no problem planting asparagus among trees if there is room. I will post a primer on growing asparagus in the Mojave Desert in here.

Make Sure There is Room for It

Asparagus gets 5 feet tall after harvesting the spears so make sure it has room to grow to that height. I have had asparagus planted among fruit trees, as well as alone in rows, since 1996. I planted asparagus in 2019 and they are coming up nicely. This is a great climate for asparagus if it’s planted and managed correctly.

Sometimes you will see advice to "snap" the spears off instead of cutting them. I tired it and don't like it. The remaining stubs above ground interferes with operations. I prefer to cut them about one inch below ground with a sharp knife or asparagus knife.

Just make sure the asparagus gets at least 8 hours of sunlight.

Variety Trials

            I have grown about 15 varieties of asparagus for comparison purposes in our Mojave Desert climate. They have all done well but there are some differences among the varieties. Stay away from heirloom varieties such as Mary Washington because they don’t produce enough spears in any climate. There is nothing remarkable about them.

I trialed a purple variety called Purple Passion years back and liked it. The spears were sweeter but the variety didnt produce as many spears as UC157. Choose improved varieties over the old standbys like Mary Washington. I prefer the UC varieties over Rutgers Jersey line.

            Expect an asparagus bed to last about 20 – 25 years if managed correctly. They do well with drip irrigation. I would use drip tubing with emitters spaced about 12 inches apart or plant them in containers for small spaces. In rows using drip tubing, plant in a triangular pattern so that crowns are 12 to 18 inches apart on either side.

Asparagus grows well with drip irrigation. Make sure you find a balance between soil moisture and drainage. If the soil is too wet, the roots will rot. If the soil is too dry, they don't produce well.

Asparagus Loves Manure or Compost Applications

            Asparagus loves rich soil and water but they also like their roots and crowns to “breathe”. Mix with desert soil an equal volume of rich compost at the time of planting about 12 inches deep. Buy two or three-year-old, all-male crowns and plant them 8 to 10 inches deep. Make sure the soil in the asparagus bed is free of any rocks or they will produce crooked spears.

Asparagus spear emergence in early spring after a rich compost application.

Asparagus Must Have Water Drainage

            The soil must drain water easily in a few hours after an irrigation. Irrigate thoroughly after planting but don’t irrigate again until the soil is slightly moist at 6 inches deep. If you’re not sure about when and how much to irrigate, follow my blog, Xtremehorticulture of the Desert, my YouTube video or podcast on how to irrigate. If watered too often, asparagus roots and crowns will suffocate and rot.

Differences in Varieties

            Plant ‘UC 157’ developed by the University of California for the hot desert and plant them from mid-January to early February. Stay away from planting by seed unless you are an experienced gardener. If you want some variation in spear colors, mix in a variety called ‘Purple Passion’ but keep in mind they don’t produce as many spears as UC 157, but they are sweeter to the taste.

Abnormalities do occur like fasciation but they are rare.

Don't Forget to Fertilize

            Each year, before the beginning of the growing season just after the Christmas holidays, apply about 1 inch of rich compost on top of the soil above the crowns and water it in. If the soil has plenty of organics in it already, then use a mineral fertilizer such as 16 – 16 – 16 in early spring.