Spear into Spring with Asparagus
Several years ago, I was informed by my wife that we were going to plant asparagus. My response was: what are we going to do with asparagus? I was gently informed by my gourmet wife that asparagus was a very versatile vegetable, that it can be steamed, sautéed, roasted, grilled, stir-fried, featured in a salad or soup, or even eaten raw; in other words, the possibilities are endless. In addition, it is one of the earliest spring vegetables, and it would be nice to have something fresh from the garden in the spring. Naturally I concurred with my wife, and suggested that she order some seeds and we would plant them in the garden where we had planted corn the prior year.
But my wife’s response to my seed-purchasing proposal was “That dog isn’t going to hunt” — because asparagus is a perennial, and once planted, it can keep producing for 15 years or longer. Well, so much for that brilliant idea of crop rotation. I needed to find a permanent location for the asparagus. After thinking for a moment, I came up with the perfect location — a spot on the northwest corner of the lawn that was out of the way, and most importantly, it would cut out a little lawn-mowing. Perfect! Well, not exactly. When I proudly informed my wife of my proposed location, she got that look — you know the one — like when you go shopping and you are wondering if you left the oven on. I can still hear her words: “Incredible, under the oak tree … and where you got the mower stuck last spring…” plus a few other dangling modifiers that I didn’t care to catch. So on that high note, I figured I had better do a little research before offering any additional suggestions. Following is a summation of my remarkable asparagus horticulture journey.
The most critical decision a gardener must make, once he or she decides to grow asparagus, is site location, because, as I mentioned, asparagus is a perennial, so the site should be thought of as a permanent location. Like most vegetables, asparagus will not tolerate wet soggy soil. Select a site that receives full sun and that is well-drained or use a raised bed.
Okay, but how do I know if the location is too wet? Well, after a rainfall, if water stands in the spot selected for more than an hour, it’s probably too wet for asparagus.
The bed should be prepared as early as possible by amending the soil with organic matter such as manure and compost. A soil test should be performed, as asparagus does poorly in soil with a low pH (high acid); the Virginia Cooperative Extension recommends a pH range of 6.0-6.7. https://pubs.ext.vt.edu/426/426-401/426-401.html However, some researchers suggest an even less acidic, higher pH, because fungal diseases that contribute to asparagus decline — Fusarium crown and root rot — survive better in more acidic soil. Increasing the soil pH level to 7.0-7.5 reduces the survivability of Fusarium. For additional information on pH levels for asparagus, take a look at http://www.pubs.ext.vt.edu/AREC/AREC-66/5-specific-commodity-recom.pdf The higher pH level does not appear to affect the productivity level of asparagus, only the fungal diseases.
Good soil build-up is important with asparagus. We only get one chance — and that’s before planting — to adjust soil root-zone depth to 12-18 inches. If this opportunity is missed, it becomes very difficult to move nutrients deeper into the soil without disturbing and damaging the roots.
Asparagus may be planted 4-6 weeks before the final spring frost, which historically in our area is the last week in April.
Although it is possible to grow asparagus from seed, most home gardeners prefer to plant one-year old crowns because of the additional time and maintenance required to grow asparagus from seed. For additional information on how to grow asparagus, see VCE Publication No. 426-401, https://pubs.ext.vt.edu/426/426-401/426-401.html
For asparagus beginners, the second critical decision is what variety to select. There are two major categories to choose from:
1. open-pollination varieties, which include Mary Washington and Martha Washington, or
2. all-male hybrid varieties, such as Jersey Knight and Jersey King.
Asparagus is a dioecious plant, which is just a fancy way of saying that there are both boy plants and girl plants; thus, male and female flowers are produced on separate plants. The flowers on male plants are small, bell-shaped, whitish-green and more conspicuous than female flowers. Following pollination of the female flowers by bees, a round berry containing one to eight seeds is formed and turns red at maturity.
In the late 1800’s, Professor William J. Green, a horticulturist at the Ohio State Research Station, discovered that male asparagus plants are about 50% more productive than female plants. I’m not making this up! More information about Professor Green’s research and about early 1900’s growing techniques can be found at http://www.gutenberg.org/files/31643/31643-h/31643-h.htm.
One of the conclusions that Professor Green made was that the lower productivity of female plants is the result of energy allocated to seed production. The fruit produced by the female plant competes with the crown and roots for nutrients. Since asparagus is a perennial, the plant depends on the nutrients stored in the crown and root for next year’s spear production; therefore, the female plant is storing up less energy in the form of sugar and nutrients, resulting in lower yields than their male counterparts. For additional information about the advantages of male asparagus plants, see http://aesop.rutgers.edu/~asparagus/program/male.html
Being something of a history buff, I wanted to find out a little about when and how the male hybrid plants were developed. In the 1980’s Rutgers University began releasing what are called “supermale” hybrids developed by Dr Howard Ellison, a horticulturist at Rutgers University. Dr Ellison is regarded as the pioneer in the breeding of the supermale plant. A brief overview of Dr. Ellison’s work may be found at http://vegnet.osu.edu/sites/vegnet/files/imce/Asparagus trial.pdf
After reviewing the attributes of the hybrid male asparagus plants versus the open-pollinated plants, I elected to go with the all-male hybrid plants. A visit to the VCE web site at https://pubs.ext.vt.edu/426/426-480/426-480.html suggested two varieties for our area: Jersey Knight F1 and Jersey Giant. I selected Jersey Knight F1 to plant.
Next, I identified a dry, well-drained location, amended the soil with organic matter, and planted and covered the crowns. Here’s where patience comes in handy. I needed to wait until the second spring after planting to harvest any spears. The first harvest should be not more than 2 or 3 spears per plant. But patience paid off. Nowadays, I harvest young spears for a period of 4 to 8 weeks.
Is it “OAD” (one and done)? Well, not quite. Asparagus is a poor competitor with weeds; therefore, in order to have a successful asparagus bed, I needed to maintain the asparagus bed by keeping it as weed-free as possible. I accomplished this task by hand-weeding and very light cultivation with a hoe; I avoid the use of a tiller or digging deep to avoid damaging the crowns. Organic mulches such as “weed free” grass clippings, leaf mulch, wood chips, “clean” straw or compost can be applied up to 2-3 inches deep to suppress weeds. Weed-free grass clippings and clean straw? No, I elected to use leaf mulch mixed with wood chips. I recall being told by an elder Madison County gardener to use common rock salt as a weed control because asparagus, being deep-rooted, can tolerate some salt, but I elected not to follow this advice because salt can damage soil structure by creating a crust that impedes water infiltration. In twenty years or so, when it comes time to start another asparagus bed at a different location, what would I plant in the old location with its salty soil?
Asparagus plants are heavy feeders, meaning they require a lot of nutrients, so every 2-3 years I take a soil sample and send it off to the Virginia Tech soil lab to determine any nutrient deficiencies or pH adjustments that may be needed.
Now each spring when I go out to harvest those first asparagus spears, I think back on my amazing journey with asparagus. Sometimes I pause to imagine the reaction of our colonial ancestors when they walked out to the garden and found those first green spears after a long winter without fresh vegetables. No wonder asparagus was one of the first vegetables brought to this country by our forefathers.