Asparagus – Gardening Tips from the Culinary View
as recommended by Michael Vidrine
To say that winters in our area can be variable is a bit of an understatement. Most of our winters are relatively mild with an occasional good freeze or three. Other winters, there are hardly any freezes at all. But every now and again, Mother Nature brings us a winter more appropriate for the Dakota’s and we learn what plants can really survive here. Regardless which variety of winter we have gotten, along about mid February to early March, our asparagus have had enough of their dormant napping and decide to pop up and take a look around.
Our garden asparagus, Asparagus officinalis, is an herbaceous perennial plant that in a good location can live for 15 to 25 years. Records indicate that asparagus has been cultivated for over 2000 years and is thought to be native to much of Europe and adjacent parts of Asia. The plants were first brought by colonists to the America’s in the 1600’s. Asparagus plants are usually dioecious with male and female flowers on separate plants. The female plants produce a small berry which our birds really like and will spread seeds throughout the area sometimes resulting in asparagus seedlings becoming a bit of a weed nuisance. Interestingly, even though the plant is edible, the berry is poisonous to humans. This is the opposite of the tomato where the plant is poisonous but the fruit (tomato) is yummy. The part of the asparagus we eat is the stem shoot which sprouts from the below ground root crown. The shoots have to be harvested while young and tender before they become too long and tough. The thickness of the stems tend to indicate the age and healthiness of the plants with more mature plants producing thicker stems. The stems do not get thicker once emerged – only longer.
Asparagus shoots can be green or purple depending on variety. White asparagus are produced by continually covering shoots with soil or mulch as they emerge so they grow in the dark and don’t develop chlorophyll.
Since asparagus is a long lived perennial, the garden site should be chosen with care and well prepared before planting. Asparagus prefers deep well drained soil and full sun. Starting with clean weed free soil will help to reduce a lot of weeding down the road. Mulching the bed when the plants are dormant also helps improve the soil and reduce weed pressure. Given our water quality, it’s nice to know that asparagus can tolerate moderately high pH and salt. Asparagus can also be grown in a landscape bed and the mature ferny looking fronds make a nice backdrop with shorter plants in front. Keep in mind that the mature plants can get over 6 feet tall.
Asparagus is not particularly difficult to grow but requires a bit of both perseverance and restraint. Perseverance because it takes a few years to get to a significant harvest and restraint because it is important to know when to stop harvesting. Asparagus can be grown from seeds but will take a number of years before being mature enough to harvest. Most often, one to two year old asparagus crowns – the root base of the plant – are planted to speed things along. The crowns should be planted 6 to 12 inches deep – deeper in light sandy soils and more shallow in heavy clay soils and about 1 foot apart. Many gardeners lightly cover the crowns in a trench and gradually fill the trench in as the shoots emerge. I’ve had pretty good luck planting the crowns at the appropriate depth and covering them all at once – this approach works when the soil is really high quality with plenty of organic matter. If in doubt, the gradual covering is always a safe bet. Crowns are usually available for planting in mid to late winter. Many sites recommend about 100 square feet of planting for a family of 4. Our current planting is 100 square feet and my wife and I pretty well eat all that by ourselves – but we really like asparagus. One more caution about site selection – mature asparagus are terribly difficult to dig up and move. We had asparagus in our regular vegetable garden and my wife (the primary harvester) fussed about always getting asparagus fern debris is her hair while picking adjacent vegetables. She threatened to retire from vegetable harvesting so I immediately began digging. One 20 foot raised bed of asparagus took me two days to hand dig. I learned my lesson and hope to save you from the toil. Our asparagus is now in a dedicated 50 foot raised bed – half asparagus and half artichokes.
A light harvest can usually be taken from 3 year old asparagus plants. As plants gain maturity, the harvest gets heavier and longer. Asparagus shoots grow extraordinarily fast and harvesting may need to be done daily or every other day. Cut asparagus shoots at or just below the soil level – don’t go too deep or you may damage new shoots or the crown. Some gardeners also just snap the stems off without cutting. Remember you are removing the stems of the plants and at some point you must stop harvesting and let the plant go to full maturity and replenish itself. As plants become stressed from harvesting, the shoots will begin to become more thin and spindly – a sign it’s time to stop harvesting. Asparagus are pretty heavy feeders and respond to regular fertilization. Nitrogen in particular will be needed every year – other nutrients as indicated by a soil test. Asparagus will almost always need supplemental watering in our area and a drip system is a good way to go as hand watering a large planting will get pretty tedious.
Asparagus varieties suggested for our area include Martha Washington – an heirloom variety, UC 157 – a hybrid developed by the University of California , Purple Passion if you want to try a purple variety and the predominantly male varieties Jersey Giant, Jersey Knight, and Jersey Supreme. Male plants tend to be a bit more vigorous with larger stems. Mostly male plants also mean less fruit production and less surprise asparagus seedlings.
In the late fall – especially if we get a good freeze, the asparagus fronds will begin going dormant. In colder locations – like when we lived in zone 6 – we would push the fronds on to the ground forming a layer of fluffy mulch that would hold snow and ice throughout the winter and help protect the crowns. With our generally mild winters here, it is best to cut and remove the fronds once they are mostly dormant and then apply a generous layer of mulch or compost to the bed. Removing the fronds in our mild climate helps to reduce any residual pathogens and pets.
Asparagus can have some disease and pest issues but our plantings have rarely needed any significant controls. The mature fronds sometimes attract stinkbugs and I will spray to knock them down because they are such a pest of so many other vegetables. The Aggie Horticulture website also has a lot of information on pest identification and controls.
Asparagus are at their absolute best fresh from the garden but can be stored in the refrigerator for 4 or 5 days by placing them base down in a container with an inch of water and covering with a plastic bag. If you have a large harvest, blanching and freezing is a long term storage option. I often eat asparagus raw right out of the garden – it’s a wonderful treat after a long winter. Besides eating them raw, asparagus spears can be steamed, roasted, stewed, grilled, fried and even pickled. Asparagus has a host of vitamins and minerals and lots of dietary fiber. It is filling but very low in calories … and it tastes good. If the asparagus has been harvested a bit mature, the bottom of the stem may need to be peeled if it is fibrous. Any tough trimmings or over mature stems are really good in a vegetable stock. We most often steam or roast our asparagus to just the tender crisp stage and sauce with just a bit of olive oil and parmesan or a bit of balsamic vinegar.
If you are unfamiliar with consuming asparagus, there is one common side effect that many people experience – asparagus tends to produce rather strong smelling urine. Asparagus contains asparagusic acid which can produce some volatile sulfur compounds in urine. It can be a little startling if you are not expecting it – as can pink urine after eating beets.
If you have a nice spot you can dedicate to a long term perennial crop, asparagus are relatively easy to grow and you will really enjoy those freshly harvested spears.
Brazos Valley Gardener, Orchardist, Apiarist and Instructor