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Growing asparagus in Kentucky

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By Dennis Morgeson

 

Asparagus is a long- lived perennial vegetable crop. Each plant can be productive for 15 or more years if given proper care. 

Asparagus will grow in most any soil as long as it has good drainage.  Asparagus doesn’t like to have wet feet, it leads to root rot. An ideal pH of 6.5 to 7.5 will give you good results; it will not tolerate a pH under 6.0. If you are thinking of planting asparagus, have a soil test done and the soil amended before planting. If you aren’t willing to test your soil, apply 10-20-10 or a similar fertilizer at a rate of 6 pounds per 1000 square feet; this can also be broadcast around established plants for added growing power.
Only buy one-year-old, healthy, disease-free crowns from a reputable grower. Asparagus is sold in crowns, which are one- year-old plants grown from seed. When fully established, each crown can produce one-half pound of asparagus spears. You can start your own asparagus from seed, but it will have to grow one year where you sow it. The following spring it will have to be dug and spaced out in its permanent location. This basically means you lose one year of spear production in your garden. Another disadvantage to planting asparagus by seed is getting the variety you want; the best varieties aren’t usually available in seed form.
When selecting a variety of asparagus, there are some interesting things to consider. There are new varieties on the market, which are far superior to the old varieties.  New all-male hybrid asparagus such as Jersey Giant, Jersey Prince, and Jersey Knight, do not produce seed. Basically, when asparagus seeds, the new plants become weeds that must be pulled out as to not overcrowd the bed.  Female plants expend a lot of energy making seeds and don’t produce as many edible spears as do the male plants. The new all -male asparagus varieties generally out produce the old Mary Washington varieties by 3 to 1.
Asparagus should be planted after the soil has warmed up to about 50 degrees, usually in April.  There is no advantage to planting it earlier because it won’t grow until the soil warms, and the longer it sets in cold wet soil, the more likely it is to rot. If you plant asparagus in the vegetable garden, plant it on the west or north side so it won’t shade the other vegetables.
When planting asparagus, dig a furrow no deeper than 5-6 inches, if you plant it any deeper overall yield will be reduced.  Apply 1 pound of 0-46-0 (triple super phosphate) or 2 pounds 0-20-0 (super phosphate) fertilizer per 50- foot of row in the bottom of the furrow before planting.  This will stimulate root growth and increase later yields.  Toss the crowns into the furrow on top of the fertilizer, it won’t burn the roots, and the plants will grow just fine regardless of how they land in the furrow. The crowns should be spaced 1-1/2 feet apart. If you plant more than one row, space them five feet apart.
After planting, back- fill the furrow to its original level. You don’t have to gradually fill the furrow, just make sure not to walk on it; this will pack the soil down. If the soil is warm and the asparagus is kept moist, it should emerge in a week or so after planting.
One important thing to remember is NOT to harvest the asparagus the first season. It will need all of its energy to produce a larger crown and store food for the following season. If we have a dry summer, keep it watered, especially the first year.  Generally, asparagus doesn’t need to be irrigated, however, if we have an exceptional drought, the following year’s harvest will be reduced if you don’t irrigate.
There aren’t many insect and disease problems on asparagus. The one real problem is asparagus beetles, which chew on the leaves and stems, causing them to turn brown.  This can reduce the yield the following season. Sevin will give good control of asparagus beetles; simply spray at the first signs of damage.
At the end of the growing season, don’t cut down the ferns. Leave them through the winter. They will help protect the root systems by catching snow and keep the soil moist and cool. By keeping the soil cool, the asparagus will be delayed and won’t be as likely to get frost damaged in the spring. Around the last of March, the old ferns can be mowed as low as possible.
I have always heard of people using salt for weed control in asparagus, but it’s really not necessary or a good idea as far as soil health goes. Salt will actually impede water infiltration into the soil and can leach into surrounding areas, killing other vegetables and plants that aren’t as salt tolerant. The first year, use a good layer of mulch for weed control, and it will also conserve moisture. You can also use labeled pre-emergent herbicides. If you have an old patch of asparagus, you can spray Round Up over the bed before the fronds emerge. This will kill any existing weeds; this is a good time to apply a layer of mulch. It’s a good idea to apply one-half pound of ammonium nitrate fertilizer per 50 feet of row each year when harvest is finished. This will increase shoot growth, which will increase food storage, which will increase harvest the following spring.              
Once you start harvesting asparagus, it can continue until 75 percent of the new spears emerging from the soil are less than 3/8 of an inch wide or about the width of a pencil. At this point, you should discontinue harvest. Asparagus should be harvested in the morning while it is freshest and stored in the refrigerator at 38-40 degrees. If you have any questions call me at the office at 859-336-7741.  Happy gardening.