How to Grow Asparagus From Seed
You can start asparagus from seed, but germination is slow (four weeks or more), and weeds are difficult to control in young seedlings.
Young domesticated asparagus can not compete with other plants, in particular weeds.
Plants grown from seed indoors can be transplanted -the following spring -to a permanent location.
How to Grow Asparagus From Crowns
It is more advisable to start from "crowns". Choose large, one-year-old crowns if possible. They transplant easier, produce plants as vigorous as two-year-old crowns and are less expensive.
Site Selection is critical for asparagus . Select an area that is free of perennial weeds .
Asparagus prefers a loamy soil that is well drained. If possible start to prepare a site 1 year in advance of planting by turning the soil and adding compost. Soil pH should be 6.0 -8.0 and be sure there is plenty of well rotted organic matter present.
Dig a trench roughly one foot deep and one foot wide. Mix garden soil, compost and fertilizer and shape it into a small mound in the trench center. Set the asparagus crown atop the trench - buds upward, and drape its roots over and around the sides of the mound. The crowns top should be about halfway down in the trench - which is 6" below the soil surface.
Cover the roots with garden soil up to the crown and water vigorously - I didn't say drown it - just well watered. As shoots pop up, add more soil and modest amounts of compost until the trench is level with the soil surface.
Asparagus crowns should be spaced 16 inches to 18 inches apart in the trench row. When you want more than one row, space rows 4 feet to 6 feet apart.
Do not compact the soil over the newly filled trench or the emergence of the asparagus will be severely reduced.
Spears should emerge within one week in moist soils. By mid-season of the planting year, a ridge forms that is 4 inches to 6 inches high and 2 feet wide over the asparagus crowns. Maintain this ridge for the duration of the planting.
If perennial weeds or grasses infest an asparagus bed it is extremely difficult to reclaim it. So keep the asparagus bed well-mulched , using shredded leaves or straw. Weed frequently and carefully, asparagus roots near the surface are easily damaged. Domesticated Asparagus does not compete well with weeds or even other domestic garden plants, do not interplant with other crops.
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Asparagus fares well with tomatoes. The tomato plant repels the asparagus beetles, Meanwhile, asparagus is believed to repel many harmful root nematodes that affect tomato and related plants. Do not interplant them, but a close proximity is helpful.
Moisture during the summer is critical to keep the plants healthy because next year's crop is directly related to health of the fern growth after the spears have been harvested in the present year. Asparagus is very drought tolerant and will generally survive without supplemental watering. It seeks moisture deep in the soil. However, if rainfall is insufficient when planting or afterwards, it is beneficial to irrigate the crowns. Otherwise the plants will become stressed and growth will be impeded.The incidence of disease can be reduced by proper spacing and by watering early in the day so leaves dry quickly or by using soaker hoses. Inexpensive water timers are available.
Control weeds by hand-pulling or shallow cultivation to avoid injury to the plant roots. In a small planting, it's more practical to control weeds through shallow cultivation by hoeing. Using an organic mulch such as grass clippings or shredded bark that has not been treated with a herbicide also helps control weeds.
If perennial grasses and broad leaf weeds have gotten out of control, use glyphosate , sold under the trade name 'Roundup' and 'Weed stop', before spears emerge in the spring. During harvest keep cultivation shallow to prevent damaging the spears that have emerged.
Organic mulches may also be used to inhibit weeds.
Common table salt once was used to control weeds in asparagus. But is no longer recommended. Although asparagus is more tolerant of high salt levels in the soil than most plants, the sodium in table salt can permanently destroy the soil structure.
Asparagus remains in place for decades, pre-planting soil preparation helps future productivity tremendously. Working compost, manure, and other organic materials into the bed well in advance of planting is a good idea.
Fertilize annually . Immediately after harvest apply about 2 pounds of a 5-10-10 fertilizer per 100 square feet , or spread well rotted manure, or Liquid Fish Concentrate over the bed. You can also add additional well-rotted manure or compost in late fall.
Lime and fertilizer applications are best based on a soil test, which is not always feasible. In general, two pounds each of actual nitrogen, phosphorus (P2O5), and potash (K2O) per 1,000 square feet of garden space is adequate. Checking soil pH is not as vital for Asparagus as it is for other garden plants, grows in just about any soil. Optimal pH is anywhere from 6.0- 8.0
Asparagus Beetle Cut Worms Thrips
Asparagus Aphid Asparagus Miner
Do not harvest asparagus the first season after planting crowns, It takes at least two years and sometimes up to three years to establish an asparagus patch. It can be harvested for a short time (not to exceed two weeks) the second year. Puny plants and small spears result from excessive harvesting , and early harvesting. The second year after planting the crowns, harvest asparagus from 6 to 8 weeks annually. Weak plants should either not be harvested or harvested for less time.
Exercise care in cutting the spears to prevent damage to those spears that have not yet emerged. Cut or snap the spears at ground level. This practice eliminates the possibility of damaging other spears.
The diameter of an asparagus spear has no relation to its quality. Spears average 5" to 7" high at their peak quality and before the tips start to loosen. When the tips loosen, the spears become woody and taste is undesirable.