Planting asparagus is probably one of the best investments a vegetable gardener can make. Because it takes a couple of years before it can be harvested, it starts out as a crop for the patient gardener, but after that, it is ideal for the impatient gardener as it pops out of the ground almost overnight, sweet and tender and ready for dinner.
Asparagus, a hardy member of the lily family, is one of the few perennial vegetables. A sunny spot, lots of room (12 plants per asparagus lover), a dormant period, well-draining and very amended soil dug deep to at least 18 inches will foster the strong roots plants need to harvest.
Plant asparagus roots, referred to as crowns, in a trench or individual holes. Asparagus roots are long and white and hang like the tentacles of an octopus and should be fresh and firm. Untangle the roots as best you can and spread them over a mound of compost with the center of the crown facing upward. They should be spaced 18 inches from center to center, but if your soil is rich, reduce it to 12 inches.
Plant here in early spring when the ground is workable and the crowns are dormant. As long as the crowns are covered with about 3 inches of soil, they won’t suffer in a freeze. The depth for planting the crowns is variety and method dependent. The deeper method is to dig down a good foot, add a couple of inches of compost for under the crown and then create the mound. At this point, the top of the mound is about 6 inches below the soil surface. The shallower method is to plant just 3 or 4 inches deep and add a few inches of new soil to the top of the bed every other spring. Asparagus roots tend to rise to the surface of the soil over time, and what you are trying to do is keep the asparagus growing at the right depth — optimally 6 to 8 inches. Too shallow yields spindly spears, and too deep produces fewer and larger ones. Either way, once planted, fill with about 3 inches of soil, water well, and as the spears grow, keep filling soil to the surface.
In a few weeks, asparagus will start sending up tiny spindly spears, but do not cut them. They will quickly sprout into tall, ferny foliage. For the first summer, just weed and water. By the second summer, the spears will be considerably fatter and tempting to cut, but do so very sparingly, if at all. Any spear you harvest will not develop into foliage, and it is this foliage that feeds and strengthens the roots. Indulge yourself a little in year three, and by year five you can harvest for about six to eight weeks before you need to stop and let the remaining spears turn into foliage. In fall as the ferns turn yellow, they continue to feed the roots, so cut them as late as possible.
The vegetable is amazingly productive. Nothing you grow will ever give you as good a return as asparagus, and since a bed of asparagus will produce for decades, the time lag between planting and first harvest is rewarded by years of savory feasting.
Jane McLeod is a master gardener through the Colorado State University Extension. Call 970-879-0825 with questions.