Planting asparagus facts
- Hardiness: Hardy perennial can withstand winters with protection in colder areas; should be mulched in autumn.
- Planting: One-year crowns (vegetative propagation) in early spring. Can also be started from seed. Full sun requires direct light at least 6 hours/day; prefers 8 - 10 hours/day.
- Days to maturity: Begin harvesting lightly in years 2 and 3.
- Spacing: 18" in-row x 4' to 5' between rows; or in wide beds of three rows with plants 18 inches apart in all directions.
- Fertilizer needs: Medium-high requirement for nutrients, either from soil organic matter or fertilizers. Add organic matter prior to planting; apply nitrogen each year in early spring; side-dress after harvest; benefits from yearly top-dressing of compost. Refer to Fertilizing Vegetables for details.
- Approximate yield (per 10-foot row): 3 to 4 pounds/year.
Growing and care of asparagus
Asparagus is a perennial vegetable that lives from 12 to 15 years or longer. It is one of the most valuable of the early vegetables and is well adapted to freezer storage. During the harvest period, the spears develop daily from underground crowns.
Recommendation for planting a new asparagus bed
- Select all-male hybrid varieties. They are more productive and disease-resistant than older varieties;
- Start asparagus either from seed or from one to two-year-old crowns. Crowns are usually shipped and set out in March or April;
- Starting plants from seed requires an extra year before harvest. They are slow to germinate and should be transplanted in June;
- Purchased roots and crowns should be full and slightly moist; not shriveled. Roots that are dry brown or soggy black indicate poor storage and will probably give poor results;
- Check crowns for signs of viable buds. Inspect plants for signs of insects or disease; and
- Once you have the plants, keep the roots moist (but not soaking wet) by misting occasionally, and do not allow them to freeze or dry out. If it is necessary to keep the crowns for more than a few days, store them in a cool place or heel them in a trench of moist soil in a shaded location
- Choose a site with good drainage and full sun. The tall ferns of asparagus may shade other plants, so plan accordingly. Prepare the bed as early as possible and enrich it with compost.
- Traditionally, asparagus crowns are set in a trench 12-inches deep and 12- to 18-inches wide, with 4 to 5 feet between trenches. But many gardeners are successful in placing crowns in the bottom of a 6-inch trench. Crowns should be spaced 15 to 18 inches apart and raised slightly above the roots. Remove any rotted roots before planting. Spread the roots out over a 2-inch mound of soil at the bottom of the trench and cover the crown completely with soil. Firm well and keep the bed well watered.
- Weed the bed each spring before the first shoots come up, to avoid accidentally breaking off spears. During the production period, it is best to pull weeds rather than use a hoe.
- Asparagus shoots or spears should not be harvested the first season after crowns are set. Harvest lightly for 3 to 4 weeks the second year. The fleshy root system needs to develop and store food reserves for subsequent seasons. Plants harvested too heavily too soon often become weak and spindly.
- For asparagus started from seed, do not harvest at all the first two seasons, and harvest lightly the third. When the asparagus plants are in their fourth season, harvest for 8 to 10 weeks per year.
- Harvest spears daily during the harvest period. The 6- to 8-inch spears should be snapped off just below the soil surface. If the asparagus is allowed to get much taller, the bases of the spears will be tough and will have to be cut. Cutting too deeply can injure the crown buds, which produce the next spears. To blanch (whiten) the spears, mound soil around them, or otherwise exclude light so they do not form chlorophyll in the stalks.
- Allow the spears to grow once the harvest is over (after 8 to 10 weeks). Some gardeners prefer to support the growing foliage with stakes and strings to keep the bed tidy. In high-wind areas, it is a good idea to plant the rows parallel to the prevailing winds so that the plants support each other to some extent.
There are several ways to extend the harvest period
- Plant at different depths (4”, 6”, 8”, 10”). The shallower plantings will come up first and can be harvested while the deeper plantings are just forming. This method will result in a slightly longer harvest, but the plants may be less vigorous.
- Remove mulch from half of the asparagus bed and leave mulch on the other half. The exposed soils will warm up more quickly, and the crowns will sprout earlier. Remove mulch from the second bed when spears begin to appear.
- Plant double the amount of asparagus needed for your household. Harvest half of the plants as you normally would in spring and early summer and allow the ferns to grow in the other half of the asparagus planting. Then, cut the ferns in the un-harvested plot in late July. The crowns will send up new spears, which can be harvested till late in the season. Keep plants well-watered. A light mulch will aid in spear emergence. When using this method, harvest the spring bed only in spring and the fall bed only in fall. Otherwise, you risk weakening the crowns.
Winter care of asparagus
In all asparagus plantings, cut the foliage down to 2-inch stubs after frost when the foliage yellows, and before the red berries fall off (all-male hybrids don’t produce berries). A 4- to 6- inch mulch will help control weeds and add organic matter and nutrients.
- Process or refrigerate immediately in a mesh or plastic bag.