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Asparagus
Expert guides on every fertilizer we carry, step-by-step crop growing instructions, and the science behind healthy soil.
Crop Overview
Asparagus is a long-lived perennial that can produce for 15-20 years or more when properly fertilized and maintained, making initial soil preparation and ongoing nutrition critically important investments. Unlike annual vegetables, asparagus builds energy reserves in its massive root crown system throughout the growing season, then deploys those reserves the following spring to push up the edible spears. This unique growth cycle means fertilization strategy must support both the current harvest and next year's production simultaneously. Phosphorus is especially important at planting since the deep root system (roots can reach 5-6 feet deep) is difficult to amend after establishment. The most common fertilization mistake is neglecting the fern stage — after harvest ends in late June, the plants grow tall feathery fronds that photosynthesize and store energy in the crowns. Fertilizing heavily during this fern growth stage directly increases next spring's spear production. Asparagus also has an unusually high tolerance for salt and prefers slightly alkaline soil, which sets it apart from most vegetables. Annual topdressing with well-rotted manure or balanced fertilizer in early spring before spears emerge and again after harvest ends ensures consistent production year after year.
How to Apply ?
Seedling
Incorporate generous amounts of phosphorus (bone meal or superphosphate) and compost into the trench at planting depth of 6-8 inches to support the deep root crown development critical for long-term productivity.
Vegetative
After harvest ceases in late June, apply balanced fertilizer (10-10-10 or 10-20-10) at 2 lbs per 100 sq ft to fuel the fern growth that stores energy in crowns for next year's spears.
Flowering
Female plants will flower and set red berries on the ferns; maintain consistent nutrition but consider removing berries to redirect energy to the crown rather than seed production.
Fruiting
N/A — asparagus spears are harvested before the reproductive stage; the edible portion is the emerging shoot, not a fruit.
Common Mistakes
Neglecting fertilization after harvest when the fern growth stage is the most critical feeding period|Failing to deeply incorporate phosphorus at planting which cannot be corrected later|Harvesting spears for too many weeks the first years without allowing crown energy recovery|Using high-nitrogen fertilizer exclusively when asparagus needs balanced nutrition for crown storage|Not maintaining adequate soil pH leading to poor nutrient uptake in acidic New England soils
Organic Options
Wicked Organics All-Purpose Blend supplemented with generous compost topdressing provides excellent results. Apply well-rotted manure (2-3 inch layer) in fall as both fertilizer and winter mulch, and use fish emulsion during the fern growth stage for a quick nitrogen boost.
Nutrient Deficiency Signs
Nitrogen
Spears emerge thin and spindly in spring, fern growth is sparse and pale yellow-green rather than vigorous dark green, and overall crown vigor declines year over year.
Phosphorus
Spears are thin with purplish discoloration, root crown development is poor in new plantings, and fern growth is stunted with dark blue-green coloring on older fronds.
Potassium
Fern tips turn brown and die back prematurely in late summer, spear quality declines with tough woody texture, and crowns show reduced winter hardiness.