Asparagus fertilizer (16-10-13) is a crop-specific granular blend engineered for the unique nutritional demands of perennial asparagus beds. Unlike annual vegetables, asparagus crowns remain in the ground for 15 to 20 years, making targeted nutrition critical for long-term productivity. This formula features higher nitrogen (16%) to fu...
Provides 16% nitrogen (from urea and polymer-coated urea for extended release) to fuel vigorous growth. The Purkote slow-release component feeds for 6-8 weeks per application, reducing the total number of applications needed per season.
P · Phosphorus
10%
Delivers 10% phosphorus (from monoammonium phosphate) to promote deep root development and support establishment of new plantings and perennial crowns
K · Potassium
13%
Supplies 13% potassium (from muriate of potash and potassium magnesium sulfate) to strengthen cell walls, improve disease resistance, and enhance winter hardiness
This 16-10-13 asparagus fertilizer is a custom-blended granular formula produced by Green Mountain Fertilizer specifically for asparagus cultivation. The nitrogen component comes from two sources: standard urea for immediate availability and Purkote (polymer-coated urea) for sustained release over 6-8 weeks. This dual-source approach prevents the boom-and-bust nitrogen cycle that can stress asparagus crowns, instead providing steady nutrition throughout the fern growth period when the plant is banking energy for next year's harvest.
Phosphorus is supplied by monoammonium phosphate (MAP), a highly water-soluble form that reaches asparagus roots quickly. Potassium comes from two complementary sources: muriate of potash for concentrated K₂O delivery, and potassium magnesium sulfate (langbeinite) which simultaneously provides potassium, magnesium, and sulfur. The 7% calcium supports cell wall integrity and helps maintain the slightly alkaline soil pH (6.5-7.5) that asparagus prefers.
This formula is optimized for asparagus but also benefits other perennial edibles with similar nutritional profiles. Rhubarb shares asparagus's need for high nitrogen to fuel large leaf production and crown storage. Artichokes are heavy-feeding perennials that respond to balanced NPK with calcium and magnesium. The extended-release nitrogen makes this formula suitable for any perennial crop that benefits from sustained feeding.
Application Rates
How Much to Use
Garden & beds
0.5-1 lb per 100 sq ft at pre-planting; 0.25-0.5 lbs per 100 sq ft for established beds in spring and post-harvest
Lawn
N/A — crop-specific fertilizer formulated for asparagus beds, not turf
Trees & shrubs
N/A — not formulated for tree application
Containers
1-2 teaspoons per plant, sprinkled 4-6 inches around the base
Frequency
2-3 times per growing season: early spring before active growth, mid-season to support continued production, and optionally late summer at half rate if soil tests indicate depletion
Step by Step
How to Apply
1
Soil Test
Test your soil before the growing season to confirm nutrient needs and pH. Asparagus prefers pH 6.5–7.5.
2
New Bed Rate
For new beds, work 0.5–1 lb per 100 sq ft into the top 6–8 inches of soil before planting crowns.
3
Established Bed Rate
For established beds, broadcast 0.25–0.5 lbs per 100 sq ft in early spring before spears emerge.
4
Post-Harvest Application
Apply a second application immediately after harvest ends (late June/early July) to support fern growth and root energy storage.
5
Even Spread
Spread evenly over the bed surface, avoiding direct contact with crowns which can cause burn.
6
Water In
Water thoroughly after each application to move nutrients into the deep root zone.
7
Dormancy Warning
Do not apply during fall or winter dormancy. Asparagus does not actively take up nutrients when dormant.
Asparagus nutrition revolves around two critical windows: pre-harvest in spring and post-harvest in summer. In early spring, before the first spears emerge, broadcast 0.25-0.5 lbs per 100 sq ft evenly over the entire bed. After your last harvest (typically late June), apply a second feeding at the same rate—this post-harvest application fuels the fern growth that creates and stores carbohydrates in the crown for next spring's crop. For new plantings, incorporate 0.5-1 lb per 100 sq ft into the soil before setting crowns. Do not harvest spears during the first two years. For commercial acreage, apply 100-200 lbs per acre split between pre- and post-harvest applications.
See It In Action
Watch
Handling & Timing
Safety & Season
Safety & Storage
Wear protective gloves and eye protection during handling. Avoid breathing dust—use a NIOSH-approved dust respirator if applying in windy conditions. Wash hands thoroughly after handling. Store in a cool, dry, well-ventilated area protected from weather. Slightly reactive with oxidizing agents, metals, alkalis, and moisture—keep sealed when not in use. Prevent entry to sewers and surface waters. Keep out of reach of children and pets.
Seasonal Notes
Spring: Primary application window. Apply before spear emergence when soil becomes workable. Summer: Apply immediately after final harvest (late June/July) to fuel fern growth and crown energy storage. Optional half-rate in August if ferns appear pale. Fall: Do not apply. Allow ferns to naturally die back, then mow and mulch. Winter: No application. Plan soil testing for spring.
In Context
How It Compares
This 16-10-13 asparagus formula provides higher nitrogen than typical garden fertilizers like 10-10-10, which is important because asparagus is a nitrogen-hungry perennial. Compared to straight urea (46-0-0), this blend provides balanced NPK plus secondary nutrients (2% sulfur, 7% calcium, 1% magnesium). The polymer-coated urea provides sustained release that plain 10-10-10 blends lack, reducing application frequency. This is the same formulation as Old Cobblers Farm™ 16-10-13 Balanced Nutrition fertilizer.
Answers
Frequently Asked Questions
What is the best fertilizer for asparagus?
The best fertilizer for asparagus is a higher-nitrogen formula with balanced phosphorus and potassium, such as 16-10-13. Asparagus is a perennial crop that depends on strong fern growth after harvest to build carbohydrate reserves in the crown for next spring's spear production. The elevated nitrogen (16%) fuels vigorous fern development, phosphorus (10%) maintains healthy crowns and deep root systems, and potassium (13%) enhances disease resistance and winter hardiness. Added sulfur and magnesium optimize nutrient uptake. Old Cobblers Farm™ Wicked Growth Asparagus Fertilizer 16-10-13 with sulfur and magnesium is purpose-built for asparagus success.
When should I fertilize my asparagus bed?
Fertilize asparagus beds twice per year for best results. Apply the first application in early spring before spears begin emerging, and the second in late summer or early fall after the harvest season ends and ferns are actively growing. The spring application fuels spear production, while the fall application supports fern growth and energy storage in the crown for next year's crop. Avoid fertilizing during the active harvest period, as it can promote thin, spindly spears. Old Cobblers Farm™ Wicked Growth Asparagus Fertilizer 16-10-13 is designed for both spring and fall applications to maximize asparagus productivity year after year.
How much fertilizer does asparagus need?
Apply asparagus fertilizer at a rate of 5–8 pounds per 100 square feet of bed area, or about 1 pound per 2 linear feet of row. Broadcast evenly over the root zone, extending 2–3 feet on both sides of the row to reach the extensive root system. For newly planted crowns, use a lighter rate of 3–5 pounds per 100 square feet. Water thoroughly after application to activate the nutrients. For best results, remove mulch before applying, then replace it afterward. Old Cobblers Farm™ Wicked Growth Asparagus Fertilizer 16-10-13 delivers the right nutrient density for productive asparagus beds.
What NPK ratio is best for asparagus?
Asparagus performs best with a higher-nitrogen fertilizer that also provides strong phosphorus and potassium. A ratio like 16-10-13 is ideal because the elevated nitrogen supports vigorous fern growth, which is how asparagus stores energy for the following spring's spear production. Phosphorus maintains healthy crowns and root systems, while potassium enhances disease resistance and winter hardiness. Added secondary nutrients like sulfur and magnesium further optimize nutrient uptake and promote green, healthy fern development. Old Cobblers Farm™ Wicked Growth Asparagus Fertilizer 16-10-13 provides the optimal NPK ratio for productive asparagus beds.
Is there an organic asparagus fertilizer?
Yes, Old Cobblers Farm offers Wicked Organics 4-6-4 Organic Asparagus Fertilizer, a slow-release blend made from elemental sulfur, animal and vegetable protein meals, natural sulfate of potash, nitrate of soda, and bone char. This organic formula feeds asparagus gradually as soil microbes break down the natural ingredients, providing steady nutrition without the risk of burn or nutrient leaching. It supports both spear production in spring and fern growth in summer while building long-term soil health. Old Cobblers Farm™ offers both conventional (16-10-13) and organic (4-6-4) asparagus fertilizer options to match your growing philosophy.
How do I fertilize a new asparagus bed?
For newly planted asparagus crowns, apply fertilizer at planting time by mixing it into the trench soil where crowns are placed. Use a lighter rate — about 3–5 pounds per 100 square feet — to avoid overwhelming young root systems. After the first year's fern growth dies back in fall, apply a full-rate feeding to build crown energy for the following season. Do not harvest spears in the first two years to allow the crown to fully establish. Old Cobblers Farm™ Wicked Growth Asparagus Fertilizer 16-10-13 is safe for both new plantings and established beds when applied at appropriate rates.
Why does asparagus need so much nitrogen?
Asparagus needs ample nitrogen because its productivity depends entirely on the fern growth that occurs after the spring harvest season. The tall, feathery ferns that grow from summer through fall are the plant's solar panels — they photosynthesize and convert sunlight into carbohydrates that are stored in the underground crown. These stored carbohydrates are what power the following spring's spear production. Without vigorous fern growth fueled by adequate nitrogen, spear production declines dramatically. Old Cobblers Farm™ Wicked Growth Asparagus Fertilizer 16-10-13 provides the elevated nitrogen asparagus crowns need to build energy reserves for abundant annual harvests.
