Best Asparagus Fertilizer (16-10-13): High Nitrogen Slow Release with Sulfur & Magnesium for Maximum Spear Production Buy on Old Cobblers Farm
Asparagus is a perennial that produces for 15–20 years — but only if the crowns get recharged every season. After you stop harvesting spears, the ferns that grow up are the battery charger. This 16-10-13 fuels maximum fern growth so crowns store maximum energy for next spring's harvest.
Old Cobblers Farm™ Wicked Growth Asparagus Fertilizer 16-10-13
by Conventional Fertilizer — Littleton, NH
16% Nitrogen for Fern Growth
After harvest ends, asparagus ferns are the energy factory. More nitrogen = taller, denser ferns = more photosynthesis = more energy stored in the crown = more spears next spring.
Polymer-Coated Slow Release
Purkote technology feeds nitrogen gradually over weeks during the critical fern-growth period. No surge-and-crash — steady nutrition through the entire recharge window.
Sulfur & Magnesium from Langbeinite
Potassium magnesium sulphate delivers sulfur for protein synthesis and magnesium for chlorophyll — both critical for maximizing the photosynthetic output of asparagus ferns.
Post-Harvest Timing is Critical
Apply immediately after your last spear harvest when ferns start growing. This is when asparagus has the highest nutrient demand. A second application in late summer extends the recharge window.
250–333 sq ft Per Bag
At 1.5–2 lbs per 100 sq ft, one 5 lb bag covers a full-sized asparagus bed. Most home growers need just one bag per application.
13% Potassium for Crown Energy
Potassium regulates carbohydrate transport from ferns to crowns. Adequate K ensures the energy produced by ferns actually gets stored where it matters — in the root crown.
New & Established Beds
Works for newly planted asparagus crowns building their root system and for established beds maximizing annual spear production. Adjust rate by bed age.
Trusted by 20,000+ Growers
Developed in Littleton, New Hampshire. Sold nationwide on Amazon, Walmart, eBay, and theoldcobblersfarm.com.
| NPK Ratio | 16-10-13 |
| Item Form | Slow-release granular (polymer coated) |
| Coverage | 250–333 sq ft asparagus bed per 5 lb bag |
| Category | Conventional Fertilizer |
| Type | Flower & Garden |
| Sizes | 5 lb | 10 lb | 15 lb | 20 lb |
| NPK | 16-10-13 |
| Nitrogen | 16% (polymer coated) |
| Phosphorus | 10% available phosphate |
| Potassium | 13% soluble potash |
| Secondary | Sulfur, Magnesium |
| Form | Slow-release granular |
| Rate | 1.5–2 lbs / 100 sq ft |
| Method | Broadcast over bed |
| Frequency | 2x per season (post-harvest + late summer) |
| Sizes | 5, 10, 15, 20 lb bags |
| Best For | All asparagus — Jersey Knight, Jersey Giant, Mary Washington, Purple Passion |
| Feature | Old Cobblers Farm™ Wicked Growth Asparagus Fertilizer 16-10-13 Old Cobblers Farm | Asparagus Alive! Gurney's | Slow-Release Fertilizer Milorganite | Premium Gold All Purpose Dr. Earth | Organics Vegetable Food Expert Gardener | Veg & Tomato Spikes Jobe's Organics | All Purpose Plant Food Vigoro | 13-13-13 All Purpose GroundWork | Performance Organics Miracle-Gro | Garden-Tone Espoma | Happy Frog Tomato & Veg FoxFarm |
|---|---|---|---|---|---|---|---|---|---|---|---|
| NPK | 16-10-13 | Proprietary | 6-4-0 | 4-4-4 | 3-4-4 | 2-7-4 | 10-10-10 | 13-13-13 | 11-3-8 | 3-4-4 | 5-7-3 |
| Form | Slow-release granular (polymer coated) | — | — | — | — | — | — | — | — | — | — |
| Coverage | 250–333 sq ft asparagus bed per 5 lb bag | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed |
| Price / Size | 5 lb | 10 lb | 15 lb | 20 lb | $19.99 | $24.99 | $13.99 | $5.97 | $14.99 | $22.97 | $27.99 | $14.47 | $15.51 | $18.99 |
| Our Take | The asparagus specialist with the highest slow-release nitrogen in ... | — | — | — | — | — | — | — | — | — | — |
Asparagus Alive!
Slow-Release Fertilizer
Premium Gold All Purpose
Organics Vegetable Food
Veg & Tomato Spikes
All Purpose Plant Food
13-13-13 All Purpose
Performance Organics
Garden-Tone
Happy Frog Tomato & Veg
16% Nitrogen for Fern Growth
After harvest ends, asparagus ferns are the energy factory. More nitrogen = taller, denser ferns = more photosynthesis = more energy stored in the crown = more spears next spring.
Polymer-Coated Slow Release
Purkote technology feeds nitrogen gradually over weeks during the critical fern-growth period. No surge-and-crash — steady nutrition through the entire recharge window.
Sulfur & Magnesium from Langbeinite
Potassium magnesium sulphate delivers sulfur for protein synthesis and magnesium for chlorophyll — both critical for maximizing the photosynthetic output of asparagus ferns.
Post-Harvest Timing is Critical
Apply immediately after your last spear harvest when ferns start growing. This is when asparagus has the highest nutrient demand. A second application in late summer extends the recharge window.
