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Old Cobblers Farm™ Wicked Growth Strawberry Fertilizer 10-5-13

Grow sweeter strawberries with our 10-5-13 fertilizer with 13% sulfur and 3% calcium. Application rates & berry growing tips from Old Cobblers Farm.

Old Cobblers Farm™ Wicked Growth Strawberry Fertilizer

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OUR STORY

This 10-5-13 strawberry formula is a custom-blended granular fertilizer produced by Green Mountain Fertilizer. The dual nitrogen sources—ammonium sulfate and Purkote polymer-coated urea—deliver nitrogen in a controlled, sustained manner. This is critical for strawberries because excessive nitrogen causes rank vegetative growth, excessive runners, soft fruit, and increased susceptibility to gray mold (Botrytis). The intentionally low 5% phosphorus provides just enough for root maintenance without toxic buildup.

The high potassium content comes from muriate of potash and potassium magnesium sulfate (langbeinite). The 13% sulfur, 3% calcium, and 3% magnesium are secondary nutrients that directly impact fruit quality—calcium strengthens cell walls to reduce soft fruit, magnesium supports chlorophyll production, and sulfur supports flavor compound development. This is the same formulation as Old Cobblers Farm™ Tomato Fertilizer and 10-5-13 Fertilizer.

NPK

10-5-13

Type

Non-Organic

Derived From

Ammonium Sulfate, Purkote (Polymer Coated Urea), Monoammonium Phosphate, Potassium Chloride (Muriate of Potash), Potassium Magnesium Sulfate, Calcium Sulfate (Gypsum). Also provides 13% Sulfur, 3% Calcium, 3% Magnesium.

Best For

Brand

Wicked Growth

NPK Breakdown

N

Provides 10% nitrogen (from ammonium sulfate and polymer-coated urea) for steady growth without the excessive vegetative push that reduces fruit quality in fruiting crops

P

Delivers 5% phosphorus (from monoammonium phosphate) for root establishment and flower initiation—kept intentionally low to avoid phosphorus buildup in established soils

K

Supplies 13% potassium (from muriate of potash and potassium magnesium sulfate) to improve fruit quality, firmness, flavor, color development, and disease resistance

What Is It ?

Strawberry fertilizer (10-5-13) is a specialty blend designed to maximize berry production, flavor, and plant health in both June-bearing and everbearing strawberry varieties. Strawberries need moderate nitrogen to grow healthy foliage without excessive runner production, low phosphorus because they are sensitive to phosphorus overload, and high potassium for fruit sweetness, firmness, and disease resistance. This 10-5-13 formula addresses all three needs precisely. The nitrogen comes from ammonium sulfate for immediate feeding and polymer-coated urea (Purkote) for sustained release, preventing the nitrogen spike that causes leggy growth at the expense of berries. The high potassium (13%) directly influences sugar transport to developing fruit—more potassium means sweeter, firmer, more deeply colored berries. The formula also provides an exceptional 13% sulfur, 3% calcium, and 3% magnesium. This is the same formulation as Old Cobblers Farm™ Tomato Fertilizer and 10-5-13 general-purpose fertilizer. Manufactured by Green Mountain Fertilizer in Milton, Vermont.

When To Apply ?

For June-bearing varieties, the most important feeding occurs immediately after harvest during renovation. Apply 0.5-1 lb per 100 sq ft after mowing and thinning. A second light application in early September supports fall root growth. Avoid spring fertilization of June-bearers as excess nitrogen before fruiting promotes gray mold.

For everbearing and day-neutral varieties, apply 1-2 teaspoons per plant every 4-6 weeks during fruiting (June-September). For commercial acreage, apply 200-400 lbs per acre split into 2-3 applications. Irrigate within 24 hours to prevent salt damage to shallow roots.

How to Apply ?

1. Soil Test

Test soil before the growing season to determine baseline nutrient levels and pH (strawberries prefer 5.5–6.5).

2. New Planting Rate

For new plantings, mix 0.5 lbs per 100 sq ft into the bed before planting runners or transplants.

3. June-Bearer Timing

For June-bearers: apply after renovation (mowing and thinning) in mid-summer to fuel next year's crop.

4. Everbearing Rate

For everbearing/day-neutral: apply 1–2 teaspoons per plant monthly during fruiting for continuous production.

5. Application Method

Broadcast evenly or apply in a ring 4–6 inches from plant crowns where feeder roots are active.

6. Avoid Foliage

Avoid getting fertilizer on leaves or crowns — this causes burn and can promote disease.

7 June-Bearer Timing

For June-bearers: apply after renovation (mowing and thinning) in mid-summer to fuel next year's crop.

How To Store

Wear protective gloves and eye protection during handling. Avoid breathing dust—use a NIOSH-approved respirator in dusty conditions. Wash hands thoroughly after handling. Store in a cool, dry, well-ventilated area protected from weather and moisture. Slightly reactive with oxidizing agents, metals, alkalis. Prevent entry to sewers and surface waters. Keep out of reach of children and pets.

FAQs

1. What is the best fertilizer for strawberries?

The best strawberry fertilizer provides moderate nitrogen for plant growth, moderate phosphorus for root development and flowering, and elevated potassium for berry quality. A 10-5-13 ratio is ideal because the higher potassium directly improves berry size, sweetness, flavor, firmness, and shelf life. Added micronutrients including boron, iron, manganese, and zinc further enhance fruit quality and plant health. Old Cobblers Farm™ Wicked Growth Strawberry Fertilizer 10-5-13 with micronutrients is specifically formulated to produce sweeter, juicier strawberries from both June-bearing and everbearing varieties.

2. When should I fertilize strawberry plants?

For June-bearing strawberries, fertilize in early spring when new growth begins and again after harvest to support runner production and next year's flower buds. For everbearing and day-neutral varieties, fertilize at the start of the season and reapply every 4–6 weeks through the fruiting period. Avoid heavy fertilization during active fruiting on June-bearers, as excess nitrogen can soften berries. Newly planted strawberries should receive a light application 4–6 weeks after planting. Old Cobblers Farm™ Wicked Growth Strawberry Fertilizer 10-5-13 supports both spring and season-long feeding programs.

3. How much fertilizer do strawberry plants need?

For established strawberry beds, apply 1–2 pounds of 10-5-13 per 100 square feet, broadcasting evenly over the planting area. For individual plants, use 1 tablespoon per plant, applied in a ring 3–4 inches from the crown. For container strawberries, add 1 teaspoon per plant every 4–6 weeks. For raised beds, apply 1–2 pounds per 50 square feet. Always water thoroughly after application to dissolve the fertilizer and carry nutrients to the roots. Old Cobblers Farm™ Wicked Growth Strawberry Fertilizer 10-5-13 is easy to measure for precise, consistent feeding.

4. Why is potassium important for strawberries?

Potassium is the most critical nutrient for strawberry fruit quality. It directly influences berry size, sugar content (sweetness), flavor intensity, firmness, and post-harvest shelf life. Potassium also regulates water movement within the plant, improving drought tolerance during the critical fruiting period. Plants with adequate potassium produce berries that are larger, sweeter, firmer, and more resistant to bruising and rot. Deficiency symptoms include small, flavorless berries with browning leaf margins. Old Cobblers Farm™ Wicked Growth Strawberry Fertilizer 10-5-13 delivers 13% potassium specifically to maximize berry quality.

5. Can I use 10-10-10 on strawberries?

You can use 10-10-10 on strawberries, but a formula like 10-5-13 is better optimized for berry production. 10-10-10 provides more phosphorus and less potassium than strawberries ideally need. Established strawberry beds typically have adequate phosphorus, and the extra potassium in 10-5-13 directly improves berry quality. However, 10-10-10 is acceptable for new strawberry plantings where soils need comprehensive nutrition. Old Cobblers Farm™ Wicked Growth Strawberry Fertilizer 10-5-13 with micronutrients delivers the precise nutrient balance strawberries need for maximum sweetness and yield.

6. What micronutrients do strawberries need?

Strawberries benefit from several key micronutrients. Boron improves pollination, fruit set, and berry firmness. Iron prevents leaf yellowing (chlorosis) and supports photosynthesis. Manganese aids in disease resistance and enzyme function. Zinc supports growth hormone production and leaf development. These micronutrients work together with the primary NPK nutrients to produce healthier plants and higher-quality fruit. Deficiencies in any of these can reduce yield and berry quality. Old Cobblers Farm™ Wicked Growth Strawberry Fertilizer 10-5-13 includes boron, iron, manganese, and zinc for comprehensive strawberry nutrition.

7 How do I fertilize strawberries in raised beds?

For raised bed strawberries, broadcast 1–2 pounds of 10-5-13 fertilizer per 50 square feet of bed area before planting, mixing into the top 6 inches of soil. For established beds, top-dress with 1 pound per 50 square feet in early spring and again after the first harvest flush. Keep fertilizer away from plant crowns to prevent rot. Water deeply after each application. Raised beds tend to drain faster and leach nutrients more quickly than in-ground plantings, so slightly more frequent feeding may be beneficial. Old Cobblers Farm™ Wicked Growth Strawberry Fertilizer 10-5-13 is ideal for raised bed growing systems.