Fertilizing Kohlrabi: Tips for Bigger, Sweeter Bulbs

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Stephen Albert

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Kohlrabi is a cool-season, heavy-feeding brassica that thrives with proper fertilization. With over 30 years of gardening experience, I’ve learned that feeding your plants correctly—from planting through growth—directly impacts bulb size, flavor, and overall plant health. In this guide, I’ll share step-by-step fertilizing strategies to help you achieve robust, tender, and sweet kohlrabi bulbs.


Step 1: Preparing the Soil​

  • Incorporate compost or aged manure before planting.
  • Work 2–3 inches of organic matter into the top 6–8 inches of soil.
  • Ensure soil is loose and well-draining to allow roots and bulbs to develop.

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Experience Tip: I’ve found that enriching the soil before planting reduces the need for heavy supplemental feeding later.


Step 2: Choosing Fertilizers​

  • Nitrogen-rich fertilizers (like blood meal or fish emulsion) support leafy growth, which feeds the bulb.
  • Balanced fertilizers (N-P-K 10-10-10) can be used for steady growth.
  • Avoid over-fertilizing with nitrogen alone, which can create large leaves but small bulbs.

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Experience Tip: I often use a combination of compost and a light organic fertilizer to encourage both leaf and bulb development.


Step 3: Fertilizing During Growth​

  • Side-dress when bulbs begin to form (about 3–4 weeks after planting).
  • Apply fertilizer evenly around the base, keeping it a few inches away from the crown.
  • Repeat side-dressing every 3–4 weeks for continuous growth.

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Experience Tip: Consistent, moderate feeding yields sweeter, tender bulbs compared to heavy, infrequent fertilization.


Step 4: Micronutrients and Soil Health​

  • Kohlrabi benefits from calcium, magnesium, and boron for strong cell walls and smooth bulbs.
  • Incorporate lime or dolomitic lime if soil is acidic (pH <6.0).
  • Mulching and regular watering help nutrients reach roots efficiently.

Step 5: Fertilization for Container Kohlrabi​

  • Use a high-quality potting mix with compost.
  • Supplement with liquid organic fertilizer every 2–3 weeks since nutrients leach faster in containers.
  • Ensure consistent moisture for optimal nutrient uptake.

My Experience​


Proper fertilization is the key to growing bigger, sweeter kohlrabi bulbs. By preparing the soil, using a balanced feeding schedule, and monitoring micronutrients, gardeners can maximize yield and flavor. Consistent, hands-on care—backed by decades of experience—ensures your kohlrabi thrives from seedling to harvest.

Kohlrabi Fertilization Schedule​

StageFertilizer TypeTiming / FrequencyApplication TipsExperience Tip
Pre-PlantingCompost or aged manureWork into soil 2–3 inches deep before plantingMix into top 6–8 inches of soilPre-enriching soil reduces need for heavy feeding later
Early GrowthNitrogen-rich (blood meal, fish emulsion)2–3 weeks after seedlings emergeApply evenly around base, a few inches from crownSupports leafy growth for bulb development
Bulb FormationBalanced fertilizer (N-P-K 10-10-10)When bulbs begin to form (3–4 weeks after planting)Side-dress around base; water inModerate, consistent feeding yields tender, flavorful bulbs
Ongoing GrowthOrganic liquid fertilizerEvery 3–4 weeks until harvestApply evenly to soil or as foliar feedKeeps nutrients steady for continuous growth
Container PlantsHigh-quality potting mix + liquid fertilizerEvery 2–3 weeksNutrients leach faster in containers; maintain consistent moistureEnsures bulbs develop fully in limited soil volume
MicronutrientsLime, dolomitic lime, or trace mineral mixAs needed based on soil testIncorporate into soil or sprinkle lightly around plantsBoosts calcium, magnesium, and boron for smooth, strong bulbs


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Gardener’s Tip from Experience:
Consistent, moderate feeding and regular monitoring of soil nutrients are key to growing bigger, sweeter kohlrabi bulbs in both gardens and containers.

The post Fertilizing Kohlrabi: Tips for Bigger, Sweeter Bulbs appeared first on Harvest to Table.

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