Shrub Fertilizers - Buy from Manufacturer Dünger

Two Types of Ornamental Shrubs - Two Approaches to Feeding

Ornamental garden shrubs fall into two broad groups with different nutritional priorities.

Flowering shrubs (spirea, forsythia, weigela, viburnum, lilac, hydrangea): the primary goal is maximum flowers and extended bloom. They need boron before bloom for flower bud initiation and P+K after bloom for next season's bud formation.

Foliage and evergreen shrubs (privet, boxwood, dogwood, elderberry): the primary goal is uniform growth, dense crown and vivid foliage color. They need balanced NPK in spring and K+P in autumn for frost hardiness.

Both groups need spring SKU 1 and autumn SKU 601. The difference lies in summer feeding and micronutrient focus.

Spring Feeding: Universal for All Shrubs (April)

When buds begin to swell and open on the shrubs - it is time for the first feeding for all ornamental shrubs without exception.

DÜNGER SKU 1 (N12-P15-K15-S15) - 30-40 g per medium shrub (1-1.5 m) or 25 g/m². N12 triggers active growth of new shoots and leaves. P15 stimulates fine root growth after winter. K15 regulates water balance. S15% improves all-element uptake and protects against root pathogens.

Large shrubs (lilac, viburnum, hydrangea): 50-60 g per bush. Small shrubs (spirea, forsythia): 20-30 g. Spread evenly under the crown and lightly work in, or water thoroughly after.

For hydrangea: apply SKU 1 at an elevated dose (60-70 g per large bush) - hydrangea is one of the heaviest nitrogen consumers among ornamental shrubs.

Flowering Shrubs: Feeding Before and After Bloom

For spirea, forsythia, weigela, lilac and viburnum, two additional feedings are critically important:

Before bloom (when buds are visible, May): DÜNGER SKU 18 (N12-P15-K15-S15-B0.35%) - 25-30 g per bush. Boron B0.35% directly stimulates flower bud differentiation: more buds per branch, brighter color, longer bloom duration. Forsythia and weigela respond especially strongly to B feeding: flower count increases by 20-35%.

After bloom (June-July): DÜNGER SKU 19 (P23-K30) - 20-25 g per bush. Zero nitrogen: the plant has finished flowering and begins forming next year's dormant buds. P23 fuels this process. K30 hardens the wood after bloom and improves frost hardiness. Skipping the post-bloom feeding reduces next season's flower count.

Hydrangea: Soil pH Controls Flower Color

Mophead and lacecap hydrangeas are the only common garden plant where flower color can be deliberately controlled through soil pH management.

Blue flowers: pH 5.0-5.5 + presence of aluminum ions (Al3+). In acidic conditions aluminum becomes plant-available and accumulates in petals, shifting their color. To achieve blue: acidify the soil (sulfur, pine-bark substrate, acidifying fertilizers), add aluminum sulfate 15-20 g/m², and never apply lime.

Pink or purple flowers: pH 6.5+. In alkaline conditions aluminum is unavailable and the pigment remains in the pink/purple range. To achieve pink: apply lime (dolomite) or wood ash.

Hydrangea chlorosis: young leaves yellowing between green veins - iron (Fe) deficiency. Occurs even at borderline pH, or when pH rises locally. Treatment: foliar chelated iron (Fe-EDTA or Fe-DTPA, 3-5 g/10 L) twice, 7-10 days apart. S15% in SKU 1 gently acidifies the soil and improves Fe uptake.

Autumn Feeding: Winter Preparation for All Shrubs (September)

September is the final feeding of the season for all ornamental shrubs. The goal: building carbohydrate reserves in wood and roots, improving frost hardiness and forming healthy buds for next year.

DÜNGER SKU 601 (N5-P14-K21-S6-Si0.3%) - 20-25 g per bush or 20 g/m². N5: minimal nitrogen - does not stimulate soft late growth that cannot harden before frost. P14: supports root system development and dormant bud formation. K21: the key frost hardiness element. Potassium raises the concentration of dissolved solutes in cells - cells freeze at lower temperatures. Shrubs with K deficiency suffer winter dieback at -15°C, while well-fed shrubs survive -25°C. Si0.3%: silicon reinforces bark and cell walls, improves resistance to freeze-desiccation and bark diseases.

Nutrient Deficiency Signs in Ornamental Shrubs and How to Fix Them

• Young leaves yellowing between green veins - iron (Fe) deficiency. Most common in hydrangea at pH above 6.0. Foliar chelated iron 3-5 g/10 L.
• Older leaves yellowing between green veins - magnesium (Mg) deficiency. Foliar magnesium sulfate 20 g/10 L twice.
• Few or small flowers - boron (B) deficiency or missed pre-bloom feeding. Apply SKU 18 before buds appear.
• Brown leaf margins - potassium (K) deficiency. Unplanned dose of SKU 19 or SKU 601.
• Weak spring growth, pale leaves - nitrogen (N) or phosphorus (P) deficiency. Check pH: below 6.0, P is poorly absorbed. Apply SKU 1.
• Shrub doesn't bloom, only foliage - excess N or wrong pruning timing (some shrubs bloom on last year's wood - prune immediately after bloom, not in spring).

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