The Complete Guide to Fertilizing Different Hydrangea Varieties
Hydrangeas are beloved garden shrubs known for their spectacular blooms and relatively easy care. However, different hydrangea species have distinct nutritional needs, and understanding these differences is crucial for achieving the best performance. This Just Bloom HK guide will help you fertilize your hydrangeas properly based on their specific variety and your desired results.
Understanding Hydrangea Nutrition Basics
Hydrangeas have unique nutritional requirements that differ significantly from other flowering shrubs:
Nitrogen (N): Promotes leafy growth and overall vigor; moderate amounts needed
Phosphorus (P): Essential for flower bud development and bloom production
Potassium (K): Supports overall plant health, disease resistance, and winter hardiness
Aluminum and Iron: Critical for blue flower coloration in certain varieties
Micronutrients: Magnesium, calcium, and sulfur are important for leaf health
The ideal NPK ratio for most hydrangeas is 10-10-10 or 12-4-8, though this varies by species and desired flower color. Unlike roses, hydrangeas are moderate feeders and can suffer from over-fertilization, particularly excessive nitrogen which promotes foliage at the expense of blooms.
Bigleaf Hydrangeas (Hydrangea macrophylla)
Characteristics: Most popular garden hydrangeas; include mophead and lacecap varieties; flowers can be pink, blue, or purple depending on soil pH; bloom on old wood (and new wood in remontant varieties).
Best Fertilizer Approach: Bigleaf hydrangeas are the most pH-sensitive hydrangeas, and their fertilization must be coordinated with your desired flower color. These are moderate feeders that benefit from balanced nutrition applied at specific times.
For Pink Flowers:
Balanced fertilizer (10-10-10) in early spring
Avoid aluminum sulfate
Add garden lime if soil pH is below 6.0 (aim for pH 6.0-6.5)
Bone meal for phosphorus
Avoid high-phosphorus fertilizers which can inhibit aluminum uptake
For Blue Flowers:
Acidic fertilizer formulated for azaleas/rhododendrons (4-8-4 or similar)
Aluminum sulfate applications: 1 tablespoon per gallon of water, applied monthly March-June
Maintain soil pH 5.2-5.5 for best blue color
Avoid lime and wood ash
Sulfur to lower pH if necessary
For Purple Flowers:
Maintain pH around 5.8-6.2
Balanced fertilizer without aluminum amendments
Let natural soil conditions determine the color
General Recommendations:
Apply slow-release granular fertilizer in early spring (March-April)
Optional liquid feeding in May and June
Stop fertilizing by July 1st to allow plants to harden off for winter
Compost mulch for organic matter
Application tip: Feed lightly and frequently rather than heavily at once. Bigleaf hydrangeas bloom on old wood, so over-stimulating late-season growth can reduce next year's blooms if that growth is winter-killed.
Panicle Hydrangeas (Hydrangea paniculata)
Characteristics: Cone-shaped flower clusters; bloom on new wood; extremely cold hardy; includes varieties like 'Limelight', 'Bobo', and 'Quick Fire'; flowers start white/green and age to pink.
Best Fertilizer Approach: Panicle hydrangeas are the heaviest feeders among hydrangeas and can handle more aggressive fertilization. They bloom on new wood, so promoting vigorous spring growth enhances flowering.
Recommendations:
Balanced fertilizer (10-10-10 or 14-14-14) in early spring
Second application in late May/early June
Optional third feeding in early July for fall rebloom varieties
Slow-release granular fertilizer for sustained nutrition
Compost or well-rotted manure in spring
Bone meal for phosphorus boost
Application tip: These vigorous growers can handle more nitrogen than other hydrangeas. Apply 2-4 tablespoons of granular fertilizer per plant in spring, then half that amount for subsequent feedings. Water deeply after fertilizing.
Special considerations: Tree-form (standard) panicle hydrangeas need slightly more fertilizer to support both root system and top growth. Large, established shrubs may need double the standard application rates.
Smooth Hydrangeas (Hydrangea arborescens)
Characteristics: Native to North America; includes 'Annabelle' and 'Incrediball'; large white (or pink) mophead flowers; bloom on new wood; very cold hardy.
Best Fertilizer Approach: Smooth hydrangeas are light to moderate feeders that prefer organic-based fertilization. They're quite adaptable and don't require intensive feeding programs.
Recommendations:
Balanced organic fertilizer (5-10-5) in early spring
Compost top-dressing annually
Well-rotted manure worked into soil
Optional mid-season boost with liquid fertilizer
Avoid high-nitrogen synthetic fertilizers
Application tip: One good spring feeding is usually sufficient. These native plants evolved in less-than-ideal soils and actually prefer modest nutrition. Over-feeding causes weak stems that can't support the massive flower heads, requiring staking.
Special considerations: 'Annabelle' and similar varieties produce enormous flower heads. If stems are weak and floppy, reduce nitrogen and increase potassium, or simply feed less overall.
Oakleaf Hydrangeas (Hydrangea quercifolia)
Characteristics: Distinctive oak-shaped leaves; cone-shaped white flowers; spectacular fall color; exfoliating bark; bloom on old wood; native to southeastern US.
Best Fertilizer Approach: Oakleaf hydrangeas are light feeders that prefer minimal intervention. As native plants, they're adapted to average soils and can decline with over-fertilization.
Recommendations:
Light application of balanced organic fertilizer (5-5-5) in early spring
Compost mulch (2-3 inches) for slow nutrient release
Minimal supplemental feeding once established
Bone meal every 2-3 years
Avoid high-nitrogen fertilizers
Application tip: For established plants in good soil, an annual compost application may be all they need. Young plants benefit from light spring feeding for the first 2-3 years, then minimal fertilization thereafter.
Special considerations: Over-fertilization can reduce the intensity of fall color and make plants susceptible to disease. Less is definitely more with oakleaf hydrangeas.
Mountain Hydrangeas (Hydrangea serrata)
Characteristics: Similar to bigleaf but more compact; extremely cold hardy; delicate lacecap flowers; color changes with pH like macrophylla.
Best Fertilizer Approach: Mountain hydrangeas have similar needs to bigleaf hydrangeas but are generally more modest feeders due to their smaller size and slower growth rate.
Recommendations:
Half-strength applications compared to bigleaf hydrangeas
Balanced fertilizer (10-10-10) or acidic formula depending on desired color
Aluminum sulfate for blue flowers (same pH requirements as macrophylla)
Light feeding in early spring only
Avoid over-fertilization which causes excessive growth
Application tip: Use about half the fertilizer amount you'd apply to a bigleaf hydrangea of similar age. These compact plants don't need heavy feeding.
Climbing Hydrangeas (Hydrangea anomala petiolaris)
Characteristics: Vigorous woody vine; white lacecap flowers; slow to establish but then very vigorous; bloom on old wood; shade tolerant.
Best Fertilizer Approach: Climbing hydrangeas need different fertilization strategies depending on their age. Young plants establishing need regular feeding, while mature plants need minimal intervention.
Young Plants (Years 1-5):
Balanced fertilizer (10-10-10) in spring
Monthly liquid feeding during growing season
Focus on root and vine development
Higher nitrogen acceptable to promote growth
Established Plants (Year 6+):
Minimal feeding required
Light spring application of balanced fertilizer
Compost mulch annually
Avoid over-feeding which causes excessive foliage at expense of flowers
Application tip: The common saying "first year sleep, second year creep, third year leap" applies to feeding—increase fertilization as the plant establishes, then reduce once it's vigorous.
General Fertilizing Guidelines for All Hydrangeas
Critical Timing Rules
Early Spring (March-April): Primary feeding time for all hydrangeas. Apply fertilizer as buds begin to swell but before leaves fully emerge.
Late Spring/Early Summer (May-June): Optional second feeding for vigorous growers (panicle and smooth hydrangeas). Avoid for varieties that bloom on old wood if in cold climates.
Mid-Summer (by July 1): Absolute cutoff for fertilization. All hydrangeas need time to harden off for winter. Late feeding can cause tender growth that's vulnerable to winter damage and reduces flowering.
Fall: NO FERTILIZATION. Apply compost mulch only, no active fertilizers.
Application Methods
Granular Fertilizers:
Broadcast evenly around drip line (outer edge of branches)
Keep fertilizer 6 inches away from main stems
Use 2-4 tablespoons per foot of plant height
Water thoroughly after application
Scratch lightly into top inch of soil
Liquid Fertilizers:
Dilute to half-strength for hydrangeas
Apply to moist soil, never dry
Can be used as foliar feed early morning
Good for quick nutrient boost or correcting deficiencies
Apply every 2-4 weeks during active growth (stop by July 1)
Organic Amendments:
Apply as 2-3 inch mulch layer around base
Keep mulch 3-4 inches from stems
Replenish annually in spring
Work aged manure into top 2-3 inches of soil
Color Manipulation for Bigleaf and Mountain Hydrangeas
Achieving Blue Flowers:
Test soil pH—must be below 5.5 for true blue
Lower pH with sulfur if needed (takes several months)
Apply aluminum sulfate: 1 tablespoon per gallon water, monthly March-June
Use acidic fertilizer formulations
Avoid phosphorus which binds aluminum
Mulch with pine needles or oak leaves
Achieving Pink Flowers:
Test soil pH—must be above 6.0 for true pink
Raise pH with garden lime if needed
Use balanced fertilizer without aluminum
Add dolomitic lime in fall (1-2 cups per plant)
Avoid aluminum sulfate completely
White and Green Varieties:
Cannot change color regardless of soil pH
Use balanced fertilizer (10-10-10)
No need for pH manipulation
Focus on overall plant health
Soil Preparation and pH
Ideal pH Ranges:
Blue flowers: 5.2-5.5
Purple flowers: 5.5-6.0
Pink flowers: 6.0-6.5
White varieties: 6.0-7.0 (adaptable)
Soil Testing:
Test annually for color-changing varieties
Test every 2-3 years for others
Test in fall and adjust over winter
Retest in spring before fertilizing
pH Adjustment Timeline:
Raising pH: 3-6 months with lime
Lowering pH: 3-6 months with sulfur
Plan ahead for next season's desired color
Hydrangea Growth Stages
Year 1 (Establishment):
Minimal fertilization
Focus on watering and root development
Light spring feeding only (half normal rate)
Bone meal at planting
Years 2-3 (Development):
Begin regular fertilization schedule
May not bloom heavily yet (especially old-wood bloomers)
Build plant framework
Standard fertilizer applications
Year 4+ (Maturity):
Full fertilization program
Maximum bloom potential
Adjust based on plant performance
May need more fertilizer as plant size increases
Signs of Proper vs. Improper Fertilization
Properly Fertilized Hydrangeas:
Deep green foliage
Strong, upright stems
Abundant blooms appropriate to variety
Consistent growth year to year
Good disease resistance
Appropriate flower color (if manipulating pH)
Over-Fertilized Hydrangeas:
Excessive dark green foliage
Weak, floppy stems
Reduced flowering ("all leaves, no blooms")
Leggy growth
Increased susceptibility to pests and disease
Leaf burn or browning edges
Poor winter hardiness
Under-Fertilized Hydrangeas:
Pale or yellowing leaves (chlorosis)
Stunted growth
Small, sparse blooms
Thin, weak stems
Poor disease resistance
Slow recovery from winter or pruning
Common Nutrient Deficiency Symptoms
Nitrogen Deficiency:
Overall yellowing, especially older leaves
Stunted growth
Small leaves
Phosphorus Deficiency:
Purple or reddish leaf tints
Poor flowering
Slow growth
Potassium Deficiency:
Brown leaf edges
Weak stems
Poor disease resistance
Iron Deficiency (Chlorosis):
Yellowing between leaf veins (veins stay green)
Common in alkaline soils
Treat with chelated iron or iron sulfate
Often indicates pH too high
Magnesium Deficiency:
Yellowing between veins on older leaves
Treat with Epsom salts (1 tablespoon per gallon water)
Organic vs. Synthetic Fertilizers for Hydrangeas
Organic Options:
Compost: Best all-around amendment, improves soil structure
Well-rotted manure: Balanced nutrients, slow release (must be aged 1+ year)
Bone meal: Excellent phosphorus source for flower production
Blood meal: Nitrogen source (use cautiously)
Alfalfa meal: Balanced nutrients plus growth hormones
Coffee grounds: Acidifying effect, slow nitrogen release (good for blue varieties)
Fish emulsion: Quick-acting liquid nitrogen source
Kelp/seaweed: Micronutrients and growth regulators
Synthetic Options:
Slow-release granular: Convenient, consistent feeding (Osmocote, Miracid)
Water-soluble: Quick results, good for deficiency correction
Specialty hydrangea formulas: Designed for specific needs
Aluminum sulfate: For blue flower color
Iron chelate: For chlorosis correction
Best Approach: Many gardeners combine organic soil building (compost, manure) with targeted synthetic applications for color control or quick corrections. Organic fertilizers are gentler and improve long-term soil health.
Special Circumstances
Hydrangeas in Containers
Container hydrangeas have different needs than in-ground plants:
Fertilize more frequently (every 2-3 weeks during growth)
Use half-strength water-soluble fertilizer
Slow-release granular at 1/3 package rate
Nutrients leach quickly with watering
Monitor more closely for deficiencies
Repot every 2-3 years with fresh potting mix
Newly Planted Hydrangeas
No fertilizer at planting except bone meal mixed into hole
Water only for first 4-6 weeks
Begin light feeding (half-strength) after 6 weeks if planted in spring
Fall plantings: no fertilizer until following spring
Focus on establishment, not growth
Hydrangeas in Shade
Shade reduces photosynthesis and nutrient needs:
Reduce fertilizer by 25-50%
One spring feeding usually sufficient
Avoid late-season feeding
Focus on slow-release organic amendments
Over-feeding causes weak, etiolated growth
Hydrangeas Not Blooming
Before adding more fertilizer, check:
Pruning: Improper pruning removes flower buds (critical for old-wood bloomers)
Age: Young plants may not bloom for 2-4 years
Winter damage: Cold kills flower buds on old-wood varieties
Too much nitrogen: Switch to low-nitrogen formula (5-10-10)
Insufficient sun: Most need at least 4-6 hours
Too much shade: Reduces bloom production
If the above are correct:
Switch to bloom-booster formula (low N, high P)
Add bone meal or superphosphate
Reduce nitrogen significantly
Be patient—sometimes takes a year to see results
Transplanted or Divided Hydrangeas
No fertilizer for first growing season
Water consistently instead
Begin light feeding in second season
Return to normal schedule in year 3
Expect reduced blooming for 1-2 years
Regional Considerations
Cold Climates (Zones 3-5):
Stop fertilizing earlier (mid-June)
Favor hardy varieties (paniculata, arborescens, some serrata)
Avoid stimulating late growth vulnerable to frost
Focus on winter hardiness over bloom size
Moderate Climates (Zones 6-7):
Standard fertilization schedules work well
All hydrangea types thrive
Good balance of growth and hardening off time
Can extend feeding into early July
Warm/Hot Climates (Zones 8-10):
May need more frequent watering which leaches nutrients
Lighter, more frequent feeding
Provide afternoon shade to reduce stress
Some varieties (especially macrophylla) struggle with heat
Focus on oakleaf and panicle varieties
Mulch heavily to conserve moisture
Coastal Areas:
Salt tolerance varies by species (oakleaf and macrophylla are more tolerant)
May need magnesium supplementation
Frequent rain can leach nutrients
Monitor pH more carefully
Month-by-Month Hydrangea Care Calendar
March: Apply main fertilizer as buds swell; test soil pH; adjust pH if needed for color change
April: Monitor new growth; apply aluminum sulfate for blue flowers (first application)
May: Optional second feeding for vigorous varieties; continue aluminum sulfate for blues; deadhead spent blooms
June: Last chance for fertilization (early June only); final aluminum sulfate application; mulch to conserve moisture
July: NO FERTILIZATION; water consistently; deadhead as needed
August: NO FERTILIZATION; water during dry spells; enjoy blooms
September: NO FERTILIZATION; reduce watering as temperatures cool; allow plants to harden off
October: Apply compost mulch for winter; clean up fallen leaves; do NOT fertilize
November-February: Dormancy period; no fertilization; protect tender varieties if needed
Fertilizer Application Rates by Plant Size
Small Shrubs (1-3 feet):
2-3 tablespoons granular fertilizer
1 gallon liquid fertilizer solution
Medium Shrubs (3-5 feet):
4-6 tablespoons granular fertilizer
2 gallons liquid fertilizer solution
Large Shrubs (5+ feet):
8-10 tablespoons granular fertilizer
3-4 gallons liquid fertilizer solution
Tree Forms/Climbers:
1/2 to 1 cup granular fertilizer
4-5 gallons liquid fertilizer solution
Always water thoroughly before and after fertilizing to prevent root burn.
Just Bloom Florist tips
Hydrangeas are relatively forgiving plants that don't require intensive fertilization programs. The key to success is understanding your specific variety's needs, timing fertilization appropriately, and knowing when to stop feeding. Most hydrangea problems stem from over-fertilization (particularly excessive nitrogen), improper pruning, or attempting to grow the wrong variety for your climate rather than nutritional deficiencies. Start with a simple program of one balanced spring feeding, observe your plants' responses, and adjust as needed. Remember that for bigleaf and mountain hydrangeas, color manipulation through pH and aluminum requires planning and patience. With proper fertilization matched to your variety, your hydrangeas will reward you with spectacular blooms and healthy growth for many years to come.
