Hydrangeas are admired for their lush, colorful blooms that turn any garden into a visual delight. But achieving those full, show-stopping flowers isn’t just about planting and watering—it’s about giving your plants the right nutrients at the right time. Fertilization plays a central role in supporting strong root development, healthy foliage, and the abundant flowers hydrangeas are known for. Yet, many gardeners unknowingly make simple mistakes that can prevent their plants from reaching their full potential. This guide will walk you through how to fertilize hydrangeas properly, avoid common errors, and give you a simple homemade fertilizer recipe to help your plants thrive all summer long.
Nutritional Needs of Hydrangeas
Hydrangeas require a balance of essential nutrients to grow and bloom properly. The key macronutrients include:
Nitrogen (N)
Promotes strong leafy growth. However, too much nitrogen can result in lots of leaves but very few blooms.
Phosphorus (P)
Supports root development and plays a crucial role in flower formation.
Potassium (K)
Helps the plant resist diseases and supports overall vigor.
In addition to these, hydrangeas benefit from micronutrients such as magnesium, iron, and calcium. Understanding the nutritional demands of your plant is essential before choosing a fertilizer or setting up a feeding schedule.
Most Common Fertilizing Mistakes
Even well-meaning gardeners can negatively impact their hydrangeas by making the following mistakes.
Overusing Nitrogen
One of the biggest errors is applying too much nitrogen. It’s tempting to push for growth, but excess nitrogen leads to leafy plants with few blooms. Always follow the fertilizer label instructions and aim for a balanced N-P-K ratio.
Choosing the Wrong Fertilizer
Generic fertilizers may lack the specific nutrients hydrangeas need, especially micronutrients. Opt for a fertilizer made for flowering shrubs, ideally with a balanced or bloom-boosting ratio like 10-10-10 or 10-20-10.
Fertilizing at the Wrong Time
Timing your applications is just as important as choosing the right product. Fertilize:
- First in early spring when new growth appears.
- Optionally mid-summer if the plant shows signs of deficiency. Avoid fertilizing in late fall, as it can stimulate new growth that won’t survive winter frost.
Ignoring Soil pH
Hydrangeas are unique in that their bloom color is influenced by soil pH:
- Acidic soil (pH < 6): Blue flowers
- Alkaline soil (pH > 7): Pink flowers
Failing to monitor or manage pH can also affect how nutrients are absorbed. Regular soil testing can prevent both nutrient deficiencies and bloom color surprises.
Not Accounting for Hydrangea Variety
Different hydrangeas have different needs. For example:
- Bigleaf Hydrangeas (Hydrangea macrophylla) are highly sensitive to pH.
- Panicle Hydrangeas (Hydrangea paniculata) are more forgiving and bloom reliably without much pH tweaking.
Understanding your hydrangea type helps you fine-tune your fertilization plan.
How to Fertilize Hydrangeas the Right Way
Start with a slow-release granular fertilizer in early spring. Look for one with a balanced or bloom-boosting N-P-K ratio (like 10-10-10 or 10-20-10). Follow label instructions closely for application amounts based on plant size and age. Water it in thoroughly to activate the nutrients.
In mid-summer, if your plant appears to need a boost (yellowing leaves, stunted growth, few blooms), consider applying a liquid fertilizer every 4–6 weeks. A water-soluble bloom formula works well as a supplement.
Create a Seasonal Fertilization Schedule
A well-balanced schedule makes it easier to stay consistent:
- Early spring: Slow-release granular fertilizer
- Mid-summer (optional): Liquid feed if needed
- Late summer: Avoid further feeding to allow plant to harden off before winter
Always water before and after feeding to protect roots from potential burn.
Homemade Liquid Fertilizer Recipe
Want to go the natural route? Try this DIY liquid fertilizer using common household items:
Ingredients:
- 1 tablespoon of Epsom salt (magnesium boost)
- 1 tablespoon of baking soda (mild pH adjuster and fungicide)
- 1 tablespoon of clear ammonia (provides nitrogen)
- 1 gallon of water
How to use:
- Mix ingredients thoroughly in a watering can or jug.
- Apply every 4–6 weeks during the growing season.
- Use as a soil drench or foliar spray—just avoid direct contact with flowers.
Step-by-Step: How to Apply Liquid Fertilizer
- Moisten the soil before feeding.
- Use a watering can or garden sprayer.
- Apply evenly around the base of the plant, avoiding the leaves.
- Fertilize in the early morning or late afternoon to reduce evaporation and avoid leaf burn.
- Water lightly afterward to help nutrients soak in.
Fertilizing for Bloom Color Control
If you want to shift your hydrangea’s flower color:
To get blue flowers:
- Lower soil pH by adding aluminum sulfate or organic matter like pine needles.
To get pink flowers:
- Raise pH by adding garden lime to the soil.
Make changes gradually and always test pH before adjusting. Over-correcting can damage the plant.
Monitor, Observe, and Adjust
Look for these signs of fertilization issues:
- Yellowing leaves: Potential nitrogen deficiency
- Stunted growth: Nutrient imbalance
- Brown edges on leaves: Over-fertilization
Perform a soil test every 2–3 years to ensure your plants are getting what they need. Adjust your fertilization practices based on growth and bloom results.
Tips for Fertilizing Hydrangeas Successfully
- Water thoroughly before and after feeding.
- Avoid fertilizing during extreme heat or drought.
- Use mulch to retain moisture and reduce nutrient runoff.
- Consider using compost to improve soil structure and feed naturally.
- Mark your calendar to stay on schedule with feedings.
FAQs
Can I use tomato feed on hydrangeas?
Yes, tomato feed can work as it’s high in potassium, which encourages flowering. Just ensure nitrogen isn’t too high.
Why are my hydrangea leaves turning yellow?
This could be due to nitrogen deficiency or poor drainage. Check soil pH and fertilization habits.
Can too much fertilizer kill my hydrangeas?
Yes. Over-fertilization can burn roots, cause leaf browning, and reduce blooming. Always follow instructions.
Do all hydrangeas change color with pH?
No. Only Hydrangea macrophylla (bigleaf) and Hydrangea serrata respond to pH changes. Others, like panicle or oakleaf hydrangeas, do not.
What’s the best fertilizer for blue hydrangeas?
A balanced fertilizer with added aluminum sulfate or acidifying agents helps maintain the low pH needed for blue blooms.