If you want your hydrangeas to produce those stunning blooms, knowing when do you fertilize hydrangeas is the key to success. Feeding them at the right time makes all the difference between a good shrub and a spectacular one.
This guide will walk you through the best schedule and methods. We’ll cover the what, when, and how so you can give your plants exactly what they need.
When Do You Fertilize Hydrangeas
Timing your fertilizer application correctly is the most important step. Getting it wrong can actually harm your plants or reduce flowering.
The best time to fertilize hydrangeas is in early spring, just as the new growth begins to emerge. A second, lighter application can be made in early summer, but you should stop feeding by late July or early August.
This schedule supports strong growth and bud formation without encouraging tender new growth that could be damaged by winter frosts.
Why Spring Feeding is Crucial
As your hydrangea wakes up from dormancy, it uses stored energy to push out new leaves and stems. A spring feeding provides the essential nutrients to support this burst of growth.
It also helps the plant develop the strong foundation it needs for the upcoming blooming season. Think of it as a balanced breakfast for your shrub.
The Risk of Late-Season Fertilizing
Fertilizing too late in the season is a common mistake. When you apply fertilizer in late summer or fall, you stimulate new growth.
This new growth often doesn’t have enough time to “harden off” before the first freeze. It becomes susceptible to cold damage, which can weaken the entire plant.
Exceptions to the Rule: Potted and Reblooming Types
Hydrangeas growing in containers are an exception. Because nutrients leach out faster with frequent watering, they may benefit from light feeding every two weeks during the peak growing season with a liquid fertilizer.
Also, modern reblooming varieties, like those in the Endless Summer series, can handle a bit more frequent feeding to support their repeated flowering cycles. Always follow the specific product instructions though.
Choosing the Right Fertilizer for Your Hydrangeas
Not all fertilizers are created equal. The type you choose depends on your goals for the plant, particularly its color.
Understanding the N-P-K Ratio
Fertilizer labels show three numbers, like 10-10-10 or 12-4-8. These represent the percentage of Nitrogen (N), Phosphorus (P), and Potassium (K).
- Nitrogen (N): Promotes green, leafy growth.
- Phosphorus (P): Supports strong root development and, crucially, flower production.
- Potassium (K): Aids in overall plant health and disease resistance.
Best Fertilizer for Blue Hydrangeas
For blue flowers, you need acidic soil. To encourage and maintain this color, use a fertilizer that is low in phosphorus and high in potassium.
Look for products labeled for acid-loving plants, like rhododendron or azalea food. Some gardeners also apply soil sulfur to help lower the pH.
Best Fertilizer for Pink Hydrangeas
Pink flowers require more alkaline soil. To encourage pink blooms, use a fertilizer with a higher phosphorus content.
A balanced, all-purpose fertilizer often works well. You can also add garden lime to the soil to gently raise the pH over time.
Organic Options
Many gardeners prefer organic fertilizers. They release nutrients slowly and improve soil structure.
- Compost or well-rotted manure: Apply a layer around the base in spring.
- Bone meal: A great source of phosphorus for flowering.
- Cottonseed meal: Good for acid-loving, blue hydrangeas.
Step-by-Step Guide to Fertilizing Hydrangeas
Follow these simple steps to ensure you feed your hydrangeas correctly and safely.
Step 1: Test Your Soil
Before adding anything, its a good idea to test your soil pH. This tells you if you need to adjust for color and reveals what nutrients might be lacking. You can buy a simple test kit from any garden center.
Step 2: Water Thoroughly First
Always water your hydrangea deeply a day or two before applying fertilizer. This prevents root burn and helps the plant uptake nutrients.
Step 3: Measure and Apply
Read the fertilizer label carefully to determine the correct amount for your shrub’s size. Less is often more—over-fertilizing can damage roots.
Sprinkle granular fertilizer evenly on the soil around the drip line (the area under the outer branches), not right against the main stem.
Step 4: Water Again and Mulch
After applying, water the area again to help move the nutrients into the soil. Then, add a fresh 2-3 inch layer of mulch, like shredded bark, to conserve moisture and suppress weeds.
Common Fertilizing Mistakes to Avoid
Even with good intentions, its easy to make errors. Here’s what to watch out for.
Over-Fertilizing (The Biggest Problem)
More fertilizer does not mean more flowers. Excess fertilizer, especially nitrogen, leads to lots of lush leaves at the expense of blooms. It can also salt the soil and damage roots.
Fertilizing at Planting Time
Do not add fertilizer to the hole when planting a new hydrangea. You can burn the tender roots. Wait until the plant is established and showing its first new growth.
Ignoring Soil Health
Fertilizer is not a substitute for good soil. Amending your soil with compost regularly improves its texture and nutrient-holding capacity, making any fertilizer you do use more effective.
Forgetting to Adjust for Weather
If you’ve had an exceptionally rainy spring, nutrients may have leached away. A light supplemental feeding in early summer might be needed. Conversely, in a drought, its best to hold off on fertilizing until the plant is less stressed.
FAQ: Feeding Your Hydrangeas
Can I use rose fertilizer on hydrangeas?
Yes, rose fertilizer is often a good choice. It’s typically formulated to encourage beautiful blooms, which is exactly what we want for hydrangeas. Just check that the N-P-K ratio is appropriate for your desired flower color.
Should I fertilize hydrangeas in the fall?
No, you should not fertilize in the fall. This can promote new growth that will be killed by frost. Instead, focus on mulching to protect the roots over winter.
What if my hydrangea isn’t blooming?
Lack of blooms is rarely due to fertilizer alone. More common causes are improper pruning (cutting off flower buds), too much shade, or winter bud damage. Assess these factors before increasing feed.
How often should I feed my hydrangeas?
For most in-ground hydrangeas, once or twice a year is plenty. A main feeding in spring and a possible light follow-up in early summer. Potted plants need more frequent, diluted feeding.
Is Epsom salt good for hydrangeas?
Epsom salt provides magnesium. Only use it if a soil test shows a deficiency. Unnecessary use won’t benefit the plant and can disrupt soil balance.
By following this simple timing guide—feeding in early spring and stopping by midsummer—you set your hydrangeas up for a healthy, vibrant season. Remember, the goal is to support the plant’s natural cycle, not force it. With the right fertilizer applied at the right time, you’ll be well on your way to a garden full of breathtaking hydrangea blooms.