When To Fertilize Hydrangeas

Knowing when to fertilize hydrangeas is the key to getting those stunning, vibrant blooms everyone admires. If you get the timing wrong, you might end up with lots of leaves and few flowers, or even harm your plant. This guide will walk you through the simple schedule and methods to feed your hydrangeas for their best performance.

Let’s start with the basics. Hydrangeas need nutrients to support their large leaves and bountiful flower clusters. But they aren’t heavy feeders like some other garden plants. Over-fertilizing, especially with the wrong type of fertilizer, is a common mistake. It can lead to weak growth that flops over or increased suceptibility to pests.

Timing is everything. The goal is to support the growth cycle without encouraging new, tender growth at the wrong time of year.

The Best Times of Year to Feed

The main feeding window is in early spring. Apply fertilizer just as the first new growth begins to emerge from the stems. This gives the plant a boost for the coming season’s leaf and flower development.

A second, optional feeding can be done in early summer, around June. This is only for certain types and situations, which we’ll cover below. You should generally stop fertilizing by late July or early August. Fertilizing too late in the season pushes new growth that won’t harden off before frost, risking winter damage.

A Seasonal Fertilization Schedule

Late Winter/Early Spring: This is your primary fertilization. Do it once you see the first green leaf buds swelling.
Early Summer (Optional): A light second feeding for reblooming varieties or plants in poor soil.
Late Summer through Fall: Do not fertilize. Allow the plant to naturally slow down and prepare for dormancy.

Special Timing for Potted Hydrangeas

Hydrangeas in containers need a slightly different approach. Nutrients wash out of pots more quickly with frequent watering. Fertilize potted hydrangeas every two weeks from early spring until late summer with a diluted, balanced liquid fertilizer. This consistent feeding supports their more constrained root system.

What Type of Fertilizer is Best?

Choosing the right food is as important as the timing. A balanced, slow-release fertilizer is often the best choice for most gardeners.

Slow-Release Granular Fertilizer: This is highly recommended. It feeds the plant gradually over several months, providing steady nutrients and reducing the risk of burn. Look for a balanced formula like 10-10-10 or one close to it.
Organic Options: Compost, well-rotted manure, or commercial organic blends are excellent. They improve soil structure as they feed. Apply a layer of compost around the base of the plant in spring.
Liquid Fertilizer: This gives a quick boost and is useful for potted plants. It requires more frequent application, as its effects don’t last as long.

Fertilizer for Blue or Pink Blooms

For bigleaf and mountain hydrangeas (Hydrangea macrophylla and serrata), color can be influenced by soil pH. This is a special case where your fertilizer choice affects bloom color.

For Blue Blooms: You need acidic soil (lower pH). Use a fertilizer for acid-loving plants and consider adding aluminum sulfate as directed.
For Pink Blooms: You need alkaline soil (higher pH). Use a fertilizer with high phosphorus (the middle number) and add garden lime.
Remember, white-flowered hydrangeas are not affected by soil pH and will stay white.

Step-by-Step: How to Apply Fertilizer

Water First: Always water your hydrangea thoroughly a day before you plan to fertilize. This prevents root shock.
Measure Correctly: Read the fertilizer label carefully. More is not better. Use the recommended amount for your plant’s size, erring on the side of less.
Apply Evenly: For granular fertilizer, sprinkle it evenly on the soil starting a few inches from the main stem and extending out to the drip line (where the branches end). Avoid piling it against the stem.
Water Deeply Again: After applying, water deeply. This helps dissolve the fertilizer and carry it down to the root zone.

Signs You’re Fertilizing Correctly (or Incorrectly)

Your plants will tell you if your feeding schedule is working.

Good Signs: Steady, sturdy growth. Deep green leaves. An abundance of large, long-lasting blooms during the flowering season. The plant looks healthy and vigorous overall.

Bad Signs:

Lush leaves, few flowers: Often caused by too much nitrogen (the first number in the fertilizer ratio).
Brown leaf edges or “burn”: A classic sign of over-fertilization or applying fertilizer to dry soil.
Weak, floppy stems: Excessive growth from too much fertilizer makes stems unable to support the flower heads.
Yellowing leaves (chlorosis): This could be a nutrient deficiency, often iron in alkaline soils, indicating the need for a soil test.

The Importance of Soil Testing

If your hydrangeas consistently struggle, a soil test is your best investment. It removes the guesswork. You can buy a simple kit or send a sample to your local cooperative extension service. The test will tell you your soil’s pH and exact nutrient levels, so you can amend it precisley.

FAQ: Your Fertilizer Questions Answered

Should I fertilize a newly planted hydrangea?
No, not right away. Wait until the plant is established and showing its first new growth, usually in its second season. The original potting soil and planting hole amendments provide enough nutrients initially.

Can I use rose fertilizer on hydrangeas?
Yes, you can. Rose fertilizer is typically a balanced, slow-release formula that works well for hydrangeas too. Just follow the label instructions for application rates.

What is the best natural fertilizer for hydrangeas?
Compost is the top choice. It feeds the plant and improves soil health. Other good options include well-rotted manure, bone meal (for phosphorus), and cottonseed meal (for a slight acidifying effect).

How often should you feed hydrangeas?
For in-ground plants, once a year in spring is often sufficient for healthy soil. A second light feeding in early summer may help reblooming types like Endless Summer. Potted hydrangeas need feeding every two weeks during the growing season.

Why didn’t my hydrangea bloom even though I fertilized it?
Fertilizer is just one factor. Lack of blooms is more commonly caused by improper pruning (cutting off flower buds), late spring frosts that damage buds, or too much shade. Over-fertilizing with nitrogen can also limit flowering.

A Note on Watering and Mulching

Feeding goes hand-in-hand with proper watering and mulching. Hydrangeas need consistent moisture, especially in the heat of summer, to utilize those nutrients effectively. Apply a 2-3 inch layer of organic mulch like shredded bark or leaf mold around the base. This conserves moisture, keeps roots cool, and as it breaks down, it adds organic matter to the soil, complementing your fertilization efforts.

Getting the schedule right for when to fertilize hydrangeas is simple once you understand their rhythm. Start with a light hand in early spring, choose a balanced or targeted fertilizer based on your bloom goals, and always pair feeding with good watering practices. By paying attention to your plant’s signals and the simple calendar guidelines, you’ll be rewarded with the vibrant, show-stopping blooms that make hydrangeas a garden favorite. Remember, sometimes less is more, and consistency trumps a heavy-handed approach every time.