Why Does My Hydrangea Have Small Flowers? [Causes & What to Do]

One of the most attractive things about hydrangeas is that they have big, beautiful flowers that can become as large as 12 to 18 inches (30.48-45.72cm)! The size and beauty motivated me to plant some hydrangeas in my garden.

But disappointingly, I’ve noticed that my hydrangeas produce much smaller blooms instead of enormous flowers.

Hydrangeas can grow small flowers for several reasons related to their care. They require the correct amount of water, sunlight, and nutrients in the soil, or they will fail to produce large flowers.

Hydrangea blooms are a boon to any garden or home—but it takes some care and attention to produce bountiful blossoms. In this article, I’ll explore why hydrangeas might have small flowers and how to encourage them to grow healthier, bigger blooms.

Table of Contents

Causes of Stunted Hydrangea Flowers

Some hydrangea varieties tend to produce smaller flowers than others—which is something to bear in mind before you try to tweak your hydrangea’s care.

If you’re looking to plant hydrangeas in your garden that will produce massive flowers, you should opt for varieties such as bigleaf hydrangeas and smooth hydrangea, the latter of which have flower heads 12 inches (30.48cm) in size.

If you have a hydrangea variety that’s supposed to produce large flowers, but they’re small, some of the most common reasons why this is happening include the following ones I’ve outlined.

Your Hydrangea Isn’t Getting Enough Nitrogen

Nitrogen, a common ingredient in popular types of plant fertilizer, encourages plants to boost their foliage and flower growth. Common signs that your plant isn’t getting enough of this essential nutrient include:

Fewer leaves.
Fewer flowers.
Undersized plant growth.

However, if you’re giving your plants too much of this essential nutrient, it can cause the plants to struggle. While your hydrangea might experience growth, it won’t bloom. The lack of nitrogen can also cause your hydrangea flowers to dry out and turn brown faster.

Give your hydrangeas a 10-10-10 balanced fertilizer, giving your plants all the nutrients they need. Apply the fertilizer during the summer, and not more than once or twice.

However, to increase the size of your hydrangea blooms, you should consider using a fertilizer with more phosphorus, as The Spruce reports. When you purchase your fertilizer, ensure it has a higher phosphorus content or a fertilizer with a “blossom boost” label, which means it contains more phosphorus.

I’d recommend purchasing JR Peters Classic Blossom Booster Fertilizer (available on Amazon.com). It encourages plants to produce more flowers that also display brighter colors. You can use it on indoor and outdoor plants, which makes it versatile.

Your Hydrangea Isn’t Getting Enough Water

Hydrangeas are thirsty plants. They require that you water them thoroughly at least three times per week. Give them one inch (2.54cm) of water each time. To ensure your plant gets enough water, ensure you water it copiously around its soil to encourage more root growth.

If your hydrangea is in a pot, check that water comes out the bottom, indicating it’s received enough water.

Although hydrangeas want moist soil, it needs to be well-draining so that their roots don’t become waterlogged—this can put the hydrangeas at risk of root rot.

If your hydrangea flowers aren’t growing large, check the plant for signs of underwatering, which include:

Wilting, especially during the hottest time of day.
Stunted growth.

An excellent tip to follow when watering your hydrangeas on hot days is to do so during the morning so that the plants will get enough moisture to prevent them from wilting during blazing hot afternoons.

Your Hydrangea Soil Requires Organic Matter

You should add organic matter to your hydrangea’s soil, as this will encourage its healthy growth, as Chicago Botanic Garden reports.

Practical examples of organic matter include compost or well-composted manure. Adding organic matter to your soil encourages better drainage while also boosting the soil’s microorganisms that aerate and enrich the soil, as SFGate reports. When hydrangeas are in soil that drains well, this encourages their roots to grow.

You should add approximately two inches (5.08cm) of organic matter to your soil. Mix it into the soil during the spring. Then, add organic matter to the soil again during the winter. A two-inch (5.08cm) layer is ideal as it will prevent soil compaction and erosion while enhancing the soil’s beneficial microorganisms.

If your soil drains too quickly, however, you can amend it by adding peat moss or garden mulch to it, as Oregon State University reports.

To test how quickly your soil drains the water, do this test:

Dig a hole that’s 12 inches (30.48cm) deep and wide.
Fill the hole with water.

If you see that the water drains too quickly, the soil is fast-draining. By comparison, if the water sits in the hole for a long time, it could do with improved drainage. You want to see the water drains within two or three hours, indicating the soil has good drainage.

Your Hydrangea Isn’t Getting Enough Sun

If you’ve planted your hydrangea in a shaded area of the garden, this can prevent it from flowering. However, before you move it to a sunnier spot, ensure you check what variety you have, as different ones have different light requirements.

Some hydrangeas like some shade while others thrive in direct sun. For example, if you own panicle hydrangea (hydrangea paniculata), it requires full-sun conditions. It’s ideal for growing if you live in a U.S. city with a lot of sunlight, such as Yuma in Arizona, which experiences approximately 320 sunny days per year.

Most hydrangea varieties will perform well in partial shade. Generally, you should provide your hydrangeas with morning sun and some afternoon shade so they don’t get too hot.

When finding partial-shade conditions for your hydrangeas, avoid planting them underneath trees. This position can cause them to compete for nutrients and water, while winds can ruin their flowers.

You Haven’t Deadheaded the Hydrangea Flowers

Deadheading means removing the spent flowers from a plant. It is best to perform this process throughout the plant’s flowering cycle so that it will look good and experience new flower growth. If you don’t, your hydrangea might not produce a lot of flowers, or it might display smaller blooms.

Here’s how to deadhead hydrangea flowers.

Deadhead your plants when you see flowers have started to dry out and become brown.
With pruners, cut the stem below the flower head. Make sure you cut above the first set of leaves. I’d recommend The Gardener’s Friend Pruners, available from Amazon. They’re ideal for making small-sized, quick cuts. They’re easy to open and close;—all you have to do is flip the latch. They also have a good grip that makes them easy to hold.

Note that you shouldn’t deadhead hydrangeas before winter. This timing is essential because buds formed on the plant underneath the spent flowers will grow the following spring. Leaving the buds intact will also protect them against the harsh winter elements.

You’ve Pruned Your Hydrangea Too Much

Although deadheading your hydrangea is suitable for the plant and encourages flower growth, you shouldn’t prune your hydrangea annually. Unlike other flowering plants, you don’t need to prune most hydrangea varieties yearly if their buds grow on old wood instead of new.

If you’re pruning your hydrangea, only remove spent flowers and any dead growth on the plant. Pruning more than this can cause the plant to grow beautiful leaves, but it will reduce its flower growth.

You Didn’t Protect Your Hydrangea During Winter

Exposing your hydrangeas to extreme winter temperatures like in states like Maine can negatively impact their ability to bloom and grow healthy, large flowers.

Frost can also damage your hydrangea flowers because it kills flower buds. To protect them, cover the hydrangea with cloth or burlap, but don’t wrap it in plastic, as this can damage its blooms.

Ensure the cloth is big enough to cover the sides of the plant and leave an extra six to 12 inches (15.24-30.48cm) extending on the ground, as SFGate reports. You can keep the cloth securely in place with rocks.

You should always cover your hydrangeas when there are cold snaps in your region or throughout the winter if you experience icy winters, and remove them until after the last frost has occurred.

If you have a potted hydrangea that you keep outside, your plant will be less hardy and tolerant of cold conditions than in-ground plants, so you need to give it extra care. A good tip is erecting wire screens around the pot and filling the space with shredded leaves to provide insulation during cold nights.

Final Thoughts

If you’re growing hydrangeas, you’ll want to take special care of them so that they grow healthy and produce large, beautiful blooms. You can do this by:

Giving your hydrangeas morning sun and shade in the hot afternoons.
Feeding your hydrangeas enough nitrogen.
Water your hydrangeas with one inch (2.54cm) of water three times per week.
Deadheading spent hydrangea flowers so new ones can grow.