What to Do for Hydrangeas in May for Big Blooms & Strong Summer Growth – 6 Easy Tasks to Do Now Before Shrubs Start Flowering

May is an exciting time in the garden. Everything is waking up, putting out new foliage, and even blooming – depending on the plants. For your hydrangeas, this is a vital time when active growth begins to accelerate. What you do for them now will affect their blooms later in the summer and their overall health for the rest of the year.

Hydrangea care in May is all about promoting rapid, healthy growth and supporting plants as they enter the new growing season. Keep in mind that different types of hydrangeas have slightly different needs, but all can benefit from these care tips.

Here’s what you need to do this month to set up your hydrangeas for a summer full of stunning blooms.

1. Do a Spring Feeding

Hydrangeas grow best in rich soil, so hopefully you added compost when you planted them. That boost of nutrients won’t last forever, though, and your plants will appreciate a spring top-up. May is a great time to fertilize hydrangeas because your shrubs are about to enter a period of furious growth.

A balanced, slow-release organic fertilizer like this one from Tractor Supply is a fine choice for feeding your hydrangeas in spring. Choose a product formulated for flowering shrubs or use a general 10-10-10 fertilizer.

Apply the product according to its instructions (typically around the drip line, not the base of the plant) and water thoroughly.

2. Prune Out Dead Wood

If you know anything about pruning hydrangeas, you know that there are two categories based on how they flower: those that bloom on old wood and those that bloom on new wood. This means they need to be pruned at different times of the year.

As it turns out, May is not the ideal time of year to heavily prune either type of hydrangea. However, this is a good time to tidy up your plants.

Before new growth totally obscures them, find and trim out bits of dead or damaged wood. Dead wood is brittle, hollow, and lacks any new green growth. Trim these off at the base with sharp, clean shears. These pro-approved pruners from Felco make quick work of this spring task.

3. Start a Watering Routine

As your hydrangea comes out of dormancy and puts out new growth at a rapid pace, it needs more water. Hydrangeas have fairly shallow roots that dry out quickly. Regular, consistent moisture helps avoid dry roots and supports healthy new growth.

Hydrangeas need about an inch (2.5 cm) of water per week, more during hot and dry periods and if you grow hydrangeas in containers. Deep watering is best, so plan to give your bushes a deep soaking once or twice a week if it hasn’t rained. If you’re growing a hydrangea in a container, it may benefit from daily watering.

Watering hydrangeas can be a tricky balance. Signs you’re overwatering include soil that is often soggy and yellowing leaves. You can tell if your plants aren't getting enough water if their leaves start drooping or there is overall wilting of the entire plant.

Water hydrangeas in the morning and at the base of plants to avoid moisture remaining on leaves, which can trigger disease.

4. Adjust Flower Color

This is a May task for your bigleaf hydrangeas (Hydrangea macrophylla). This is the kind of hydrangea that can change color with blooms that turn pink or blue flowers, depending on the pH of the soil. The pH of your soil affects the availability of aluminum, which in turn influences the color of the flowers.

For blue hydrangea flowers, you need more acidic soil. Pink hydrangea flowers develop in alkaline soil. To acidify your soil, you need to add aluminum sulfate or another acidifying product like this organic soil acidifier from Espoma.

For alkaline soil, you can add garden lime. Your local garden center should have the right products or you can get garden lime from Jobe's on Amazon. Follow the instructions on whichever one you choose.

The month of May, just before the flowers bloom, is the right time in most places to make these soil amendments. But keep in mind that it can take a little time for the changes to appear.

5. Refresh Mulch

If you haven’t done so already, this is a good time to assess and refresh mulch around hydrangeas as needed. Hydrangeas are susceptible to drying out quickly and mulch is important for retaining moisture in the soil. Mulch also regulates temperature, keeping the roots cool during the hottest days of summer.

Ideally, your hydrangeas should have 2 to 3 inches (5-8 cm) of mulch around them. Bark, shredded leaves, and pine needles are good options. This organic mulch from Miracle-Gro at Lowe's is a good choice. Check your current mulch levels and remove any material that looks rotten.

Apply new mulch around each shrub, but leave a little space bare right around the stems. Too much mulch this close can promote moisture retention that can lead to rot.

6. Watch for Pests & Diseases

If you don’t notice signs of common hydrangea diseases or pests until midsummer, they can be very difficult to manage. Start inspecting your shrubs regularly in May for signs of issues that you can tackle early and effectively.

Potential pests include aphids, spider mites, Japanese beetles, and four-lined plant bug. Remove these pests mechanically if you can, either by picking them off or using a strong stream of water. Using insecticides during blooming periods is not ideal for hydrangeas. By catching pests now, you can avoid needing to use these harsher products that can damage the flowers.

Many of potential diseases of hydrangeas are fungal infections. Powdery mildew is the most common and looks like a white or light gray powdery substance on the leaves.

If the infection is minimal, you can remove affected leaves and take steps to improve airflow. Remove some stems if the plant is dense and crowded. Avoid overhead watering to prevent this issue. Leaves and stems that get wet are more prone to disease.

Consider May your setup month for hydrangeas. Good care now will lead to healthier plants later and bigger, more abundant blooms in summer. May is the right time for a lot of this care, but if you are on the edges of the hardiness zones for hydrangeas, you might need to adjust the timing earlier or later.

Most importantly, it’s important to put in the effort in spring hydrangea care now to ensure your shrubs are healthy throughout the growing season.