If you have bigleaf hydrangeas (Hydrangea macrophylla) in your landscape or are thinking about planting some, it's important to know the best practices for hydrangea care. Bigleaf hydrangeas are widely popular low-maintenance perennial shrubs that are hardy in USDA Zones 6-9. As long as you meet their basic needs in the appropriate season and avoid pruning them at the wrong time, these plants will bloom spectacularly for many years to come.
Bigleaf Hydrangea Care Season by Season
Taking care of your bigleaf hydrangeas requires meeting their seasonal maintenance needs. With the exception of the trademarked Endless Summer hydrangeas, bigleaf hydrangeas bloom on old wood (stems from the previous season rather than new growth). This impacts when they need to be pruned and maintained. Follow care instructions for Endless Summer hydrangeas if you have that type. Otherwise, the suggestions listed below will help you take great care of your bigleaf hydrangea plants.
Winter Bigleaf Hydrangea Care
Bigleaf hydrangeas are deciduous (not evergreen) shrubs that go dormant in the winter. Even so, because their blooms start to form at the end of summer, they need to be protected from hard freezes. Check the cold hardiness of your hydrangea variety to find out what temperature requires protection, or simply err on the side of caution. You'll never be sorry that you protected your plants when the temperature dips very low, but you might regret failing to do so.
- Loosley mulch around the base of each hydrangea plant, adding to the previous season's mulch. The mulch layer should be between six and eight inches deep. This will help protect the root ball from freezing.
- During a hard freeze, cover your plants to protect the new buds that began forming at the end of summer. For an easy solution, cover them with a sheet, blanket, or cardboard box.
- It is best to avoid pruning bigleaf hydrangea in the winter to avoid damaging new flower buds that began at the end of summer.
- If the winter is extremely cold, there may be so much related damage to the plant that you really need to remove damaged foliage to protect overall plant health. Do so very carefully, and realize that it will reduce the number of summer blooms.
Spring Bigleaf Hydrangea Care
If you're going to add hydrangeas to your garden, spring is the best time to plant or transplant them. Be sure to mulch and thoroughly water new plantings. Spring is also the right time to start fertilizing your plants in advance of the summer blooming season.
Fertilize in March and May
Fertilize your hydrangeas one time in March and one time in May, being sure to water in the fertilizer thoroughly once you apply it to the ground.
- Use a 10-10-10 or 8-8-8 nitrogen, phosphorous, and potassium (NPK) fertilizer.
- Lightly sprinkle fertilizer granules on the ground directly below the drip line, which is the ground directly under the tips of the tree branches. Think about it like this: If water dripped down the branches, the drip line is where it would fall.
Water Weekly
Water your plants weekly during the spring, unless it is raining a lot. The goal is to keep the roots moist without over-watering them. If they appear wilted, that means they need more water.
Adjust the Soil pH for Bloom Color
If you want to adjust the bloom color of established plants, apply aluminum sulfate (to make them blue) or hydrated lime (to make them pink). You can do this via watering so you don't have to disturb the soil.
- Dissolve one tablespoon of aluminum sulfate or hydrated lime (depending on what color you want) per gallon of water.
- Drench the soil around the plant several times during each month of March, April, and May in order to change the soil's pH level. (This counts as watering the plant, so don't overdo it.)
- Avoid getting the liquid on the plant's leaves, as the hydrated lime or aluminum sulfate could potentially damage the leaves.
Refresh Mulch
If needed, refresh the mulch around your hydrangeas. It doesn't have to be as thick as in the colder months. A few inches will continue to help protect the shallow roots these plants have.
Propagate New Plants
Once hydrangea leaves start filling in, you can take stem cuttings to propagate new plants. Propagating hydrangeas is as simple as snipping a stem and putting it in soil for a few weeks to root.
Note: Do not prune bigleaf hydrangeas in the spring, unless they are the Endless Summer type.
Summer Bigleaf Hydrangea Care
Summer is when bigleaf hydrangeas really shine, as they bloom throughout most of June and July. They may need more water than usual if conditions are hot and dry. They'll need to be pruned in late summer.
- Fertilize your hydrangeas again in July, using the same procedure recommended for spring (see above).
- If needed, add mulch to continue protecting the shallow roots of your plants.
- You can plant or transplant hydrangeas during summer, but don't do so in extreme heat. Expect the plant to experience transplant shock, which will result in the loss of blooms, buds, and/or leaves.
- You can continue taking stem cuttings of hydrangeas to propagate new plants through late summer. As long as the leaves are still lush, you can keep on snipping cuttings to root.
- Prune your bigleaf hydrangeas in late July, as soon as they finish blooming or even as the blooms start to fade.
- Finish your pruning before August 1, because flower buds for the following year will start to form around that time. Pruning after buds begin forming will negatively impact next year's flower production.
- Use pruners to snip off flower heads and snip other shoots just above nodes in order to encourage the stems to branch into the desired shape.
Fall Bigleaf Hydrangea Care
Fall is the time to prepare your hydrangeas for winter. You should have already pruned them, so there's not much to do in the way of hydrangea care during autumn.
- Keep watering your hydrangeas weekly unless they're getting at least an inch of rain every week. You can pause watering them (until spring) once the ground freezes in late fall or winter.
- In mid to late fall, use compost or another type of organic matter to topdress your planting beds or other locations where hydrangeas are planted.
- Put a layer of mulch approximately six inches thick on top of the compost. This is essential in areas with cold winters; it's beneficial everywhere hydrangea can be grown as a perennial.
Note: Do not prune bigleaf hydrangeas in the fall unless you have the Endless Summer type. Fall pruning is done only on hydrangeas that bloom on new wood, which is not what other bigleaf hydrangeas do.
Special Considerations for Hydrangeas in Pots
Bigleaf hydrangeas grow well in containers. The suggestions above work for them, though there are a few special considerations for hydrangea care in pots.
- One problem with growing hydrangeas in pots is that plants in containers dry out faster than those in the ground. You'll need to water them more frequently than in-ground plants.
- Drainage is another common problem with growing these plants in pots. Keep an eye on containers to make sure water is draining properly. If it isn't, you'll need to drill more holes in or unblock ones that are already there.
- One good thing about growing hydrangeas in containers is that it's easy to protect them from hard freezes. Just bring them indoors when the temperatures drop really low.
Make the Most of Your Hydrangeas
Follow these season-by-season bigleaf hydrangea care tips, and you'll be the proud owner of some gorgeous, healthy, and productive shrubs. Your landscape will be beautiful with minimal effort. You won't even have to tell anyone just how easy it is to keep your hydrangeas looking so terrific.
