How to Plant, Grow, and Prune Hydrangeas?

by B L

How to Plant, Grow, and Prune Hydrangeas?

If you’re looking for a garden flower with show appeal, hydrangea flowers are truly stunning. Large globes of flowers cover this shrub in summer and spring. Although their appearance may seem high maintenance, with the right conditions and care, hydrangeas are actually fairly easy to grow. So grab your garden gloves, because our growing hydrangeas guide will have you ready to plant in no time.

Hydrangeas are excellent for a range of garden sites from group plantings to shrub borders to containers. Varieties abound (every year, it seems, breeders present us with more options!), and gardeners’ expectations of bloom size and color are boundless. To know how your hydrangea will grow, pay attention to the types, defined below. When you know what to expect, delights will be magnified.

When to Plant Hydrangeas
Autumn is the best time to plant hydrangeas, followed by spring planting. The idea is to give this shrub plenty of time to establish a healthy root system before flowering. Do not plant in the heat of summer.
Plant the shrubs in early morning or late afternoon when it’s cooler and the plant is less likely to suffer heat stress.

Where to Plant Hydrangeas
Most hydrangeas will thrive in fertile, well-draining soils that receive plenty of moisture. Add compost to enrich poor soil.
Generally, hydrangeas prefer partial sun. Ideally, they will be given full sun in the morning, with some afternoon shade to protect from the hot midday sun. This is especially true for the Bigleaf hydrangea (H. macrophylla), which is prone to wilting. Some varieties are more tolerant of full sun.
Space hydrangeas anywhere from 3 to 10 feet apart, depending on type. 

How to plant hydrangeas
To plant hydrangeas, simply dig the planting holes 2 feet wider than the root ball. Keep the depth of the hole consistent with the size of the root ball so your plant sits level with or just higher than the surrounding soil. By creating a slight mound, you help increase water drainage away from the base of the plant.

Hydrangea Care Tips
Although the hydrangea’s leaves and flowers appear delicate, they actually don’t require a lot of tender care. These tips provide all you need to know about how to care for hydrangeas.

Water at a rate of 1 inch per week throughout the growing season. Deeply water 3 times a week to encourage root growth. Bigleaf and smooth hydrangeas require more water, but all varieties benefit from consistent moisture. Use a soaker hose to water deeply and keep moisture off the flowers and leaves. Watering in the morning will help prevent hydrangeas from wilting during hot days.
Add mulch underneath your hydrangeas to help keep the soil moist and cool. An organic mulch breaks down over time, adding nutrients and improving soil texture.
Apply fertilizer based on your specific hydrangeas. Each variety has different needs and will benefit from different application timing. The best way to determine your fertility needs is by using a soil test.
Bigleaf hydrangeas need several light fertilizer applications in March, May and June.
Oakleaf and panicle hydrangeas do best with two applications in April and June.
Smooth hydrangea plants only need fertilization once, in late winter.
Protect against pests and disease by choosing cultivars with resistant traits. Leaf spots, bight, wilt and powdery mildew can all appear on hydrangeas. Pests are not common on hydrangeas, but can appear when plants become stressed. Possible pests include aphids, leaf tiers and red spider mites. Properly caring for hydrangeas is your best defense.

How to Grow Hydrangeas from Cuttings

Hydrangeas can easily be grown from cuttings. They root readily and the process makes for a great lesson in propagation. Here’s how to do it:

  1. On a well-established hydrangea, find a branch that is new growth and that has not flowered. New growth will appear lighter in color than old growth, and the stem will not be as rigid. 
  2. From the tip of the branch, move 4 to 5 inches down and make a horizontal cut. Make sure that there are at least 3 to 4 pairs of leaves on your cutting.
  3. Remove the lowest pair of leaves from the cutting, trimming them flush to the stem. Roots grow more easily from these leaf nodes, so if you can afford to remove more than one pair of leaves, do so. Be sure to keep at least 2 pairs of leaves at the tip end of the cutting, though. 
  4. If the remaining leaves are quite large, cut them in half, removing the tip-half. This prevents the leaves from hitting the sides of the plastic bag you will place over the cutting later on (to keep the humidity up).
  5. (Optional) Dust the leafless part of the stem with rooting hormone and an anti-fungal powder for plants (both available at a local hardware or garden store). This will encourage rooting and discourage rotting.
  6. Prepare a small pot and fill it with moistened potting mix. Plant the cutting in the soil, sinking it down to the first pair of remaining leaves. Water lightly to get rid of any air gaps around the stem.
  7. Cover the entire pot loosely with a plastic bag. Make sure the bag isn’t touching the leaves of the cutting, otherwise the leaves can rot. (Chopsticks or something similar can be used to prop up the bag and keep it off the leaves.)
  8. Place the pot in a warm area that’s sheltered from direct sunlight and wind.
  9. Check on your cutting every few days to make sure that it isn’t rotting and only water again once the top layer of soil is dry. With luck, the cutting should root in a few weeks! (Check by gently pulling on the cutting; if you feel resistance, roots have formed.)

How to Change the Color of Hydrangea Flowers
It is possible to change the flowers’ colors, but not instantly. Color correction takes weeks—even months. Wait until the plant is at least 2 years old to give it time to recover from the shock of its original planting. Also note that it’s easier to change blue flowers to pink than pink to blue.

It’s not every hydrangea that changes color. The color of some Bigleaf hydrangeas (H. macrophylla)—especially Mophead and Lacecap types—and H. serrata cultivars change color based on the soil pH.

Acidic soils with a pH of less than 5.5 produce blue flowers; soils with a pH greater than 6.0 produce pink flowers. White flowers are not affected by pH.