Growing Hydrangeas

Planting

• Most hydrangeas thrive in rich, porous, somewhat moist soils. Add compost to enrich poor soil.
• They prefer full sun in the morning, with some afternoon shade; however, many will grow and bloom in partial shade. This is especially true for the Bigleaf hydrangeas.
• Plant in spring or fall.
• Dig a hole as deep as the root ball and 2 to 3 times as wide.
• Set the plant in the hole and fill it half full with soil. Water. After water is drained, fill the rest of the hole with soil.
• Water thoroughly.
• Space multiple hydrangeas about 3 to 10 feet apart.

How to grow hydrangeas from cutting

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:

• 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. 
• 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.
• 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. 
• 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).
• (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.
• 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.
• 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.)
• Place the pot in a warm area that’s sheltered from direct sunlight and wind.
• 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.)

Care

• For the first year or two after planting and during any drought, be sure hydrangeas get plenty of water. Leaves will wilt if the soil is too dry.
• If your soil is rich, you may not need to fertilize hydrangeas. If your soil is light or sandy, it’s best to feed the plants once a year in late winter or spring. Too much fertilizer encourages leafy growth at the expense of blooms. Learn more about soil amendments.
• In the fall, cover plants to a depth of at least 18 inches with bark mulch, leaves, pine needles, or straw in the fall. If at all possible, cover the entire plant, tip included, by making cages out of snow fencing or chicken wire, and loosely filling the cages with leaves. (Do not use maple leaves, as they tend to mat when wet and can suffocate the plant.)

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 5.5 produce pink flowers. White flowers are not affected by pH.

How to prune a hydrangea 

Learn the essentials below, then read more about how to prune hydrangea varieties here.

Pruning Common Hydrangeas

The most common garden hydrangea shrub is the Bigleaf variety, Hydrangea macrophylla.

Bigleaf (H. macrophylla), Oakleaf (H. quercifolia), Mountain (H. serrata), and Climbing hydrangeas (H. anomala subsp. petiolaris) are pruned AFTER the flowers fade in the summer. These varieties bloom on the previous season’s stems (“old wood”).

• Flower buds actually form in the late summer and flower afterwards the following season, so avoid pruning after August 1. 
• Only cut away dead wood in the fall or very early spring.
• To prune, cut one or two of the oldest stems down to the base to encourage branching and fullness. 
• If the plant is old, neglected, or damaged, prune all the stems down to the base. You’ll lose the flowers for the upcoming season, but also rejuvenate the plant for future years.
• It’s best not to deadhead (remove faded blooms) on the big Mopheads; leave them over the winter and cut them back in early spring (to the first healthy pair of buds). It’s fine to deadhead the Lacecaps; cut down to the second pair of leaves below the flower head.
• When growing H. macrophylla (and H. serrata) varieties in Zones 4 and 5, do not prune unless absolutely necessary, and then do so immediately after blooming. Otherwise, remove only dead stem in the spring.

Other Hydrangeas

Panicle (H. paniculata) and Smooth (H. arborescens) hydrangeas are pruned BEFORE flower buds are formed. These varieties bloom on the current season’s stems (“new wood”).

• Prune in the late winter when the plant is dormant. This means that if the buds are killed during the winter, the plant will produce new buds in the spring which will produce blooms. 
• In general, prune only dead branches, and do not prune to “shape” the bush. 

Pests/Diseases

• Gray mold
• Slugs
• Powdery mildew
• Rust
• Ringspot virus
• Leaf spots

Recommended Varieties

There are two main groups of hydrangeas:

GROUP 1: PLANTS THAT BLOOM ON NEW GROWTH

The following hydrangeas, which form their buds in early summer on new growth, will flower reliably each year, requiring no special care.

• Panicle hydrangeas (Hydrangea paniculata)
  • ‘Grandiflora’ is a big, old-fashioned, floppy variety, ‘Tardiva’, ‘White Moth’, and ‘Pee Wee’ fit the scale of small gardens. ‘Limelight’ produces cool-green flowers and grows to a height of 6 to 8 feet.
• Smooth hydrangeas (H. arborescens)
  • ​​​​Look for the cultivars H. arborescens ‘Grandiflora’ and ‘Annabelle’, which produce many large (up to 14 inches across), tight, symmetrical blooms in late summer. 

GROUP 2: PLANTS THAT BLOOM ON OLD GROWTH

If you live in Zone 8 or warmer, choose plants from this group. Gardeners in cool climate zones will find many of them a challenge, because they set flower buds in the fall. Although hardy to Zones 4 and 5, the buds are prone to damage by an early frost in fall, a late frost in spring, or excessively cold temperatures when dormant in winter. This, along with untimely pruning, can result in inconsistent flowering or no flowering at all.

• Oakleaf hydrangeas (H. quercifolia) 
  • You can expect exceptional fall color from ‘Snow Queen’, ‘Snow Flake’, and ‘Alice’.
• Bigleaf hydrangeas (H. macrophylla) 
  • We love ‘All Summer Beauty’ (Mophead), which has profuse, dark blue flowers—turning more pink in soils with near neutral pH. If its buds are winter-killed, the plant will form new ones in spring and still bloom.
  • ‘Nikko Blue’ (Mophead) is vigorous, with large, rounded, blue flowers.
  • ‘Blue Wave’ (Lacecap) produces rich blue to mauve or lilac-blue to pink flowers.
  • ‘Color Fantasy’ (Mophead) has reddish or deep purple flowers and shiny, dark green leaves. It grows to about 3 feet tall.
• Mountain hydrangeas (H. serrata)
  • Examples are ‘Bluebird’ and ‘Diadem’. In acidic soil, ‘Preziosa’ produces blossoms of an extraordinary blend of pale shades of blue, mauve, violet, and green.
• Climbing hydrangeas (H. anomala ssp. Petiolaris) 
  • ‘Firefly’ is a newly-patented variety exhibiting variegated foliage.

Website: www.almanac.com