How to Grow Hydrangea
With their exceptional blooms with a huge diversity of colors, hydrangea makes it irresistible for any homeowner to wish to have it in their garden and hence to know how to plant and grow these rich clusters made of cute, tiny flowers.
What is one of the most amazing qualities of hydrangea is that one can have multicolored flowers sometimes on the same plant. No wonder this plant has an immense power to offer the desired ornamentation to any garden.
Published: October 18, 2022.
Hydrangea plants come in a wide variety, and most of them are suitable for zones 3 to 9.
The size after maturity of a hydrangea plant depends on the variety. While some varieties are as small as only 3-foot tall and wide, some others can grow up to 15-foot tall and 12-foot wide.
Most hydrangea plants bloom best in partial shade. But some will even tolerate full sun or full shade. The level of sunlight hydrangeas can tolerate depends on the location where the grower lives.
Thus in areas towards further north can tolerate more sun, while those further south prefer only a few hours of the morning sun.
Hydrangeas typically bloom in summer. But some bloom earlier in the season and some later (and if the grower is lucky, it keeps blooming even into fall).
Hydrangea comes in a wonderful range of colors, including pink, white, rose, lavender, red and blue. Plus, there is an abundance of varieties, with breeders introducing more options every year.
This amazing shrub heightens gardeners’ expectations of colors and bloom size beyond limits. Several hydrangeas will bloom in one color and then change colors with age.
Plus, certain hydrangea varieties (especially Bigleaf or Mountain varieties) can even be manipulated to become more purple, pink, or blue with soil pH levels and composition.
Hydrangeas also present a wide diversity of characteristics to choose from, e.g., smaller dwarf varieties, standard-sized shrubs, or taller tree-like plants.
The flowers, too, come in four distinct shapes, viz. mophead, panicle, snowball, and lacecap.
They also present the diversity of garden sites where they can be planted, from shrub borders to group plantings to containers.
Even there are various types of blooming patterns, viz. those which bloom on old wood, those which bloom on new wood, and those which bloom on both, often known as “reblooming” or “remontant” hydrangeas.
Basic Requirements of Hydrangea
Most varieties of hydrangea thrive in somewhat moist, porous, rich soils. If the soil is poor, compost should be added to enrich it.
The spot to be chosen for planting should get full sun in the morning and some afternoon shade, though several varieties grow and thrive in partial shade, particularly the Bigleaf hydrangeas.
If the grower lives further north, hydrangeas will bear more sun (probably even full sun across the day).
The size of the plant after full maturity should be taken into account while planting so that the plant can get ample room to grow. Also, the spot should have excellent drainage. And if required, the soil should be amended with compost.
Hydrangeas should not be planted underneath a tree because there would be root competition and lack of sunlight which will prevent it from thriving.
Also, areas that receive gusty winds should be avoided because the winds could snap the plants’ stems.
Planting should be done in spring or fall. It should be made sure there is no threat of frost while planting hydrangeas.
To give the hydrangeas a zesty start, it’s better to amend the soil with up to 15% organic matter and an all-purpose slow-release fertilizer (it’s better to apply half of what is suggested).
Then a hole should be dug as deep as the root ball and twice or thrice as wide. If the roots appear bound, they should be loosened very gently before planting. For this, a few outside roots should be cut, and then the remaining roots should be gently shaken apart. Once they become free, they can spread out into the soil.
Then the plant should be set in the hole, and the hole should be filled half full with soil. Then the plant should be watered. Once the water is drained, the rest of the hole should be filled with soil.
Then again, the plant should be thoroughly watered.
If multiple hydrangeas are to be planted, they should be spaced 3 to 10 feet apart from each other.
Planting Hydrangeas in Pots
While planting hydrangeas in pots, a bagged potting mix should be used instead of garden soil.
This should be mixed with a slow-release fertilizer, and a space of 1-2 inches should be left between the rim of the container and the top of the soil for watering.
The pot should have drainage holes and should be big enough (at least 18 inches in diameter) so that the plant can get ample room to grow. Consider planting dwarf varieties in pots such as Mini Penny, Buttons ‘n Bows, or Little Lime.
Growing Hydrangeas from Cuttings
One of the easiest methods of growing hydrangeas is to grow them from cuttings.
They root easily, and the process is an excellent lesson in propagation. Here’s the method:
On a well-established hydrangea plant, a branch should be found that’s new growth and has not yet flowered. New growth has a lighter color than old growth, and its stem won’t be very rigid.
Now from the tip of such a branch, go 4-5 inches down and give a horizontal cut. It should be remembered that the cutting should have at least 2-4 pairs of leaves or leaf buds.
Now remove the lowest pair of leaves from the cutting, leveling them to the stem. These leaf nodes are the potential spots from where roots will grow.
Hence if it’s possible to remove more than one pair of leaves, it should be done. However, at least two pairs of leaves should be left at the tip end.
If the leaves thus left are significantly large, they should be cut in halves, removing their tip-half. This is to be done to prevent the leaves from rubbing against the sides of the plastic bag, which should be placed over the cutting later on (to maintain the humidity).
There is an optional step here. The leafless part of the stem should be dusted with rooting hormone as well as antifungal powder for plants (both can be bought from a local garden or hardware store). This will stimulate rooting and deter rotting.
Now a small pot should be prepared by filling it with moistened potting mix. Then the cutting should be planted in the soil, pressing it down up to the first pair of remaining leaves. The pot should be lightly watered to remove any air gaps around the stem.
Now the entire pot should be loosely covered with a plastic bag. The bag shouldn’t touch the leaves of the cutting, or else the leaves may rot. (The bag can be kept off the leaves by using chopsticks or something similar to prop it up).
The pot should be placed in a warm spot that won’t receive direct sun or wind.
The cutting should be checked every few days to ensure it’s not rotting, and it should be watered again only once the uppermost layer of soil is dry.
If the grower is lucky enough, the cutting should root in a few weeks (this can be checked by pulling on the cutting. If resistance is felt, it means that roots have formed).
Or simply let the plant grow first leaves and create a root ball - after that, small hydrangeas are ready for replanting.
Through simple propagation methods, one hydrangea can become many. Panicle and Bigleaf hydrangeas can be best propagated through layering in early to mid-summer. Here are steps to do this:
- A small trench should be dug near the hydrangea plant
- Bend a branch down towards the trench to make it touch the soil in the center of the trench (6 to 12 inches of the branch should extend past the trench)
- Scratches in the bark should be made where the branch touches the trench soil
- Now the trench should be filled in, and a brick, stone, or paver should be placed on top
- Over time, the branch will produce its own root system and can be transplanted to a new location
- Oakleaf and Smooth hydrangeas produce new shoots through underground stems. The young plant should be just dug out and separated away from the main plant. Then it can be transplanted to a new spot.
- Transplantation should preferably be done during dormancy, i.e., in fall or winter. The entire root ball should be dug out and replanted immediately.
Growing Hydrangea Trees
By going vertical with hydrangeas, valuable garden space can be saved. Panicle hydrangea trees can be bought from one’s local garden store, or trees can be made on one’s own.
Only a couple of square feet of garden space or a large container will be needed. While using a container, it should be made sure that it won’t be damaged outdoors in the winter.
Because they grow on their own roots, panicle hydrangea trees are as robust as panicle hydrangea shrubs. It’s the same plant pruned into a different shape.
Panicle hydrangeas are strong for Zone 3, so they can be safely overwintered in containers in Zones 4 and warmer. A spot should be found to overwinter the plants in a shed, or the container should be buried in a pile of mulch in a secure spot in the garden, such as against a fence line. Then in early spring, it should be brought out.
Hydrangea trees should be pruned only in early spring before new growth appears.
Whether it’s a ready-made hydrangea tree or the grower has made their own, it will need annual pruning to keep its shape. If pruning is not done each year, all of the grower’s hard work will be wasted, and the desired look will be lost.
Panicle hydrangeas are one of the easiest to grow and hardest. Even in case of wrong pruning, it will most probably recover soon. So, the grower can just enjoy having it without worrying.
Taking Care of Hydrangea
For the first couple of years after planting and during any drought, hydrangeas should be profusely watered. If the soil is too dry, leaves will wilt.
In the case of rich soil, hydrangeas don’t need to be fertilized. In case of light or sandy soil, it’s advisable to feed the plants once a year in late winter or spring.
Excessive fertilizer encourages foliage growth instead of blooms.
During the fall, the plants should be covered to a depth of a minimum of 18 inches with bark mulch, pine needles, straw, or leaves.
If at all possible, the entire plant should be covered, including the tip, with cages made out of chicken wire or snow fencing and loosely filling them with leaves. (However, do not use maple leaves since they usually mat when wet and can choke the plants).
Hydrangeas become happy when kept moist but not when wet. They should never dry out. Hydrangeas planted in containers may need daily watering. Mulch should be added to keep the soil moist.
Immediately after planting, the hydrangeas should be watered frequently for the first few days. Since the roots of the newly transplanted plants may not be functioning with full vigor, the plant should be watered well during the initial days.
Then once the plant is established in the new location, it should be watered whenever the soil seems to dry out. Every time there should be deep watering and not just sprinkling of water.
All through the growing season, hydrangeas should be watered at a rate of 1 inch per week. They should be deeply watered three times a week to promote root growth.
Smooth and Bigleaf hydrangeas need more water, but all varieties are benefited from consistent moisture. A soaker hose can be used to water deeply and keep moisture away from leaves and flowers. Watering in the morning is helpful in preventing hydrangeas from drooping during hot days.
Mulch should be added beneath the plants to keep the soil cool and moist. Organic mulch gets decomposed over time and adds nutrients to the soil improving its texture.
Each hydrangea variety has a different need for fertilizing and benefits from various application timings. The best way to determine the needs is to use a soil test.
- Smooth hydrangeas need fertilization only once, i.e., in late winter.
- Panicle and Oakleaf hydrangeas benefit from two applications in April and June.
- Bigleaf hydrangeas need many light applications of fertilizers in March, May, and June.
Personally, keep the soil moist, well aerated, and rich in organic matter, keep the nitrogen in moderation, with the abundance (but not too much!) of potassium, phosphorus, and microelements, and your hydrangeas will do just fine :)
Pruning of Hydrangea
Pruning of hydrangea is pretty confusing, and it depends on the variety of the plant.
Pruning – Common Hydrangea
The most common shrub of hydrangea planted in gardens is the Bigleaf variety, Hydrangea macrophylla.
Bigleaf (H. macrophylla) and Oakleaf (H. quercifolia) bloom on the stems of the previous season (“old wood”). They are pruned AFTER the flowers fade in the summer.
Buds form in the late summer and flower later the following season, so pruning should be avoided after August 1.
Only dead wood should be cut away in the fall or very early spring.
For pruning, one or two of the oldest stems should be cut down to the base to stimulate branching and fullness.
If the plant is old, damaged, or neglected, all the stems should be pruned down to the base. This will lose flowers for the upcoming season but will also rejuvenate the plant for many years after that.
It’s best to avoid deadheading (removing faded blooms) on the big Mopheads. They should be left as they are over the winter and then should be cut back in early spring (to the first healthy pair of buds). However, deadheading the Lacecaps is fine; they should be cut down up to the second pair of leaves below the flower head.
While growing H. macrophylla and H. serrata varieties in Zones 4 and 5, one should not prune unless absolutely necessary and then do so right after blooming. Or else only the dead stems should be removed in the spring.
Pruning Other Hydrangeas
Smooth (H. arborescens) and Panicle (H. paniculata) are pruned BEFORE the formation of flower buds. These varieties blossom on the stems of the present season (“new wood”).
Pruning should be done in the late winter when the plants are dormant. This is because if the buds are killed during the winter, new buds will be produced by the plant in the spring, which will produce blooms.
Generally, only dead branches should be pruned, and pruning should not be done to “shape” the bush.
Hydrangea - Harvesting
Cutting and Storing Dried Flowers
- If dried hydrangea flowers are to be used to create wreaths or other decorations:
- The flower heads should be cut when the flowers have matured to a papery consistency
- Leaves should be removed from stems and hung upside down in a dry, warm, airy, dark room
- When totally dry (typically a couple of weeks), they should be stored in a dry spot out of direct sunlight
- Flower color can be enhanced by spritzing dry flowers with diluted fabric dye.
Using Hydrangea in a Bouquet
- Freshly cut hydrangea stems should be immediately placed into cold water to prevent wilting
- The woody stems should be recut at a slant underwater.
- Lower leaves on the stems should be removed.
- The stems should now be arranged in a vase and placed in a cool spot.
- The water in the vase should be checked every day, and blooms should be misted with water
- Wilting blooms should be soaked in cool water for 10-15 minutes to revive them.
Best Varieties of Hydrangea to Plant
Hydrangeas fall into two main groups:
Group 1: Plants that Bloom on New Growth (Current Year’s Stems)
The following hydrangea varieties, which get their buds in early summer on new growth, will bloom reliably every year, requiring no special care.
Smooth Hydrangeas (Hydrangea arborescens)
Cultivars of H. arborescens ‘Annabelle’ and ‘Grandiflora’ produce several large (up to 14 inches across), dense, symmetrical blooms in late summer.
Panicle Hydrangeas (Hydrangea paniculata)
Varieties that fit small gardens are ‘Grandiflora’, which is a big, floppy, old-fashioned variety, ‘White Moth’, ‘Tardiva’, and ‘Pee Wee’. ‘Limelight’ produces cool green flowers and grows to a height of 6 to 8 feet.
Group 2: Plants that Bloom on Old Growth (Stems of Last Year)
People living in Zone 8 or warmer should choose these plants. People living in cool climate zones will find it challenging to grow many of these varieties because they set flower buds in the fall.
Although robust to Zones 4 and 5, the buds are vulnerable to damage by an early frost in the fall, a late frost in the spring, or too-cold temperatures when dormant in winter. This, together with untimely pruning, can lead to inconsistent blooming or no blooming at all.
Bigleaf Hydrangea (H. macrophylla)
The ‘All Summer Beauty’ (Mophead) has rich, dark blue flowers that turn pink in soils with near-neutral pH. If its buds are killed in winter, the plant will create new ones in spring and keep blooming.
‘Color Fantasy’ (Mophead) produces deep purple or reddish flowers and dark, shiny green leaves. Its height is around 3 feet.
‘Blue Wave’ (Lacecap) produces rich blue to lilac-blue or mauve to pink flowers.
‘Nikko Blue’ (Mophead) is vigorous with large, blue, round flowers.
Oakleaf Hydrangea (H. quercifolia)
Exceptional fall colors can be expected from ‘Snow Flake, ‘Alice’ and ‘Snow Queen’.
Mountain Hydrangeas (H. serrata)
Examples are ‘Diadem’ and ‘Bluebird.’ When soil is acidic, ‘Preziosa’ forms blossoms of an exceptional blend of light shades of mauve, blue, green, and violet.
Climbing Hydrangeas (H. anomala ssp. Petiolaris)
‘Firefly’ is a recently-patented variety displaying variegated foliage.
Diseases and Pests that can Affect Hydrangea
A white fungus called powdery mildew affects a wide range of plants, including hydrangea, and consumes plants’ nutrients, due to which the plants bloom less and are weakened.
Powdery mildew occurs in many different species, and unlike many other fungi, it thrives in dry, warm climates, although it needs significantly high relative humidity to spread. It doesn’t spread well in cooler, rainy areas. That said, it’s able to infect plants in a wide range of conditions.
Identifying Powdery Mildew
Plants look as if dusted with flour when they are affected by powdery mildew.
The fungus usually begins as circular powdery white spots, which can be seen on leaves, stems, flowers, and fruits. It usually covers the upper part of leaves but may grow on the underside too.
Leaves then turn yellow and dry out. Sometimes leaves may even break, become distorted or twist. Also, the buds and growing tips will be distorted.
Prevention of Powdery Mildew
- Plants resistant to powdery mildew should be chosen.
- Overhead watering should be avoided to reduce relative humidity.
- Overcrowded areas should be selectively pruned to promote air circulation; this will also reduce humidity around the plants.
Controlling Powdery Mildew
All the infected plants should be removed and destroyed. Any infected plant should never be composted since the disease can persist in the compost or spread by wind.
Fungicides should be sprayed on infected plants. Organic fungicides can be prepared with lime sulfur, sulfur, potassium bicarbonate, and neem oil.
Gray mold or Botrytis cinerea can affect any part of the plant and is one of the most common diseases occurring on bedding plants. It easily affects plants that are already damaged or are about to die. Once it occurs, it spreads quickly and can cause extensive damage to healthy parts of the plants.
One of the main causes of gray mold is moisture. Thus the wetter the plants are, the more vulnerable they are of being infected. Also, there should be an injury to the plant before it’s infected.
Identifying Gray Mold Damage
The symptoms of gray mold depend on the kind of plant and climatic conditions. However, usually, spots that seem water-soaked will be formed on the leaves. They might look white in the beginning.
The color of these spots will then change from gray to brown, in the long run covering most of the leaf and causing it to wilt. Due to the brown coloration, most people are confused about gray mold with brown mold.
Under very moist conditions, leaves will get grayish webbing which contains unclear spores. They become active and are released with any activity.
Eventually, stems, buds, and petals may also be infected.
In the long run, all the infected parts of the plant will be covered by an unclear gray growth, and seemingly gray flowers will be caused.
Prevention of Gray Mold
Plants should be handled carefully while transplanting and pruning. Gray mold typically affects injured plants, so plants should be protected from any wounds.
Plants should be kept dry. Overhead watering and watering late in the day should be avoided. Plants should get time to dry off after watering during the day.
Plants should be spaced properly to promote good air circulation.
Space between the plants should be cleaned regularly so as to remove any debris, dead leaves, and cuttings.
Controlling Gray Mold
The infected plants should be removed and destroyed.
Plants should be cleaned thoroughly so that healthy plants may not get infected
Sprays with cultural controls can be used to prevent further infections
Rust is a fungal disease caused by a fungal parasite that affects a broad range of herbaceous and woody plants. Although it rarely kills plants, it decreases their health and flower production.
Rust often thrives in mild, humid conditions. It’s spread through spores from infected plants to healthy ones either by water or wind. Therefore this disease often spreads after watering.
Rust looks similar to the rust occurring on an old bicycle in the shed in the form of white or yellow spots on the upper leaves or orange or reddish blister-like swellings on the underside of leaves, or yellow or orange streaks or spots on the undersides of leaves. Spores are within these formations.
Prevention of Rust
- Plants should be dusted with sulfur early in the season to prevent infection or stop the spread of mild infections
- Plants should be spaced properly to promote air circulation
- Wetting of leaves should be avoided while watering the plants
- There are many effective rust fungicides that can be tried. One’s local nursery can advise about which product should be used.
Sadly, there is no easy method to treat rust. These tips should be tried:
- All infected plants should be removed and destroyed. Replant the area with resistant varieties.
- Clean the area between plants to prevent the disease from spreading.
- Splashing water on leaves should be avoided since this can spread rust.
Slugs are very harmful garden pests and typically occur in humid and moist climates. Any garden is likely to have more slugs, especially in the rainy season.
Slugs are soft-bodied mollusks and not insects. They lack shells and have both male and female reproductive organs. As anyone can expect, their sex life is complex.
The common gray garden slug performs an elaborate hour-long nuptial dance before mating, whereas other species do acrobatic actions while being suspended from threads of slime.
Most garden slugs are one inch long and gray to dark brown. They usually hide in dark, moist places during the day. They only feed at night and remain hidden in the day. So, slug damage can be seen, but it’s hard to find slugs.
But they secrete a slimy substance which makes it easy to know where they are. By digging holes that are six-inch deep and four-inch wide in the garden soil, one can monitor slug activity in their garden.
These holes should be covered with a board and should be checked for slugs after three days. If any of them are seen, these sneaky pests are eating the plants.
Slugs lay their eggs in damp soil or compost. They thrive rapidly in cool and humid conditions.
It’s a good idea to rake the garden in early spring so as to clean up some of the most debris slugs are fond of and also to rake away slug eggs, if any. Large wood chips form hiding areas for slugs, so they should not be used.
The garden should be watered only when necessary to reduce damp spots where slugs congregate.
It’s also useful to have natural predators like ducks and chickens in the garden who eat slugs and their eggs. Also, the number of frogs, toads, snakes, and ground beetles should be increased in the garden.
Also, it’s good to attract firefly larvae and songbirds to the garden because they feed on slugs.
Slugs get a small shock upon being exposed to copper, and they turn back. So, a perimeter should be made around the plants with copper tape.
Getting Rid of Slugs
- A perfect slug trap is to lay boards or pieces of cardboard on the soil around plantings, and the boards should be turned over, and hiding slugs should be scraped into large plastic containers. The containers should be covered and frozen for three hours. The frozen stiff slugs should then be dumped on a compost pile.
- Shallow dishes of beer should be placed around the garden to lure the slugs to a drunken death. Or water should be mixed with cornmeal, baking yeast, molasses, and flour to replace the beer.
- One can even handpick the nasty creatures. This can be done best in the evening twilight or early dawn before they seek shelter from the daytime heat.
- Slugs can be kept away from tender plants by circling the plants with wood ashes (which also provide potassium to plants), copper sheeting, crushed eggshells, pine needles, coffee grounds, coarse sand or diatomaceous earth. These coarse mulches tear the tender underside of slugs.
- An insecticidal spray can be prepared by mixing equal parts 70% alcohol and water (or 1 part of 95% alcohol and 1 ½ parts water), and slugs can be killed.
- Slug damage can be reduced by planting slug-resistant plants like phlox, mint, or astilbe.
Having No Blooms on Hydrangea
Sometimes hydrangeas may not bloom as expected due to a few reasons. The problem is most common with varieties that bloom on old wood, i.e., last season’s growth. First, they may have been pruned at the wrong time, and by mistake, stems may have been removed that would have produced flowers.
Secondly, the flower buds may have been ruined by a hard frost. Some growers cover their plants during cold snaps if this may be any issue.
Lastly, the lack of blooms could be a result of over-fertilizing or excessive shade.
Changing the Color of Hydrangea Flowers
The colors of hydrangea flowers can be changed, but not instantly. Color change may take weeks or even months. And one should wait till the plant is minimum of 2 years old to give it time to pull through from the trauma of its original planting. Also, it should be remembered that it’s easier to change from blue flowers to pink than from pink to blue.
Also, not every hydrangea changes color. The color of some Bigleaf hydrangea (H. macrophylla), particularly Lacecap and Mophead types and H. serrata cultivars change depending on the soil pH.
Acidic soils having a pH less than 5.5 generate blue flowers, whereas soils having a pH higher than 7 generate pink or red flowers.
There is no effect of pH on white flowers. When the pH is between 5.5 and 7, prediction about color becomes difficult. The flowers may be pink, blue, or purple, or even in a blotched pink and blue pattern.
Having hydrangeas in one’s garden is a matter of pride, beauty, and relaxation.
The process of growing these colorful goodies is equally fun and quite easy, and the experience becomes even more rewarding when a riot of colors starts in the garden thanks to the solid hydrangea clusters.
Hydrangea plants can be very decorative and are commonly found in flower gardens, either planted in a permanent position or they are grown in suitable pots.