An increasingly popular garden plant, the hydrangea is an attractive addition to any garden. Quick growing, some varieties will happily grow to 15ft. Hydrangea shrubs are a great way to fill space in a garden or add definition to spaces and edging.
Flowering from spring until early fall they can also be a foundation plant in your planting scheme. This guide will take you through the vital steps that you need to know, from choosing the right variety to planting and general care.
How to Choose The Right Hydrangea
Each variety of plant has a different set of requirements. Some may like lots of sunlight while others prefer shade. One variety may be best suited to growing in a container garden while another will be happier in a woodland garden style planting scheme.
These shrubs are a great way to fill space and add structure to a space. Their flowers will add color to your garden from spring until fall.
Before you purchase any plant take the time to do some research and find a variety that is best suited to your growing conditions. This will not only make your life a lot easier but the plant will be more likely to flourish.
Which Varieties are Best Suited to my Area?
Generally all hydrangea varieties do well if they are able to enjoy the morning sun and some afternoon shade.
Recently “everblooming” varieties have been developed. The most well known cultivars include Endless Summer and Blushing Bride. These are suited to growing in the coolest USDA zones. They also repeat flower during the summer.
Hydrangea Macrophylla comes in two varieties, mopheads and lacecaps. Also known as bigheads, this is the most commonly grown variety. It grows in USDA zones 5-8, although gardeners in cooler climates will need to provide some winter protection. If they are exposed to freezing temperatures they may fail to flower.
Hydrangea Quercifolia, also known as Oakleaf, will happily grow in light shade and sunny positions. As the name suggests the leaves of this variety resemble those of an oak tree. Hardy down to USDA zone 4b, this variety requires sunny, warm spells in order to flower profusely. For this reason they are best grown by gardeners who enjoy long, hot summers. Oakleaf struggles in areas that stay consistently moist.
Hydrangea Panicle such as Peegee are cold hardy cultivars. A large variety, reaching up to 15ft, they are hardy to zones 3a. The variety Grandiflora is particularly suited to cold climates.
Hydrangea Arborescens is also known as smooth hydrangea or snowballs. The latter name comes from the plants distinctive large white flower clusters. A popular garden plant, the flowers look similar to mophead varieties. The cultivar Annabelle grows well in warm and cool climates. It is hardy down to zones 3a.
Different varieties have their own attractions. The bold white snowball like flowers can really stand out against the lush green foliage of the plant.
How to Plant Hydrangea Shrubs
Planting correctly helps plants to thrive and stay healthy.
These plants thrive in well draining soil. They also appreciate lots of organic material. Work a good quantity into the soil before planting. If your soil is heavy work in lots of homemade compost before planting. This will improve the quality of the soil and drainage, helping to prevent root rot.
Hydrangeas also dislike being planted too deeply in the ground. Dig a hole roughly 2 foot wider than the root ball. The hole should also be roughly the same depth as the root ball. When in the hole the plant should sit level or slightly above the soil.
Where to Plant
Plant your hydrangea in a sheltered location so that it can enjoy the morning sun but is protected from the heat of the afternoon sun. North and south facing positions are ideal. The plants will also appreciate some protection from wind. Strong winds can damage foliage and flowers.
When to Plant
The best time to plant is in fall or early spring. This gives the plants plenty of time to establish a healthy root system before beginning to flower. Planting during the cooler parts of the day, early morning or late afternoon, will help to protect against heat stress. Keep the plants well watered until they are established.
Transplant only when the plant is dormant and has lost its leaves. This will be during the latter part of fall or winter.
Whichever variety you choose, remember to plant it in a position where it will not overcrowd other plants. Even with regular pruning the plant will quickly regrow. Planting in a place where it wont overcrowd other plants will save you the trouble of regular pruning.
Remember shrubs require lots of space to grow into. Avoid planting other, smaller plants too close because they may become smothered and stunted.
Growing Hydrangeas in Containers
Hydrangeas can form an attractive part of a container garden. Just make sure that your chosen pot is at least 18 inches in diameter. Non-porous containers will retain moisture better, helping your hydrangea to thrive.
Dwarf varieties such as Mini Penny, Buttons ‘n’ Bows or Little Lime are ideal for container growing. Simply plant as you would in the ground.
Watering and Feeding
Hydrangeas like the soil to be constantly moist. How much water the plant requires varies depending on the variety. Macrophylla hydrangeas require more water than other varieties. Foliage beginning to wilt is a sign that your hydrangea requires more water.
If you find your hydrangeas require lots of water, why not try harvesting rainwater? This can then be used to water plants in the garden, saving you from running up an expensive water bill.
When watering try to water only the soil around the plant. Damp leaves, particularly during the cool evening temperatures, can become a breeding ground for diseases such as powdery mildew.
You can purchase hydrangea fertilizer. Alternatively you can apply a general purpose 10-10-10 fertilizer. This will contain a good to high level of phosphorus, which encourages flower production.
Oakleaf hydrangeas will happily thrive with just two applications of fertilizer in April and June. Smooth hydrangeas require just one application in late winter. Other hydrangea varieties will require regular feeding through spring and early summer. Cease feeding in the fall, this will help the plant to enter its dormant period.
Mulching will help to keep the soil cool and moist. Organic mulches, such as homemade compost will also break down over time. As they break down, the mulch adds nutrients to the soil and giving your plants an extra boost.
Different varieties require different levels of attention. Mophead hydrangeas never need to be pruned. You simply remove the dead branches every fall and await new growth to emerge. Dead flowers can also be removed.
Be careful when pruning and removing what looks like old or dead growth. Some varieties set buds on last years new growth. Pruning this away will lead to a lack of flowers on your plant.
Whichever type of hydrangea you have, the plant will benefit from removing dead stems every fall or early spring. When the plants are 5 years old cut back about one third of the living, older stems. Cut these down to the ground. This is best done in spring or summer and will help to revitalise the plant, encouraging fresh growth to emerge. Repeat this process every year.
Pruning Mophead, Lacecap and Oakleaf Hydrangeas
These plants set blooms on old wood, stems that have been present for at least a year. To avoid removing this season’s buds prune before August. These varieties set buds in August, September and October.
If you are worried about accidentally pruning away flower buds consider growing Remontant hydrangeas. Commonly found in North America, will regenerate flower buds that have been killed by frost or cut off. Endless Summer is one hydrangea variety that does this.
Pruning Peegee and Arborescens Hydrangeas
These hydrangea plants bloom on new wood, or fresh stems. Avoid pruning Arborescens in the spring and Peegee in the summer. This is when the plants are preparing to flower.
Spent flowers can be removed as and when you notice them.
Cut flowers can look attractive on their own or as part of a larger display. Whether you are pruning these shrubs for aesthetic reasons or to create a floral display, be careful not to remove flower buds.
If you are cutting blooms for arrangements, in June or July you can cut the flowers with long stems. This is because the flower buds for the following year are yet to set. From August onwards cut the flowers with short stems. This will ensure that you won’t disturb next years developing buds.
Hydrangea shrubs rarely produce seeds. Propagation is usually done from cuttings.
Take cuttings only from established hydrangea shrubs. Your chosen branch should be new growth that has yet to flower. New growth is lighter in color and its stem is softer.
With sharp secateurs or scissors take a cutting roughly 5-6 inches long from the tip of the stem. There should be at least 3 pairs of leaves on your chosen stem.
Remove the lowest pair of leaves down to the stem. Hydrangea roots emerge easily from leaf nodes. If the remaining leaves are large they can be cut in half.
If you wish you can dust the lower part of the cutting with rooting hormone and anti-fungal powder. Both are readily available at garden centers. However their application is not necessary.
Fill a small, clean pot with moist potting mix. Place the cutting in the soil down to the first pair of remaining leaves. Water lightly and place in a plastic bag. The bag shouldn’t touch the leaves of the cutting, this can cause them to rot. Use small sticks, or chopsticks to keep the bag away from the leaves.
Place your cutting in a warm, sheltered position. A windowsill away from direct sunlight and wind is ideal.
Regularly check the cutting to ensure that it isn’t rotting. Water when the top soil appears dry.
Easy to propagate, with a little practice you will be able to fill awkward spaces in your garden with these attractive shrubs. This will help to create definition and provide structure. It will also attract pollinators and butterflies to your space.
If the cutting is successful roots will form in a few weeks. To check this, gently pull the cutting from the soil. If you feel resistance this means roots have formed and the process is a success.
Oakleaf and Smooth hydrangea plants produce new shoots from underground stems. These can be carefully dug up and separated from the main plant. These young plants can then be transplanted and grown on as new plants.
Flowers Changing Colors
This can sometimes be caused by ingredients in fertilizer. Organic or homemade fertilizers will rarely have this effect.
Generally hydrangea flowers change color in accordance with your soils pH level. Soil with a pH lower than 7 can cause hydrangea flowers to turn blue. If the soil is more alkaline in nature, above pH level 7, the flowers will turn pink. Kits such as the Sonkir Soil pH Meter will allow you to not only test the pH level of your soil but also monitor moisture and light levels.
One of the most fascinating aspects of these shrubs is how the flower changes color depending on the condition of the soil. With a little time and effort you can amend the soil around the plants, creating the color scheme you desire.
If you want to change the colors of your flowers from pink to blue you will need to add aluminium to the soil. Sulfur or peat moss can also help to turn the flowers blue. Changing the flowers from blue to pink is more difficult. To do this you will need to increase the soils alkaline levels.
White hydrangeas don’t change color.
Hydrangea Pests and Disease Protection
Leaf spot, powdery mildew and wilt can all appear on hydrangea foliage. Providing the plants with the correct care will help to prevent most of these problems. There are also a number of disease resistant cultivars available.
If cared for correctly pests and disease will rarely trouble hydrangea shrubs. Instead their long lasting blooms, the plants flower from spring to fall, will become a reliable source of nectar for bees and pollinators.
Pests rarely target hydrangea shrubs. However aphids, red spider mites and others pests can appear if the plant is stressed. These can be washed away with an application of soapy water or a blast from a hose pipe. Again providing the proper care and attention to your hydrangea shrubs is the best form of defence.
Overwintering Hydrangea Shrubs
It is always a good idea to protect your plants if you enjoy freezing winters. As some varieties set flowers on old wood, last year’s growth they are not suitable for pruning back. Instead you will need to mulch the base well with straw, wood bark, homemade compost or leaves. This will help to insulate the plants root system. Piling the mulch as high as 12-18 around the plant. This helps to protect lower, early flowering buds.
If you are able to cover the entire plant, holding the mulch in place with a cage made from chicken wire. If you are using leaf mulch, avoid maple leaves. They mat when wet, suffocating plants. Mulching sensitive plants to protect them from winter temperatures should form part of your annual fall transition process.
Wait until well past the last local frost date before removing the protective mulch.
Container plants can either be mulched or moved undercover for the duration of winter. Remember to water containers that are moved undercover.
Gardeners in cool or colder climates will need to protect the plants during the winter months. An application of organic mulch will not only protect the plants but as it breaks down the mulch will return nutrients to the soil. This will further benefit your plants.
Finally hydrangea leaves and flower buds can be toxic to cats and dogs if consumed.
With the right care and attention hydrangea shrubs are a great way to add color and structure to a garden. Equally suited to container gardens and flower beds, these popular plants will provide you with color from spring until fall.