Hydrangeas are a stunning collection of flowering plants that add a splash of colour to your garden from mid-to-late summer. They are a popular choice for garden enthusiasts with their various shades and colours, including pink, purple, blue, green, and white. This guide provides comprehensive information on planting, caring for, and pruning Hydrangeas to help you enjoy their beauty fully.
Hydrangea Care Basics
Hydrangeas belong to the Hydrangea genus, which includes approximately 75 species of plants. While the different species may vary slightly, their care requirements are generally similar. Here are the main categories of Hydrangeas:
- Bigleaf Hydrangeas: These are the most commonly imagined variety of hydrangeas, known for their large and showy blooms.
- Panicle Hydrangeas: These hydrangeas have cone-shaped flowerheads and offer a unique and elegant look.
- Smooth Hydrangeas: Smooth hydrangeas are native to North America and are known for their round flower clusters and hardy nature.
- Oakleaf Hydrangeas: Named after their oak leaf-shaped foliage, these hydrangeas are characterised by large, cone-shaped flowers and attractive fall foliage.
- Climbing Hydrangeas: These hydrangeas are vines that can climb walls, trellises, or fences, providing a beautiful vertical accent to your garden.
Establishing a Hydrangea
Hydrangeas prefer to be grown in light shade, though they will tolerate more sun if the soil is not too dry. They enjoy a combination of morning sun and afternoon shade with moist clay soils. The recommended acidity will depend on the colour of the flowers. Check out our guide to plants for shaded gardens to learn more if you’re unsure how much shade your garden has.
A common mistake is keeping new plants in their nursery pots too long. This results in the plant not having enough room to grow. So, whether grown in a container or on the ground, make sure to transfer the plant from its nursery pot.
When should you be planting them?
Potted Hydrangeas can be planted all year round, but you do have to be careful with the condition of the soil. The soil should not be too wet, dry or frozen – this can cause damage to their roots. The ideal time to plant them is in spring or autumn, as these risk factors are reduced. If you do plant out in the summer, be mindful of keeping the soil moist.
Where should you plant Hydrangeas?
The ideal planting location does depend on factors in your garden, such as the soil type. If the soil in your garden does not match the plant requirements, it may be best to grow it in a container. Or, you can also add to your soil to make it better suited to your Hydrangeas. Hydrangeas do prefer growing in moist, clay soils. Some Hydrangeas will need more acidic or alkaline soil to get the best colour from the flowers, so it is advised to test the pH of the soil before deciding where to plant them.
Your Hydrangea will be happiest growing in a combination of morning sun and afternoon shade. The more sun the plant gets, the more water it will need. Once you have planted your Hydrangea in the right location, provide the plant with enough water to aid its establishment.
Moving established Hydrangeas
One final thing to note about establishing your plant is how to move it once established. If you wish to move your plant to a different location, this can be done, but it needs to be done correctly. It’s always a good idea to dig the hole in the new location before digging up your plant so it can be planted again immediately. It is important to dig up as much of the root system as possible, keeping it nicely intact. Hydrangea root balls can be heavy; if you’re working with a bigger plant, we recommend getting some help to move it. Once you’ve moved your plant to its new home, be sure to fill up all available space around the roots with soil.
After you have planted your Hydrangea, water it well and put down an organic mulch to ensure that the soil stays nice and moist – this will give it the best start.
Hydrangea Colour Management
The colouring of a Hydrangea’s flowers works differently than most flowers. This means that where most flowers depend on pigments in the flower itself, Hydrangeas depend on the chemical activity in the soil for their colouring. Blooms will change colour depending on the pH of the soil the plant is growing in. Sometimes people can buy Hydrangeas expecting one colour, but due to the soil conditions, they will see blooms of a different colour entirely. Alternatively, the blooms may not be as bright as they expected,
There are test kits you can get to determine the pH of your soil to match the preferred levels for the colour of blooms you want. Blue Hydrangeas need to be grown in a more acidic soil (a pH of 5.5 or lower), whereas pink Hydrangeas should be grown in alkaline soils (a pH of 6.5 or higher.) Purple flowers are a mixture of pink and blue chemicals and require a more neutral pH – between 5.5 and 6.5 is ideal. Ensuring that you balance the pH just right is crucial to keeping your blooms the correct colour.
If you have a blue Hydrangea but don’t have acidic soil in your garden, there are ways of adjusting this. Firstly, you could buy acidic compost and grow the plant in a container. Secondly, you could add other elements to your current soil to lower the pH. For example, you can use Hydrangea colourants and additives made for Hydrangeas specifically or organic acidifiers like sulphur and sulphate.
For pink blooms, the opposite is true. If the soil isn’t alkaline enough, you can also opt to grow in a pot in different compost. Alternatively, you can use additives in the existing soil to change the pH. There are Hydrangea colourants that you can use for more alkaline soil, or if you were looking at more organic options, you can use lime and fertilisers with a lot of phosphorus.
The easiest way of getting those vibrant flowers is to work with what you’ve got and choose your flower colour depending on your soil acidity.
You can also use soil acidity to change the colour of your blooms, popularly done with apple cider vinegar.
Hydrangea Winter Care – when to prune Hydrangeas
Hydrangeas go dormant over winter months when the temperatures become too cold. To help your Hydrangea preserve energy, you can cut the plant back completely or remove damaged or dead stems. It is important to do this before the temperatures drop below zero degrees, as the freezing temperatures can cause damage to open wounds where your Hydrangea has been cut. Protect them from harsh frost by covering the remaining stems with mulch or other forms for plant insulation. If you are buying a Hydrangea in autumn or winter, your Hydrangea has likely already been cut back for you.
“To help your Hydrangeas flourish, grow them in light shade and moist soil. Make sure to remove your Hydrangea from the nursery pot that is provided when purchasing the Hydrangea, as this can limit their growth. I recommend planting your Hydrangea in spring or autumn when the soil is moist but not too wet,” says Chris Bonnett, gardening expert for The Express and owner of Gardening Express.
“For blue Hydrangeas, keep the soil more acidic with a pH level of 5.5 or lower. Pink Hydrangeas should be kept in alkaline soils at a pH level of 6.5 or higher. And for purple Hydrangeas, try to reach a pH level between 6.5 and 5.5. You can purchase pH soil test kits in most garden centres, but it is important to check regularly or when you suspect the colouring has started to fade or change,” says Chris Bonnett, gardening expert for The Express and owner of Gardening Express.
The spacing needed between the chosen plants will range from 90 cm to 2.4 meters (3 to 8 feet). Do some research into the Hydrangea you choose and the ultimate height it is due to grow to, then plant accordingly.
If hydrangeas experience frequent wilting in hot weather, they will inevitably brown and wither. To ensure their well-being during the scorching summer days, it is essential to water these shrubs deeply every few days. It’s crucial to note that shallow hand watering won’t suffice. Additionally, applying mulch around the plants will help retain moisture in the soil for a longer duration.