How to winterize hydrangeas

Once you know how to winterize hydrangeas, you can protect your prized shrubs from the elements and enjoy their glorious blooms returning year after year.

With their colorful and showy flowers, hydrangeas make striking garden ideas for beds and borders, and wonderful container displays, so you wouldn't want to lose these floral stars during a cold snap through being unprepared.

Include winterizing hydrangeas in your list of winter garden ideas to ensure that, come the arrival of spring, your treasured plants spring back into life.

'Hydrangeas can usually withstand the winter temperatures but only if cared for properly. Ideally, you want to start caring for your hydrangeas in fall,' explains Chris Bonnett, founder of Gardening Express.

How to winterize hydrangeas – do they all need protection?

Whether you need to winterize your hydrangeas depends on how cold the weather can get where you live.

'Hydrangeas that are exposed to winter temperatures of no less than 5-10ºF (-15 to -12ºC) do not need winter protection,' explains Chris Link, co-owner of Plant Addicts.

If, however, you live in a zone where winter temperatures typically dip below this level for prolonged periods, and you are growing hydrangeas, then an element of protection may be required.

'Hydrangeas that bloom on old wood should be protected in colder climates – zone 6 and below, ' Chris adds. This includes Hydrangea Macophylla – mopheads and lacecaps.

'Hydrangeas that bloom on new wood, however – which includes Hydrangea paniculata and smooth hydrangeas – generally don't need any additional protection,' Chris advises.

Should hydrangeas be cut back for winter?

You can, winterize hydrangeas by cutting them back to try to get rid of any dead branches – this is something that can be added to your list when planning a winter garden.

There are various methods for pruning hydrangeas, and whether you should cut back hydrangeas in the fall or leave them untouched until the following spring really depends on the type of hydrangeas you have and where you live. 

'In zone 7, I keep hydrangeas untouched through the winter and cut them back to the second or third bud from the end of each stem,' says David Angelov, founder of Plant Parenthood garden design and education in Massachusetts.

'Take out all of the previous year's dead stems, up to 3-4 inches from the base. This ensures you're not cutting live wood in the fall. 

'You should not cut hydrangeas back all the way every year, arbitrarily, or you won't have flowers on those hydrangeas that flower on old wood – the stems that came up the previous year,' he adds.

If you do choose to cut back hydrangeas before the winter, then 'aim to do this before the first frosts. If you wait too long, the open cuttings from the dead branches could freeze and ruin your whole plant,' explains Chris Bonnett.

Do so at the same time as you are cutting back other plants, such as the method you would adopt for overwintering geraniums.

How do you prepare hydrangeas for winter?

To prepare hydrangeas for winter in colder areas, add a thick layer of mulch around the base of the plants to protect the crown and roots from freezing temperatures.

'It is also important to properly insulate the hydrangea – you can use a fleece for this or create a frame around the plant and fill this with things like pine cones and leaves,' explains Chris Bonnett. 

To do this:

• Create a frame around the hydrangea plant using branches, 'or if you want something more sturdy that can withstand snowfall, then use chicken wire instead,' says Chris.
• Next add in some insulating materials into the enclosure, such as oak leaves, pine cones, straw or similar.
• 'Be careful not to break the tips off any of the branches as this is where the flower buds have already formed,' says Chris Link.
• 'This frame or cover must be left on the hydrangea all winter and into the spring until the threat of the last frost has passed.'

How to winterize hydrangeas in pots

Hydrangeas can make one of the best winter plants for pots and borders because, if you leave the flower heads in place, they look ethereally beautiful right through to pruning in spring.  

'Any types of hydrangeas growing in pots typically need a little extra protection in colder climates,' says Chris Link.

Try to move the pots into an area where they will be less exposed to freezing temperatures, such as a greenhouse or summerhouse, if possible.

Where the pots can not be moved under cover, one method is to 'place the pot in a bag and fill around the pot with leaves and other garden material, then gently tie the bag together at the top of the pot,' advises Jenny Rydebrink CEO of Gardenize.

'I place the pot in a sheltered part of the garden and then in spring, when the sun and warmth return, I unpack the pot and start to give the plant water and fertilizer again,' she adds.