Looking After Hydrangeas
Hydrangeas are a beautiful seasonal plant. They are generally trouble free, and easy to grow in either pots or the garden.
Hydrangeas grow well in sun - shade. Morning sun is ideal; they can get a bit thirsty & even sun burnt in the hot summer afternoon sun.
Hydrangeas flower from late spring through summer, with a gracious fading charm through autumn into winter.
Heading into winter, their leaves turn yellow and drop, their flowers fade to brown, and they get a bit manky looking. Don't be tempted to prune & deadhead too soon!
To see through this "brown out" period, I swap out pots, with counter seasonal, winter flowering & foliage plants. Likewise in the garden, I combine Hydrangeas with other plants which have some winter interest. Useful companion plants for Hydrangeas include Daphnes, Pieris, green Hellebores, and miniature Rhododendrons.
Best time to prune
It's best to hold off pruning Hydrangeas until mid-late winter. Don't be tempted to dead head and prune too early. Pruning stimulates new growth, which will be burnt by frosts and potentially damaged in harsh weather, if they are pruned too early.
How to prune
Lacecap and mophead hydrangeas like Hydrangea macrophylla "Bridal Bouquet" flower on old / last season's wood - so you just need to deadhead them while keeping the main branch structure in place. If they are in pots, you can hard prune them to keep them to a good manageable size, and in a nice overall dome shape. Plus it is good to then clear away any dead, spindly, crossing or crowded stems. Always prune down to just above a pair of strong juicy buds.
Other kinds of hydrangeas like Hydrangea paniculata "Limelight" and Hydrangea arborescens “Annabelle” flower on new wood – new spring growth. So you can prune them almost / down to the ground. With Hydrangea paniculata "Limelight", it is a good idea to establish a basic framework of 3-4 strong stems approx 30cm tall in the early years - and then prune back to this low framework every year. This will produce blooms on sturdier stems.
Feeding & watering
Like Roses, Hydrangeas like a lot of food and water, to keep their beautiful large blooms going. Feed every 3 months, starting at the same time as your late winter prune, then feed again in late spring, and after Xmas holidays in February. Use Triabon or Nitrophoska for plants in pots; and Biophos for Hydrangeas in the ground.
Water as needed throughout the season. They will definitely need watering generously every day or 2 through mid summer especially if they are planted in pots. You will be able to easily see when they need a water, when their flower heads droop.
A word on colour
Hydrangeas come in 3 basic colours: blue, white and pink.
Whites will always be white, and generally need a bit more shade to avoid sun burn and to prolong their fading blooms into autumn.
Otherwise, Hydrangeas will turn blue in acid | clay based soil; and pink in alkaline | limestone | peat soil.
You can change or intensify their natural colour by adding:
Aluminium Sulphate to blue variety Hydrangeas to make them bluer
Lime to pink varieties make them pinker.
It is better to add a little of the colour changer, 2 or 3 times during the growing season per directions, than a lot at once, to avoid burning the roots. The growing season is spring & summer.
Note: Hydrangeas generally flower pink in potting mix, even though they may be a blue variety, because potting mixes in general do not contain the blue activating ingredient aluminium. Over time you can turn your Hydrangeas blue in pots, by regularly adding Aluminium Sulphate.