How to Grow Hydrangeas

Plant Types

There are many different hydrangeas to choose from which are available in different flower forms and types.

There are three different flower forms:

• Mop-Head
• Lacecap
• Paniculuata

Which are available across two different plant types:

• ‘Old Fashioned’ – Old fashioned hydrangeas are unique as you can change the colour of the flowers with the PH of the soil. Old fashioned hydrangeas come in Mop-head or Lace Cap flower forms.
   
• ‘Modern’ Hybrids – There are a wide range of Modern hybrids in new flower and foliage types. Some even come with coloured stems. Modern hybrids remain true to colour and don’t change with soil PH.

Timing

Hydrangeas are best planted from August all the way till Christmas.

Location

They do well in full sun or part shade but tend to flower longer in dappled light. Avoid hot, dry, exposed spots.

Hydrangeas don’t like competition, so give them plenty of room.

Soil

Hydrangeas like good, rich, fertile soil. Add lots of organic matter and sheep pellets when planting.

Changing colour of hydrangeas

It’s important to know what you’re planting because with Old Fashioned hydrangeas, you can actually change the colour of the flowers.

• The flower colour is determined by PH levels in the soil.
• Use a soil testing kit, available from Mitre 10, to check the levels of your soil.
• Low PH level means acidic soil, high PH means alkaline. Blue likes acidic and pink likes alkaline.
• Add aluminium sulphate for deep blue shades, and dolomite lime for bright pinks.

Planting

• Dig a hole twice as wide and deep as your plant’s pot.
• Add compost and mix in.
• Mix in sheep pellets.
• If you’re planting an Old Fashioned hydrangea, add any aluminium sulphate or dolomite lime, depending on what colour you want your flowers to be.
• Soak plant in seaweed tonic to reduce transplant shock.
• Ease plant out of container.
• Place in hole.
• Add more sheep pellets and compost and mix in the soil back into the hole.
• Press down firmly.
• Add a layer of mulch.
• Water in.

Flowering

Hydrangeas can be sensitive. Poor flowering could be due to too much shade, if you haven’t pruned correctly, or if the weather has been volatile.

Watering

Hydrangeas are very thirsty when flowering. Water in the morning from the base to avoid disease, and make sure you do it often and deeply.

Feeding

Hydrangeas grow best if they are fertilised once or twice in the summer. Give them a good slow release fertiliser like nitrophoska blue in spring, and again during flowering.

Pests & Disease

• Keep an eye out for powdery mildew, especially in humid weather. You can spray a fungicide to treat this, or remove affected leaves.
• Rarely targeted by insects. If there are any problems, an oil based spray like conquer oil should sort it out. Make sure that you spray in the evening to reduce the chance of leaf burn.

Pruning

• Deadhead them throughout the year by removing spent flowers.
• Hydrangea’s are fast growing and need a hard prune once a year in winter to keep them nice and healthy. Use the shortest day of the year as an easy reminder.
• You should prune up to 50% of your Hydrangea bush each year to reinvigorate the plant and keep it compact. This keeps the flowers upright and stops them getting too top heavy. This amount of pruning may seem extreme, but you’ll be amazed how quickly they bounce back.
• Prune out any dead, damaged, or diseased wood back to a decent-looking bud. Be careful not to damage these buds as they should form flowers during the next season. Cuts should be made at a 45° angle sloping away from the bud.