FAQs Hydrangeas

Hydrangea are a high performing yet rather undemanding deciduous shrub. Although they were a little out of fashion for a while, being considered a little “common” and a bit “nana-like.” However, these gorgeous gals have made a resurgence; they are a hot item on the export cut flower market and have deservedly earned the respect from a new generation of gardeners.

Hydrangeas are super simple to grow and will adapt to most conditions, but they will perform at their best when given a bit of afternoon shade and plenty of water when it is hot and dry in the summertime. Most Hydrangeas grown in New Zealand are varieties of Hydrangea macrophylla (large-leaved), often referred to as Mop Head or Lace Cap. The colour range includes shades of white, cream, blue, pink or purple.

We’re here to help you grow your best hydrangeas. We’ve collected a list of commonly asked hydrangea questions. Read our FAQs on hydrangeas below:

How to prune your hydrangeasPruning a hydrangea - FAQs hydrangeas

Alison asked: My hydrangeas will not flower. I pruned them at the right time and maybe gave them too much fertilizer. They are the mop top variety. Is there a special way to prune them because if I don’t, they will be reaching the top of the house next year.

Our answer: Mop top Hydrangeas bloom on old wood (the stem that produced flowers the previous year)so if you pruned them this year there is a chance you may have pruned off all the stems that were about to produce flowers. You can leave them all together now and they will produce flowers next year but if you want to reduce their height which it sounds like you do, you may have to forego some of the flowers for a season.

The best time to prune your Hydrangeas is late winter or even early spring in case there are any late frosts which might affect the buds.

  • Prune back any damaged or dead stems (right back to the base)
  • Prune any weak or spindly growth (right back to the base)
  • Cut out any branches that crossover
  • The remaining stems – Choose how big you would like your plant to get and then prune back to where you can see two big buds together on a stem, these will be flower buds and will produce flowers. If there is none prune back to the single smaller leaf bud. These will not produce flowers this season.

A helpful link for you: https://www.palmers.co.nz/how-to-prune-hydrangeas/

How to colour your hydrangeas

Philippa asked: What do you feed hydrangeas to keep their pink colour?

Our answer: The reason pink blooms often turn blue has to do with the pH levels in the soil. To keep blooms pink the soil needs to be more alkaline than acidic. Adding lime to the soil will help heighten the pH levels in the soil. Add the lime sparingly and make sure it is well diluted as using too much can harm your plants.

Hydrangeas not blooming

Katie asked: I have these great hydrangea bushes, but unfortunately they haven’t blossomed these recent years. So, this spring I’ve watered it heaps, and have added some fertiliser, and a couple of their leaves have started turning yellow, should I be worried? And do you have any advice to make hydrangeas blossom again?

Our answer: There are several reasons why your hydrangeas may not be blooming. The most likely reason is that you pruned at the wrong time and chopped off the flower buds. Late spring freezes could be another reason. If a late spring freeze kills flower buds that formed the previous summer, you won’t get to savour beautiful blooms this growing season. Repeat blooming types can overcome buds lost to a late freeze because they also form flower buds on new stems. Another reason gardeners wind up with no flowers on hydrangeas is usually due to their hydrangea getting a lack of sunlight. If plants are tucked into too much shade, few flowers form. French and lacecap hydrangeas need at least three hours of sun to stage a strong flower show. Too much nitrogen fertiliser can also result in hydrangeas not flowering. When nitrogen fertiliser, especially from lawns, keeps washing into soil around hydrangeas, you can wind up with full plants covered with deep green, healthy leaves, but few flowers. Make sure that lawn fertiliser isn’t landing on hydrangea planting areas. If none of these conditions apply to you and you still have no flowers on your hydrangea, you may be trying to grow it in too cold of a zone. Some hydrangea shrubs can survive winter in a too-cold zone, but they will never flower because the cold kills the blossom buds.

Can you keep them inside?

Jan asked: I have three hydrangeas in pots and have them inside. Maybe this is not a good idea but they look good where I have got them. They are not looking their best, they have brown leaves and leaves falling off. Maybe I have watered them too much or maybe they don’t like being inside?

Our answer: It is not ideal to keep Hydrangeas inside for a long period of time. You may get away with it for now, especially while it is in its growth stage and blooming and looking fantastic! But they do require a period of dormancy in winter that is brought on by our colder weather. Hydrangeas are also prone to drying out very quickly indoors as our houses can warm up very quickly in summer.

My advice would be if you want to keep the Hydrangea inside while it is in full bloom as I am sure it makes quite the statement. Place it in a cooler room within the house but also so it gets a decent amount of sunlight. Do not let it dry out but also don’t let it sit in a saucer of water. Make sure the water can drain away after watering. The leaves turning brown and falling off to me indicates a watering issue so either it is not being drained away or perhaps not being watered enough.

Feeding regularly with a liquid fertiliser may help give it a boost of nutrients whilst it is indoors.

Brown spotsBrown spots of hydrangea leaves - FAQs hydrangeas

Sarah asked: How do I get rid of brown spots on hydrangea leaves?

Our answer: It is quite normal for Hydrangeas to have spots on their leaves at this time of the year. It is a sign of stress, to prevent this use a good Mulch to prevent temperature changes and keep an even moisture content. Use a liquid fertiliser (Seaweed, Compost tea, Fish fertiliser) to keep the plant healthy.

Green hydrangea flowers

Hayley asked: We moved to a new house 18 months ago and the first summer the white hydrangeas were beautifully white, this last summer they have been more green. They had a good prune. What to I need to do to do to maintain the white colour?

Our answer: Apply sulphate of potash 2-3 times per year (now until late spring) and the colour should change back to white.