Hydrangeas are top performing; tolerant, easy to grow plants that will reward you with an abundance of blooms even if you do nothing other than love them and leave them. However if you want to get the very best from Hydrangeas follow our simple "How To" guide and you will maximise the full potential of these beautiful flowering shrubs.
Most of the Hydrangeas grown in N.Z. are Hydrangea macrophylla (macro = large, phylla = leaves) cultivars; these are usually described as "Mop Heads" or "Lace Caps". There are also climbing Hydrangeas available along with cultivars of Hydrangea quercifolia, H. paniculata, H. aborescens and H aspera.
Situation - Hydrangeas grow best in dappled shade. At the very least they should be planted with protection from the afternoon sun. The exception to this rule is Hydrangea quercifolia which is quite happy to grow in a sunny spot.
Soil - Hydrangeas are very tolerant of soil conditions but prefer a soil that is humus rich which does not completely dry out in summer. The colour of Hydrangea flowers can be affected by the acidity or alkalinity of the soil. Acid soil = blue flowers, Alkaline soil = pink flowers. On average N.Z. soils are slightly on the acid side meaning Hydrangea flowers will tend to be bluer rather than pink. Acid soils can be treated with Lime to make them more alkaline, alkaline soils can be treated with acidic fertilizer to make them more acid. Alternatively blue flowering Hydrangeas can be side-dressed with Aluminium sulphate during the growing season to intensify the blue colour of the flowers. White flowering cultivars usually remain white regardless of soil type. Don't worry, if you do none of the above your Hydrangeas will still grow well and produce flowers.
Water - Never let your Hydrangeas completely dry out in summer. They are big lusty plants and appreciate a deep watering at least once a week if there has been little or no rain at this hot time of year.
Feeding - Side dress with a well balanced slow release fertilizer in late spring or if you prefer liquid feed every few weeks in the rapid growth period.
Cultivation - No particular cultivation methods required.
Pruning 1 - The first rule of Hydrangea pruning is it doesn't matter if you don't prune your Hydrangeas, they will still flower.
The second rule is that they are the easiest of plants to prune as the stems have obvious fat buds to guide you to where the cut should be made.
Hydrangea macrophylla (Mop Head and Lace Caps) flower on second year wood. That means the flowers will appear on the stems that were produced the previous season. In N.Z. the preferred time to prune is late autumn-early winter. If you live in a particularly frosty area then it pays to prune towards spring leaving the spent flower heads on the plant to act as protection. When pruning keep in mind that the more you cut off the less flowers you will have the following summer. Cut back to a pair of fat buds with sharp clean secateurs. Completely remove any dead or crossing branches as required.
Alternatively if you cannot stand the sight of spent flower heads and can't wait to give your Hydrangeas a haircut then you can do your pruning in summer immediately after flowering. This will allow the plant to produce new flowering wood/stems before winter dormancy.
Light dead-heading can be done at any time - this is not the same as pruning.
Pruning 2 - Hydrangea paniculata and Hydrangea aborescens cultivars such as "Annabelle" bloom on new wood/stems and are usually hard pruned in late winter - early spring to encourage new stems that will flower the same season they grew.
Climbing Hydrangeas - seemannii and petiolaris only need light dead-heading and it is the same with Hydrangea aspera and quercifolia.
Wairere Nursery 826 Gordonton Road, R D 1, Hamilton Ph: (07) 824 3430 Email: Open 7 days 8:30am-5pm