We are in the process of listing and adding an image for all our plants. All photographs will be taken in the Derby collection. The plants in the ‘National Collection of Paniculata’ will have an added profile to describe the individual plant in fuller detail. Although some of the plant descriptions are quite brief, we intend to provide more detailed descriptions when we have studied each cultivar in detail.
Click on any species and you will be presented with a list of all the cultivars for that species that are in our collection, along with a thumbnail photograph in most cases. Clicking on a cultivar will give more information and access to a larger photo.
Genus, Species and Cultivar.
Hydrangea is the family name or genus.
Within this genus are about 75 species. We hold the only national collection of the paniculata species. Our macrophylla and serrata collections are larger than most gardens in UK. We have a fair collection of arborescens, climbing varieties, aspera and heteromalla.
Within the species are cultivars. These have combined DNA which is either mixed in the wild or assembled deliberately to isolate a particularly advantageous trait.
Hydrangeas have been popular garden plants for a long time and although there are only around fourteen species in general cultivation plant breeders have been busy over the years producing over a thousand different cultivars. The purpose of national collections is to preserve this huge variety of cultivars as some go out of fashion or are no longer propagated and stocked in nurseries.
Flower Head Types
There are three main flower head types in hydrangea:
- The flat topped ‘corymb’, typical of the lacecap forms of Hydrangea macrophylla.
- The long cone shaped ‘panicle’, typical of Hydrangea paniculata and Hydrangea quercifolia
- The ‘globe shape’ of flower heads formed from either a corymb or panicle that has been bred to minimise the number of fertile florets in the flower head and maximise the number of showier sterile florets.
In the typical wild forms of hydrangea, the centres of the flower heads (inflorescence) are packed with small, plain and often dull coloured fertile florets. These are surrounded by sterile florets that do not have any stamens or carpels. These sterile florets usually have large showy and often brightly coloured sepals. To avoid confusion, we are using ‘floret’ to describe the tiny fertile and sterile components of the inflorescence and ‘flower head’ to replace inflorescence.
It is of no surprise that plant breeders have tried to breed forms with more sterile florets than fertile florets. When the fertile florets are eliminated from the flower head, it turns naturally into a globe shaped.
Pink and blue Hydrangea macrophylla react to the acidity or alkalinity of the soil. Acid soil produces blue flower heads and alkaline soil produces pink flower heads. We have found changing the soil type is expensive and unreliable. Deep red and white macrophyllas aren’t affected. The flower heads of the other species are also unaffected.
Hydrangea paniculata and arborescens can be pruned after flowering because they flower on new wood. Arborescens will perform better if pruned down to the ground. The lower paniculata are pruned, the larger the flower heads will be.
All other hydrangeas flower on the previous year’s growth. Pruning that growth at the end of the season will mean that it won’t flower the following year. A few may flower again at the end of a long Summer when the wood has hardened. A new range of ‘everlasting’ macrophyllas is available which are bred to flower on new wood and continue to produce flower heads throughout the season.