Ho ho ho... it’s time to get to know holly!

Peter Dowdall celebrates the prickly berried plant that takes centre stage at Christmas —and its relatives.

We all like to overindulge at Christmas — it’s a time to kick back, put the feet up and enjoy too much of a good thing.

It’s all about traditions at this time of the year, and from a gardening point of view, the most important is berried holly. We use it in wreaths, garlands and simply in vases about the house. The bright red berries contrasting so vividly with the dark green foliage make it one of the foremost symbols of the festive season in this part of the world. And, as you are settling down to enjoy a plate piled high on Christmas day, so too for the birds, who will be tucking into a feast of Holly berries.

Holly or Ilex. to give it its botanical name. is a genus of nearly 600 species mostly evergreen but some deciduous. The species that is normally grown for winter berries is Ilex aquifolium, the prickly-leaved classic Holly. The role that this plant plays in the biodiversity of your garden cannot be overstated. The berries are loved by many birds as well as other wildlife and the spiny evergreen foliage provides safe refuge for birds during the winter, the thorny leaves providing protection against predators.

The mistle thrush, normally a social bird, will gather in groups and will feed together early in the season, but as soon as the holly berries appear, all that changes. They will set off in pairs and claim trees as their own. They may not need the berries but they will protect their tree from other scavengers as if their lives depend on it and indeed they might if the winter gets cold enough and food gets scarce. If you see a holly bush laden with berries while all around are bare, there’s a fair chance you will find mistle thrushes nesting.

Ilex aquifolium is a dioecious species, meaning that male and female flowers are produced on separate plants and this is true of most hollies but not all. JC Van Tol for example is a self fertile variety with one plant producing berries freely with foliage that is shiny dark green but without the prickles that you get with Ilex aquifolium. ‘Nellie Stevens’ on the other hand produces berries parthenogenetically, meaning that the berries are produced asexually with no fertilisation taking place.

If you’re ever stuck trying to remember the names of male and female forms just remember how funny we horticulturists and taxonimists are — so funny in fact that the name of the male holly is ‘Silver Queen’ and the female form is ‘Golden King’. A sample of the sense of humour to be found among the anoraks.

For a genus that can trace its roots back over 82 million years it is very worrying to learn that the aquifolium species is now at risk of making the list of endangered plant species. The Holly Leaf Miner can attack and leave brown mines through the leaves and brownish patches on the top of the leaves — unsightly, but it doesn’t do serious damage to the plant.

The Holly Leaf Blight, however, is a serious problem leading to blackened leaves and stems which can result in near total leaf drop and the demise of the entire plant. As with all fungal infections I would advise cultural control, in other words cutting out all infected growth and stems and ensuring no diseased material is left around the base of the plant. There is no chemical control available for Holly Leaf Blight as it is a form of Phytopthora illicis. However treating the soil with Bordeaux Mixture may help.

‘Ferox Argentea’ or Hedgehog Holly is a really special form — its common name referring to the fact that most leaves have a cluster of prickles on the topside of the leaf and not just around the outside of the leaf. The dark green leaves are surrounded by a creamy yellow margin and it will develop into a substantial sized shrub.

Not all hollies are evergreen, Ilex verticillata is a deciduous form which produces masses of bright red berries on naked stems. Commonly known as Winterberry and native to North America and southern Canada it’s not widespread in Ireland which is a pity because the winter display it gives is second to none.

It is such a large genus some Ilex look nothing like what you and I would refer to as holly. Ilex crenata for example is a very slow growing, dense evergreen shrub which is often grown as a hedge instead of, and often mistaken for Buxus or Box hedging.

Ilex crenata ‘Convexa Gold’ and ‘Gold Gem’ will make a welcome addition to any garden with golden foliage and dwarf habit making them ideal choices for small rockeries or ground cover areas. One further advantage of these two varieties is that they will thrive in a north facing shaded area.