5 Festive Facts about Holly

Dr Trevor Dines

Dr Trevor Dines

Plantlife Botanical Specialist

15th December 2017

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Credit: Andrew Gagg/Plantlife

1. Giraffes would find it easier to eat holly leaves...

Holly is well known for its tough, spiny leaves; the long, needle-like spines are a very successful deterrent to browsing animals. But look high up in a holly tree canopy and you might notice the leaves are less spiny. Unless giraffes are wandering around our countryside, fewer spines are needed high up. Most spines are produced lower down were sheep, goats, cattle, horses and deer are likely to browse the leaves.

2. If a bush has berries, it's female...

Holly is dioecious (from the Greek for “two households”), meaning that each individual holly plant is either male or female. Bushes of each type are needed nearby for cross-pollination to guarantee berries, so bushes laden with berries at Christmas are always female, while those without might be male or a female that’s growing in isolation. Confusingly, the garden variety Golden King is female, while Golden Queen is male!

3. Holly bushes control how and when its berries are eaten...

The bright scarlet berries attract many birds, especially thrushes including blackbirds, fieldfares, redwings and mistle- and song-thrushes. In autumn and early winter the berries are very hard and bitter due to mildly toxic compounds including saponins, flavonoids and cyanogenic glycosides. As winter continues, hard frosts break down these chemicals eventually making the berries palatable in late winter and early spring, when hedgerows are otherwise largely bare. But even now the berries retain some toxicity, so birds eat just a few on each visit. Frequent visits are therefore needed and this aids dispersal of seeds, with a few seeds deposited in droppings in lots of different places over a long period of time.

4. Unlike other native shrubs, holly leaves are very tough and unpalatable to insects...

Holly leaves provide food for just 29 species of insects, compared to nearly 200 for hawthorn and over 260 for blackthorn. The insects that do feed on holly include the beautiful holly blue butterfly, whose caterpillars feed on softer parts like flowers, young berries and young leaves. For some reason, female plants are preferred. Holly leaf miners feed for much longer on each bush. As new leaves unfurl in April and May, female leaf miners lay their eggs on the underside of leaf stalks or the base of the midrib. The larvae feeds within the midrib, moving towards the leaf-tip, until January, when it emerges into the leaf blade and makes its familiar tunnel through the centre of the leaf. Adults emerge the following May or June.

5. Holly is well known for its ability to deter evil spirits and witches...

This may come originally from its evergreen nature; when all else in the winter wood appeared dead and lifeless, holly remained green and full of berries, giving hope for new life in the spring. In the depth of winter, sprigs of holly were often brought in the home because of this, and thus to ward away evil. It became bad luck to cut down a holly tree (a sentiment that persists to this day) and in some areas holly bushes were allowed to grow up through hedges to prevent the movement of witches, who apparently love to run along hedge-tops.

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