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What is a Holly?

What is a Holly? | Copyright GreenPlantSwap Ltd

“The Holly and the Ivy, now they are full well grown: of all the trees that are in the wood, the Holly bears the crown”

So runs the familiar carol, and although Ivy doesn't get much of a look-in, certainly in the middle of winter the Holly, with those glossy, spiny leaves and glistening red berries, could easily be seen as the “king” of the wood.

For the rest of the year, Holly is a slow-growing shrub or small tree with evergreen leaves, which means that they stay green all year round. Many people assume that evergreens don't drop their leaves but in fact they do – they just do it gently, all through the year, instead of losing the leaves in one mad rush at autumn time. If you look under any Holly tree, bush or hedge, you will find a dense layer of dead, but still spiny leaves which remain in place for years, refusing to rot, and providing a safe, dry understory for vast amounts of insects and small mammals, including hibernating hedgehogs.

In the wild, Holly can be found as an understory in mixed deciduous woodland, usually as low-growing gangly bushes; or in more compact form as part of the hedgerows, where self-set Holly seedlings grow up to strengthen the hedge, and to provide year-round cover for birds.

It also appears, less often, as individual trees, which can grow to 15m in height: there used to be a superstition that it was unlucky to cut down a Holly tree, which could account for the number of lone trees standing isolated in the middle of an otherwise arable field. These trees can be very long-lived, as long as 500 years, but a mere 100 years is more usual.

And what of those spiny, prickly leaves? Why are they so spiny? The spines developed as a mechanism for preventing grazing, particularly as, being evergreen, the Holly will have leaves to offer when there is little else around for grazers to eat. Tender new leaves have greater spinescence (and isn't that a lovely word? Well worth saying out loud) to protect them, the leaves growing less spinescent as they increase in size.

The botanical name for the true Holly is Ilex, and this is the only surviving genus in the family Aquifoliaceae. Within this one genus are over 400 species, though not all of them are evergreen, and not all of them have shiny, spiny leaves: many cultivated forms have been bred with reduced spines, or no spines at all, to make them more acceptable in a garden setting, or have been bred for variegated foliage.

Most species of Ilex have only male flowers on one individual plant, and only female flowers on another. This is called “dioecious” in botanical terms, and it literally translates as “two houses” - one house for male, one for female. Most people who choose to grow Holly want it for the berries, as well as for the leaves, so it is important to select female plants to get the berries, although at least one male plant will be needed to fertilise them. Usually, a ratio of one male to five female plants will result in good coverage of berries.

Ilex x altclerensis 'Golden King' photoDetermining the sex of Hollies is not always easy, particularly when their names mislead! This Ilex hybrid 'Golden King' is in fact female; while Ilex aquifolium 'Golden Queen' is male. A bit of mischief perhaps with cultivar naming!

It can be tricky to work out which plants are male and which are female, particularly as some of them are very unhelpfully named: the cultivar 'Golden Queen' is a male variegated form, and 'Golden King' is – yes, you've guessed it, a female form. The only way to be sure is to wait until May or June then look closely at the flowers, which are small, white, four-petalled, and appear in small clusters along the shoots, in amongst the leaves. How to tell the difference? Male flowers have four stout, pollen-tipped stamens around the dark brown centre of the flower, which looks rather like a Phillips screw-head. Female flowers have rather weak, feeble stamens without any pollen, and the centre quickly becomes domed and bright green – this is in fact the nascent berry. Male flowers are also slightly scented.

Why are they called Holly?
It is not clear where the common name originated: there is a Middle English word holis "[dwelling by] Holly trees" but this does not really explain the meaning of the word Holly. Some people suggest it is a corruption of “holy” and point to the pagan associations of the plant.

The botanical name for the classic English Holly Ilex aquifolium is easier - ‘folium’ is Latin for ‘leaf’, and the ‘aqui’ part might have originated from ‘aqua’, which means ‘water’ - perhaps because the shiny leaves appear to be always wet. Certainly, the word ‘aquifolium’ or 'aquifolia' itself is used as a species name in a number of genera where it means ‘looks like Holly’. And as for Ilex? There seems to be a rather circular definition, where ‘Ilex’ comes from ‘Quercus ilex’, the Holm oak, because Holly looks like Holm oak: but ‘Quercus ilex’ is so named because the Holm oak looks like Holly. Confused? We are, too. ‘Holm’ is an archaic word meaning ‘island in a river’ so it may be that this was where the plant was first found but there again, the Latin for ‘island’ is ‘insula’, which could possibly be corrupted into Ilex. We shall never know for certain.

Quercus ilex photoWhich name came first, Quercus ilex, the Holm oak, or Ilex, the Holly? It's hard to say.

Holly has been a popular girl's name since Audrey Hepburn starred as Holly Golightly in Breakfast at Tiffany's. According to the book, the name was short for Holiday, rather than referring to the plant, but the shortened form is the one which is still popular now, particularly for babies born around Christmas-time. Despite being the name of a sturdy, prickly plant, the name has never really caught on as a male name, and these days is almost exclusively female.

What is Holly used for?
Holly, with red berries, is a familiar symbol of Christmas, despite both leaf and berry being extremely poisonous. The Pagan associations of Holly go back for centuries – it has long been used to decorate homes in winter, being seen as a charm against witches, goblins and the devil. In pagan ritual, Holly symbolised the male god, who could carry life through the winter, as demonstrated by the evergreen leaves, with Ivy being the counterbalancing female god.

The wood of the Holly tree is not strong, or particularly durable, but it does have a very uniform structure, with hardly any visible grain, and is a very pale, nearly white colour, which makes it much in demand for decorative work such as inlays, or for use in wood-turning for small items. Conversely, it can also be dyed very easily and evenly, so it is often dyed or stained black, then used as a substitute for ebony in such things as piano keys and chess pieces.

The close grain means that the wood can be carved in great detail, and in the days before moveable type was invented, it was used by printers: the engravers would painstakingly carve a reverse image into a block of Holly wood, which would then be inked and pressed onto paper. Rather like the potato printing we did when we were children, but much better quality.

It is also used to make walking sticks, and if the wood carving goes wrong, all is not lost as it makes excellent, hot-burning firewood.

Ilex aquifolium ‘Pyramidalis Aurea Marginata’photoThere are many variegated Ilex that will give good year-round shape, screening and colour to the garden, as well as leaves and berries for indoor decoration in winter (photo: Ilex aquifolium ‘Pyramidalis Aurea Marginata’).

In the garden, Holly makes an excellent decorative or burglar-defying hedge and, being evergreen, can add privacy as well as security to a boundary. It is easy to maintain, as it is comparatively slow-growing, and if you clip it every year, it becomes dense and impenetrable. The berries are an added bonus, and the rather gappy internal structure not only makes it ideal as a windbreak (this might sound counter-intuitive, but the wind can blow through the gaps, being tamed on the way, rather than pushing the plants over) but it also makes it a wonderful safe haven for small birds. Even if you have a normal mixed hedge, look closely, and you might well find some self-set Holly infiltrators, as the seeds are often dropped by passing birds and can become part of your hedge without you even noticing.

Grown as a specimen tree, Holly is perfect for smaller gardens, as it grows slowly, and can be trimmed or pruned if it outgrows the allotted space. There are many variegated cultivars, as well as plenty of plain green ones, and if you choose a female plant, and have a few other Hollies nearby – perhaps as part of a hedge – then you can expect berries as well as leaves. But if you want some for winter decorations, you might have to cut a few branches in early December, standing them in a bucket of water somewhere cool and out of the way, as the birds will strip the berries as soon as the weather turns cold.

How do you know it's a Holly?
Traditionally, Holly is recognised by the spiny-edged, shiny green leaves, although not all Holly is spiny, and not all spiny-leaved plants are Holly.

The leaves are held alternately on short, thick petioles (stalks) and are glossy green above, slightly duller green below, with those familiar strong prickles at the margin, and a slightly lighter veined mid-rib. The leaves have crazily-undulating margins, such that some of the spines point upwards, and some point downwards, as well as some pointing outwards.

The newer shoots, at the ends of the branches, are green, sometimes with a purple tinge, while older ones become brown.

When allowed to grow unchecked, Holly can form a dense, handsome, conical tree, whose branches tend to arch downwards then sweep upwards at the very tip: but in woodland it is more often found as a tangle of rather thin, gangly branches, due to the lower light levels. It frequently produces suckers, which grow into thickets of thin growth.

There are 176 plant records featuring the word Holly in the GreenPlantSwap Plant Finder, and only 102 of those are Ilex: unsurprisingly, many of the other 77 have spiny-edged leaves which make them “look” like Holly, even though they are not related. Many of them have the species name ilicifolia: “folia” being Latin for foliage, and the “ilici” part being derived from Ilex. These include the Holly-leaved sweetspire, Itea ilicifolia; Holly-leaved cherry, Prunus ilicifolia; Maori holly, Olearia ilicifolia and the Holly flame tree, Chorizema ilicifolium.

Mahonia aquifolium have compound leaves, but the leaflets do a good impersonation of Holly's pricklier leaves, hence the common name Holly-leaved barberry; as do some of the Osmanthus species, which are variously known as Chinese holly, False holly, or Holly olive, a name which really trips off the tongue.

As well as these, we have some imposters: White holly, Pittosporum undulatum, whose leaves are barely crinkly; through Summer holly, Comarostaphylis diversifolia, which looks nothing like Holly at all: right up to New Zealand holly, Olearia macrodonta, whose leaves are prickly enough to please any Ilex fan.

Eryngium giganteum photoEryngium giganteum, the Sea Holly - a highly decorative and decently prickly shrub with bluer green leaves than the true Holly.

Talking of imposters, the genus Cyrtomium are known as Holly ferns, or Japanese holly ferns, and they are not even shrubs! Their fronds are pinnate and have slightly wavy margins, but it is quite a stretch to imagine them as “holly-like”. And then we have the herbaceous Eryngium or Sea holly, whose matte leaves are at least decently prickly, but which are usually blue or blue-grey in colour, a long way from the clear dark green of our Ilex. There is even an underwater “holly” - Holly-leaved naiad or Najas marina, an aquatic plant with vaguely undulating fronds.

Lastly, we have to allow Quercus ilex, the Holly-leaved oak, into the club, as it is a tree, and it does indeed have prickly, evergreen, shiny-on-top leaves, although it is easy to tell the difference between Oak and Holly, as the Oak leaves are dusty white underneath.

Types of true Holly
Common holly, English holly, European holly, Berry holm, Aunt Mary's tree, Poisonberry, Christmas tree, Christ's thorn: all of these are common names for Ilex aquifolium, the familiar Holly.

Cultivars include 'Albomarginata', 'Argentea Marginata' and 'Aureomarginata' which have varying shades of variegation on the leaves. 'Pendula' is a female form which, as the name suggests, has a weeping habit. 'Ferox' or Hedgehog holly has leaves with spines on the upper surface as well as along the edges of the leaves, making it decorative, but perhaps the prickliest of all!

Ilex aquifolium 'Ferox' photoIlex aquifolium 'Ferox' - the utterly intruder-proof Hedgehog holly, with spines on the upper surface of the leaves as well as the edges.

Though most of these hollies produce the familiar red berries, Ilex aquifolium 'Bacciflava' has orange-yellow fruit.

Highclere holly, Ilex x altaclerensis is a very popular species, it is a cross between Ilex aquifolium and Ilex perado and it is a more vigorous grower than either parent, with larger, less spiny leaves, and again there are dozens of wonderful cultivars for garden use.

Chinese holly, Ilex cornuta, has large red berries, larger than those of Ilex aquifolium, and larger, rather rectangular leaves.

Japanese holly or Box-leaved holly, Ilex crenata, has comparatively small leaves, with hardly any toothing to the margins, which makes it much in demand as a replacement for blight-hit formal Box hedging, and for specialist topiary, in particular for what are called “cloud-pruned” forms, where individual branches have pom-poms of foliage. These 'hand crafted' slow-growing trees are hugely expensive to buy and require immense patience to grow to any substantial size. lf left unclipped, they produce black berries.

alt text hereThe potentially very shapely Japanese holly, Ilex crenata, which has suitably small leaves for cloud-pruning ... and black berries when left unclipped.

As does Inkberry or Appalachian tea, Ilex glabra, another non-spiny member of the Holly family: slow-growing and rounded in shape, this shrub is mostly used for decorative purposes, although apparently the Native Americans used to brew a hot drink from the berries, which is quite surprising considering how poisonous other Ilex berries are.

Back to the Christmas carol
So, if the Holly is the king of the wood, what about the Ivy? It's in the title of the carol and the first line “The Holly and the Ivy, now they are both well grown”, then is not mentioned again. Why?

Originally, Holly figured prominently in the Roman celebration of the Saturnalia, which was converted into Christmas, and Ivy was formed into wreaths and garlands for decorations during the winter months, being allied with the Roman god of wine, Bacchus or Dionysus.

These two were absorbed by the new Christianity, despite resistance by church officials, and the use of greenery for indoor decoration became an immutable part of the Christmas celebration.

The carol was written in the 17th century and was based on earlier songs, as is traditional with any folk song - “sampling” is nothing new - and those earlier songs, which perhaps dated right back to medieval times, featured the rivalry between men and women, thinly disguised as a contest between the Holly and Ivy. In the wild, Ivy is often found winding its way up the stems of Holly in hedgerows, and this would be a familiar concept for the mainly rural peasantry of the time. The audience would recognise the competition of the two plants, and they would all be familiar with the plant symbolism of the time, with Holly seen as being masculine, probably due to the rigid stems and prickly leaves; while the softer leaves and accommodating stems of ivy were associated with the feminine.

Apparently the writer of the carol just decided that women were not important any more, and wrote them out of the carol! Or perhaps they just couldn't find any aspects of the Ivy to fit in with the rather strained symbolism of the verses? Or maybe there were originally another set of verses, detailing the religious aspects of Ivy, which have been lost over time – we will never know!

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