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What is a Fir?

What is a Fir? | Copyright GreenPlantSwap Ltd

One of the true Firs - Abies koreana

A Fir is an evergreen tree, which every child can draw instantly and accurately – just give them a green felt pen and say “draw me a Christmas tree, please”.

They are chosen for this festive use because they are fast-growing, and have dense, regular, symmetrical growth right up to the tip, along with smooth, leathery foliage which doesn't hurt the hands, which smells nice, and which takes a long time to die and drop from the tree.

Simple as this sounds, the common name ‘Fir’ is common indeed. There are 179 plants or trees in our Plant Finder with these three letters. However, the term is particularly applied to several different types of conifer – or ‘cone-bearing’ – tree; and they are best distinguished by their botanical names, which identify each one uniquely, as they have varying characteristics.

True Firs
The true Firs are considered to be those in the Abies genus, pronounced Abby-ezz. We have 38 Abies trees in our Plant Finder.

When people say Fir they usually mean the group of Abies conifers called Silver firs, but there are also Korean firs, Noble firs, Balsam firs, Greek firs , White firs, Subalpine firs – all common names of trees within the Abies genus. Then just to confuse things, there are Douglas firs which are not Abies or true Firs at all. They belong in the genus Pseudotsuga, one of the more notably unpronounceable plant names.

Abies belong to the Pinaceae or ‘pine’ family, but they don't have the long thin needles that you might associate with that name: instead, they have flat, linear leaves which, if you look very closely, have a groove in the top surface, and – mostly - a tiny notch at the tip of the leaf.

The leaves are usually arranged with a parting underneath the branch, as though someone has neatly combed them to each side, which makes them easy to differentiate from that other popular Christmas tree, the Spruce, whose leaves usually stand out bushily all round the branch.

Spruce is the common name of trees in the genus Picea, which are also conifers, but not true Firs. Spruce have rough bark, while on Firs it’s smooth; and a Spruce needle will roll more easily between your thumb and fingers, because they are 4-sided, while fir needles being flat will not.

Silver fir leaf photoSilver firs have two silvery stripes on the underside of the leaf. These are tiny pores through which they breathe.

Why are some called Silver firs? Because most of them have two silvery stripes on the underside of the leaf. These are called stomatal bands: they are bands or stripes made up of stomata, which are tiny pores through which the leaves breathe. Most Abies species have leaves which are green on top, but some of them have these stomatal bands on the top as well as the underside of the leaf, giving a very silvery appearance to the foliage.

What are Firs used for?
In the wild, Fir trees grow in the northern hemisphere, from the Arctic circle down to just below the equator. They like growing on mountains, as they are well adapted to life above the snow line: their short, stiff branches and pointed tops allow them to shed heavy snow with ease, and it is this shape that makes them so useful as Christmas trees. The three most popular species are:

Nordman fir, Abies nordmanniana, also known as Caucasian fir: they have soft glossy dark green leaves which are retained for a long time, so there is less mess on the carpet.

Nordman fir photoThe Nordman fir has longer lasting glossy dark green leaves, making them ideal Christmas trees

Noble fir, Abies procera: this one has silvery green foliage, and stiff short branches that can bear the weight of heavier ornaments without drooping.

Fraser fir, Abies fraseri: the leaves are green above, silvery below, and again, it has stiff short branches for easy decorating.

However, it is not all celebration: some species are planted in parks and gardens as ornamental specimen trees, particularly the Korean fir Abies koreana, which bears attractive purple cones even when still a young tree: but most firs are destined for our annual festival. Those which are not grown for Christmas trees are allowed to attain a much greater height – firs can grow up to 70m tall – then either converted into wood-pulp, or milled to provide ‘whitewood’ which is a soft, light-coloured wood which cannot be used outdoors, but is very popular for indoor construction as it is very easy to cut and shape.

How do you know it's a Fir?
To identify a Fir tree, you need to look very closely indeed at the way the leaves are attached to the twigs: you may need a magnifying glass or a hand-lens to really see it properly. Each leaf ends in what looks like a round green sucker, and when the leaves fall off, they leave a flat, perfectly circular scar. Firs are the only member of the Pine family to do this.

Abies grandis leaf sucker photoLeaves on true Firs are attached by round green suckers which leave a perfectly circular scar when removed. Abies are the only member of the Pine family to do this.

In common with most conifers, they produce hard, woody cones which contain their seeds. In Abies, these cones sit pointing upwards like candles on the branches, but you will hardly ever find a cone on the ground: they stay attached to the tree until they eventually shatter with age, spreading the seeds all around. When people say they have found a fir cone, they are usually wrong! (They have probably found a pine cone.)

When is a Fir not a Fir?
There are several other plants called Fir: the first is an uncommon genus of small, evergreen shrubs called Ephedra (pronounced Eff-edd-rah) which rejoices in the common names of, variously, Mormon tea, Brigham tea, and Mountain joint fir: the “tea” part relates to the fact that the stems have, in the past, been steeped in water to create a drink for respiratory problems, and the “fir” part seems to be simply because it “looks” a bit like a conifer. They are not hardy in the UK, so you would only find them in greenhouses.

Ephedra photoThe shrub that looks like a Fir. Ephedra have blueish green stems and 'cones' that develop into small, globose red fruit.

Then we have the very commonly planted Douglas fir which is not a fir at all, it belongs to the genus Pseudotsuga, so-named because at first it was thought to belong in the Tsuga genus (pronounce T'soo-ga), but as botanical investigation continued, and as science was able to bring microscopes to bear on the plants and trees around us, it was reclassified. Not quite a Tsuga, but not quite any other Pinaceae either, so it was re-named Pseudotsuga (Sue-doh-T'soo-ga). As if that wasn't hard enough to pronounce, the most common species of Douglas fir is named after a Mr Menzies (Men-zeez), and in botany, it is common to add the letter “i”, twice, after a person's name, when naming a species after them. So you have barely stopped spluttering from Pseudotsuga and then you have to cope with Menziesii – Men-zizzy-eye.

Douglas firs are different from Abies in that their leaves are attached to tiny brown cushions, instead of the round green suckers: additionally, the Douglas fir cones hang downwards from the branches. This is also the easiest way of differentiating between Abies and other things-that-look-like-fir-trees, as Abies are the only ones whose cones stand upwards. Douglas firs are plantation trees: you will normally find them in dense blocks of planting, to encourage each tree to grow tall and straight, in order to make it easy for the sawmills to process them into timber.

Douglas fir photoDouglas firs are often large plantation trees, grown tall and straight for their wood. Unlike Abies their cones hang down.

Two other conifers are sometimes described as Firs: the first is a giant of a tree, Metasequoia glyptostroboides (Metta-s'kwoy-ah glip-toe-stroe-boy-deez, which fairly flows off the tongue once you get the hang of it) or Water fir: better known today as the Dawn redwood. The name Water fir is a translation of the Chinese 'shui-sa', which refers to its ability to thrive in moist, well-drained soil by rivers in its native habitat in the Sichuan-Hubei region of China. This is one of the few deciduous conifers, thus making it distinctly different from all other Firs, not to mention its gigantic size, and foxy-red flaking bark.

And finally we have Cunninghamii, or Chinese fir, a rare conifer that you would not normally find outside of an arboretum or the garden of a stately home. This genus is clearly named after a Mr Cunningham, and is notable because the shoots and the narrow, slender leaves are all the same pale green, with two bright silvery stripes (yes, those stomatal bands again) on the leaves, both on top and below each leaf, making it very distinctive. These silver-banded leaves spring out untidily all round the shoot, and they are very rigid, making it hard to grasp.

So now that you know that a true Fir's leaves are attached with round green suckers, you can cast an expert eye over every Christmas tree that you see: and in case you were interested, it is easy to tell the difference between Firs (Abies) and Pines (Pinus), because Pine trees have long thin needles, instead of short, flat, leaves.

And if there are numbers of fallen cones beneath the tree, then you know it is not a Fir!

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