Plane simple - how to tell a sycamore, a Norway maple and a London plane apart

We have three trees in the UK that look superficially very similar. They are

• Acer pseudoplatanus - the sycamore
• Acer platanoides - the Norway maple
• Platanus x hispanica (a.k.a. Platanus x acerifolia) - the London plane

All three trees have pretty wide, palmate (in the shape of a hand) leaves with more or less pointy tips, and they all grow to roughly a similar height. For this reason, they can sometimes be hard to tell apart. I'm gently reminding my children of the differences each time we pass one, but often my four-year-old daughter will point to a London plane and declare that it's a sycamore!

Are they really that similar?

Now I should say that I have seen a fair few people pronounce adamantly that these three trees cannot be confused with each other, particularly the London plane with the others. And, indeed, when you know what to look for, it's easy to tell the plane apart.

But the fact that the trees are easily confused is testified to in both their common and their taxonomic names.

A Platanus x hispanica (London plane) in London

Let's start with the London plane. The taxonomic name Platanus comes from the Ancient Greek word πλάτανος (plátanos). This referred to what taxonomists now call Platanus orientalis (the "Oriental plane"). The leaves of this tree are very distinct and cannot be confused with the London plane or either of the two Acer trees described above.

Platanus x hispanica is actually a hybrid of Platanus orientalis and a tree from North America - Platanus occidentalis (the "Western plane" or "American sycamore"). It's not known quite where the two pure species hybridised to create the London plane. The word "hispanica" in the taxonomic name derives from the commonly-held belief that the tree originated in Spain, but it's not certain that this was the case.

The newer name "acerifolia" means "maple leaf" and is evidence of the perceived similarity between the leaves of the London plane and those of (at least certain) maples. Platanus x acerifolia is now the more accepted name in the taxonomic community, but, for historic reasons, P. x hispanica still persists, and is more prevalent, in the UK.

Acer pseudoplatanus is what we call the sycamore in the UK. Again, the name points towards the potential confusion with the other trees: "pseudoplatanus" means "false plane". In the US, they look at it the other way round. Americans commonly refer to plane trees as "sycamores" and to A. pseudoplatanus as the "sycamore maple". (In fact, originally, the word "sycamore" referred to a completely different plant - Ficus sycomorus (the "sycamore fig"), a plant which doesn't even grow in the UK or the US!)

The similarity between the leaves of the P. x hispanica and A. pseudoplatanus is actually quite apparent. In this respect, Acer platanoides - the Norway maple - is perhaps the outsider, but even then the similarities are reflected in the name. "Platanoides" literally means "shaped like a plane".

Despite being close in look, the three species are not cousins. Planes and maples are only very distantly related, and it's possible to see this when examining them a bit more closely.

Let's start by working out how to tell a plane apart from a maple. Then we'll look at how to work out whether that tree is a sycamore or a Norway maple.

Planes vs maples

Leaves

Leaves are always the first thing we notice on trees, so let's take a closer look.

The quickest and easiest way to tell a London plane apart from a sycamore or a Norway maple is to examine the leaf veins. These are the light green lines that run along the inside of the leaf. Take a good look at the sycamore and Norway maple leaves below. You'll see that, on both leaves, the main leaf veins - the heavier lines - all begin at the base of the leaf where it connects to the leaf stem (the "petiole"). The veins all radiate out from the one point. This is a universal feature of maples (Acer species).

Acer pseudoplatanus (L) and Acer platanoides (R)
Acer species leaf veins always radiate out from the leaf base

Now look at the London plane leaf. Yes, the overall shape is quite similar to a sycamore, less so to a Norway maple. But the leaf veins do not all start at the base. Rather, the central leaf vein emanates from the base, like a continuation of the petiole. Then there are two diagonal leaf veins and two horizontal leaf veins that strike out to the side points of the leaf. But they both branch out from the central vein, not from the base of the leaf. Again, this is a universal feature of planes (Platanus species).

Platanus x hispanica (x acerifolia)
Platanus species have a central vein from which all other veins branch out

So there you go. That's how to tell a London plane (or, indeed, any plane) from any kind of maple. Now it's not always quite that easy to tell the difference. Sometimes, particularly on younger London plane leaves, the diagonal and horizontal veins begin so close to the beginning of the central vein that it looks like they radiate from the leaf base. But if you look very carefully, you'll see that's never the case.

However, in case you're still not sure, there are a few other ways to tell a plane from a maple.

Fruit

There is no mistaking a plane fruit for a maple fruit.

All Acer species have distinctive fruits called "samaras". These are made up of a pair of papery wings, each of which contains a seed - so the entire fruit contains two seeds. These are sometimes referred to as "keys" and, in the UK, very commonly known as "helicopters" after the rotating action they exhibit when they fall to the ground.

A clutch of Acer platanoides samaras

Plane fruits, by contrast, are spiky balls that hang down from the branch, superficially resembling a horse chestnut (Aesculus hippocastanum) or sweet chestnut (Castanea sativa) fruit. Actually, the ball isn't a single fruit, but rather a collection of several hundred tiny, dry fruits called "achenes". Unlike a maple, whose fruits form between May and July, a London plane takes up to six months to form its fruits, which cling onto the tree well through Autumn and often deep into Winter.

By Roger Culos - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=38828451

Platanus x hispanica fruit

Of course, this most differentiating feature of planes and maples won't help you if the tree you're looking at hasn't been pollinated yet.  So, there is one more thing you can look at.

Leaf arrangement

Planes have alternating leaves. In other words, you'll find a sole leaf branching out from one side of a stem, then another leaf a little further down branching out in the opposite direction, then another leaf branching out in the same direction as the first, and so on. You will never find two leaves branching off at the same point in different directions.

Platanus x hispanica showing alternating leaves

Maples, however, have opposite leaves. As simple as it sounds, this means that the leaves branch off from the main stem in opposite pairs. So, if you find that the leaves sit in happy little couples all the way down the branch, you're definitely not looking at a London plane.

Acer pseudoplatanus showing opposite leaf pairs

So there you have it. Three sure-fire ways to know whether you're looking at a Platanus x hispanica (London plane) or a maple (Acer). What's a lot trickier is to work out whether your tree is a sycamore (Acer pseudoplatanus) or a Norway maple (Acer platanoides).

Sycamore vs Norway maple

Generally, we can examine the same features, but in a little more detail, to decide whether we're looking at a sycamore or a Norway maple. However, one thing does need to be said right from the start: these two trees do look very similar. I'm going to show you some examples below that exaggerate the features of the two species. In reality, both species exhibit a large amount of variation, and it's quite easy to find leaves that could be either-or.

Leaf tips and lobes

The most commonly cited difference between a sycamore and a Norway maple is the tips of the leaves. The "tips" of a leaf represent the point where the veins reach the leaf edge. Take a look below at the pseudoplatanus leaf on the left and the platanoides leaf on the right.

A. platanoides leaves typically have finer, more pointed tips than A. pseudoplatanus leaves

The tips of a sycamore are usually fairly blunt. There is a point, but it's short and unremarkable and quickly broadens out into the thick lobe of the leaf. The tips of the Norway maple, however, are more pronounced and taper to a point. Often, as in the splendid example above, there are multiple tips at the end of a lobe on a Norway maple leaf, giving a "spiky", more traditional "maple-like" appearance.

Alongside this, notice how the lobes (the bulges in the leaf) on a sycamore are cruder and blockier. Shaped like eggs, it's as if someone took three separate leaves and glued them together. The lobes on the Norway maple, however, are slenderer and the grooves between them cut deeper, giving the lobes the appearance of tongues.

As I say, though, it's very important not to lay too much emphasis on these points. The leaves displayed above are exemplar specimens. In nature, variation occurs on a massive scale. Take a look at the leaf below.

This doesn't have the multiple tips of the Norway leaf above. The lobes are much blunter and there is very little in the way of a deep groove between the two main side lobes. But this is also a Norway maple (Acer platanoides) leaf. Even though they're less pronounced, you can see the tapering points at the ends of the tips, and the central lobe is still quite slender, with sides that gently taper inwards towards the centre of the leaf.

Now how about this one?

This also has a central lobe that tapers gently inwards. The lobe is also quite long, with fairly deep grooves separating it from the sides of the leaf. You can also see that the bottom two lobes, at the base of the leaf, are quite distinct, as in our Norway maple leaves above. And the tips are not so blunt, particularly on the right-hand side of the photograph. But this is a sycamore (Acer pseudoplatanus) leaf. Despite having more pronounced tips and deeper grooves, the lobes are still chunky and lack the delicate feel of a Norway maple.

So, are there any other ways we can tell the two species apart just by looking at the leaf?

Leaf edges

Another way to quickly distinguish between a sycamore and a Norway maple is by looking at the edge of the leaf. Sycamore leaves generally have a "serrated" (or sometimes "doubly serrate") edge, meaning the leaf edge has small, pointed protrusions that make it look like a saw. Norway maple leaves, by contrast, generally have an "entire", or smooth, edge.

Acer pseudoplatanus (L) has serrated edges, whereas Acer platanoides (R) has smooth edges

Yes, there are points on the Norway leaf, but these are much farther apart from each other - indeed, on some varieties, there may be no points between those formed by the main veins. These leaf edge between the points is not serrated.

Leaf veins

Leaf veins and lobes are inextricably linked. The direction and extent of the veins inform the size, shape and number of lobes. You'll generally find it said that both sycamores and Norway maples have "five-lobed leaves". This means that there are five main leaf veins that form five main parts of the leaf. These normally include a central lobe formed from the central vein, two big side lobes formed from the two diagonal veins, and two smaller lobes towards the base, formed from the two horizontal veins. Five veins, five lobes.

For sycamores, this is absolutely true. Let's take another look at those two sycamore leaves I showed you.

Acer pseudoplatanus leaves have five veins radiating from the leaf base

Very clearly five veins emanating from the leaf base, and so it has five lobes. Even though the basal lobes in the leaf on the left are small and (particularly on the left side) a little indistinct, they are very certainly there.

Now let's count the veins and lobes on a Norway maple leaf.

Acer platanoides leaves have seven veins radiating from the leaf base

The leaf clearly has seven veins emanating from the leaf base. In the exemplar leaf on the left-hand side, this has given rise to seven very distinct and beautiful lobes. In the leaf on the right-hand side, the top three lobes (3, 4, 5) are clearly visible and the middle lobes (2, 6) discernible. The basal lobes (1, 7) are really only just there. In fact, the left-hand basal lobe (1) is almost non-existent.

This is why you may see books or websites saying that Norway maple leaves have between five and seven lobes. The two basal lobes may or may not be developed or prominent enough to be considered lobes in their own right. Indeed, younger Norway maple leaves may not have all seven veins yet, or the basal veins may be very faint indeed. But, without fail, if it has seven veins radiating from the base, it's a Norway maple.

If you're still not sure, take a look at the back of the leaves.

Our sycamore leaf - with its five veins - is in the top left. Our perfect Norway maple leaf, with seven distinct veins - is in the top right. And at the bottom is our more dubious leaf, with seven veins radiating from the leaf base, indicating that it too is a Norway maple.

OK, I know. Those lower veins on the third leaf really are quite faint. And, as I say, in some leaves they may not appear at all. Plus, there are lots of veins on a maple leaf besides the five or seven main ones. What if you're mistaking one of the secondary veins for a primary vein? Well, there are two other quick ways to tell a Norway maple and a sycamore apart.

Fruit

As I mentioned above, all maples produce fruit called "samaras" - fruits with wings. Actually, the fruits are "double samaras", as they're made up of a pair of paper wings. Each wing encloses a seed at its base. When the samara falls from the tree, it twirls quickly round and round like a rotor, earning it the colloquial name "helicopter".

Sycamore samaras and Norway maple samaras are subtly different.

The wings on the samara of a Norway maple are spread far apart, almost to the point of being a straight line, like a gymnast doing the splits. And the seeds inside the samara are flat and disc-shaped, as if they've been run over by a steamroller. In fact, it's this flat seed shape that characterises the section Platanoidea, to which the Norway maple and its brother, the field maple (Acer campestre), belong.

An Acer platanoides (Norway maple) samara and a similar (but smaller) Acer campestre (field maple) samara, both with widely-spread wings and flat seeds

By contrast, the wings on a sycamore samara are angled downwards. Sometimes the angle is so sharp the two wings almost touch or overlap; at others, the gap between them is clear. But, in either case, the wings do not stretch out to the sides. And, in contrast to the Norway maple, the seeds of a sycamore are ridged and bulbous, forming a distinct, darker top to the samara.

Two Acer pseudoplatanus samara, from different trees, showing wings angled downwards

Sycamores and Norway maples generally flower and fruit at around the same time, so it should be eminently possible to compare their samaras.

Sap

As noted above, the Norway maple, along with its brother, the field maple (A. campestre), belongs to a "section" of the Acer genus called "Platanoidea". One of the characteristics of the Platanoidea is that they have a milky sap running through their shoots and leaves. You can see this sap by ripping a Norway maple leaf in half horizontally. (I would suggest ripping close towards the base, as that is where the sap-carrying veins are widest.) After being ripped, the torn leaf will ooze an opaque white liquid. Sycamores do not contain this milky sap, so this is a another useful way to tell them apart.

The milky sap from an Acer platanoides leaf

Other supposed distinguishing characteristics

Personally, I think the differences highlighted above are really the only reliable ways to tell a sycamore from a Norway maple. Nevertheless, I feel obliged to mention a few more differences that are touted from time to time.

• Bark.  I have heard it said that you can tell a sycamore from a Norway maple by its bark. Norway maple bark is said to be dark brown with clear vertical ridges, whereas sycamore bark is light grey and scaly smooth. And I must say that many of the trees I have come across accord with these descriptions. But I have equally seen Norway maples with smooth bark and the odd sycamore with a more furrowed trunk. I even have a Norway maple in my own garden with a very smooth, light grey trunk - so much so that, when I first started out, I thought it a sycamore. A lot of the trunk's appearance depends on the age of the tree and the conditions it has had to endure, and so I wouldn't rely on this for an ID.

Acer pseudoplatanus trunk (L) and Acer platanoides trunk (R), but they don't always look like this

• Petioles.  I read once somewhere that, supposedly, sycamore leaves are carried by red petioles (the little stalk between the branch and the leaf) and Norway maples by green petioles, and that this tells them apart. I'm afraid that is nonsense. Yes: I have seen more sycamores with red petioles and more Norway maples with green. But it's perfectly possible to see examples the other way round. Take another look at the less perfect Norway maple leaf further above. It clearly has a red petiole. And beautiful "red" versions of the Norway maple, such as Acer platanoides f. schwedleri, always have red petioles. So don't go off petiole colour.

• Tar spot.  Tar spot is a leaf disease caused by the fungus Rhytisma acerinum. "Rhytisma" comes from the Greek word for "patch", and "acerinum" is a pseudo-Latin word making the connection with maples. The fungus initiates chlorosis in the tree, causing the leaves to produce less chlorophyll. This results in black spots with a yellow border, which appear all over the leaf. It typically occurs in late Summer and early Autumn and does no lasting harm to the tree. Tar spot more commonly affects Acer pseudoplatanus, but it can affect Acer platanoides too, and so is not a way to tell the two species apart.

CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=333687

Tar spot on an Acer pseudoplatanus leaf

So there you go. Now you are equipped with the knowledge to tell a London plane from a sycamore from a Norway maple.