Willows (Salix spp.) are a wonderful genus. They blur the line between shrub and tree and are understandably overlooked, seemingly becoming more taxonomically complex the more you begin to study them. In Scotland we have approximately 14 native willow species (depending on your biological persuasion). They never grow very tall, the smallest being the dwarf willow (S. herbacea), one of the world’s smallest woody plants at sometimes just a single centimetre high. Despite this, they are probably the most crucial tree at Loch Leven as they can provide vital nesting material, nesting grounds, nursery habitat and food sources for most of our resident waterfowl or passerines as well as bountiful food source for invertebrates – pollinators in particular.
The strip of willow that fringes the water’s edge is known as ‘carr’ and represents a relatively mature stage in the succession of the habitat, where the water-tolerant trees are partly submerged – a bit like a temperate mangrove swamp! Willows are incredibly fast-growing and new shoots can easily put out over a metre of growth in a year. This fecundity can get in the way when trying to manage other lochside habitats like fens or heath, meaning that their removal is often on the menu for our practical volunteer tasks. The quick growth also means that the trunks and branches are not particularly strong and willows are very often the first casualties in high winds, often blocking our paths.
Catkins are something that confuse many (the author included). What are they? They are simply the flowers of the tree, but they are arranged in a cluster, on a spike, with little or no petals. In willows they are pollinated by insects and individual trees have either male or female flowers (dioecious) which look different. Put painfully unscientifically, male willow catkins are yellow and fluffy and female willow catkins are green and spiky. Catkins are some of the first considerable nectar/pollen sources for the year, usually seen between April and May. Our early-season insect transects involve looking up to the canopy to see what bees, butterflies and other pollinators are making use of them.
At Loch Leven we regularly see 3 native willows (along with 2 regularly seen non-native species, 3 rarer species and mysterious records of 2 even rarer species – and that doesn’t include the hybrids or sub-species – so nice and simple then!) Take a look at this blog for a good introduction to some of our trees, willows included. Below is a basic, descriptive list of what willows you can expect to find on the reserve and how to identify them. For similar species, it is usually worth familiarising yourself with at least 3-4 specific characteristics to separate them. Get your cup of tea ready, reading glasses on and notepad out – this lot are not for the faint of heart!
Goat Willow (S. caprea)
- Alternative names: Pussy Willow, Great Sallow
- Sub-species: S. caprea caprea, S. caprea sphacelata
- Similar species: Grey Willow, Eared Willow
- Height: usually 8-10m
- Leaves: Green, 3-12cm long x 2-8cm wide
Goat willow is the most common willow species you’re likely to come across on the reserve but can look incredibly similar to grey willow. It can grow further away from water than grey and usually grows taller. Its leaves are generally also more oval-shaped and the veins on the upper side are a little bit deeper. There are usually no stipules (mini-leaves growing from the base of the leaf stem). The catkins flower earlier than all our other willows here; indeed, it is one of the northern hemisphere’s earliest flowering plants. It can be easily seen all over the reserve, such as between Findatie and Levenmouth.
Grey Willow (S. cinerea)
- Alternative names: Common Sallow
- Sub-species: S. cinerea cinerea, S. cinerea oleifolia
- Similar species: Goat Willow, Eared Willow
- Height: usually 4-15m
- Leaves: Green, 2-9cm long x 1-3cm wide
Grey willow prefers water margins and doesn’t usually grow as tall as goat. The leaves are a little bit smaller, more elongated, less deeply-veined and have stipules at the base of the stems. The bark also grows a bit darker and isn’t as deeply furrowed. It can be easily seen all over the reserve, such as near Kinross Pier.
Eared Willow (S. aurita)
- Similar species: Goat Willow, Grey Willow
- Height: usually 1-2.5m
- Leaves: Pale-green/grey, 2.5-5cm long
Eared willow is the least common of the regularly-seen willows on the reserve and is more distinct. It is a much smaller species, more like a large shrub, and often has browny-red petioles (what joins the leaf to the stem). The leaves are wrinkly at the edges and have sunken veins. It is ‘eared’ because it has regular kidney-shaped stipules growing up the petioles. A good example can be seen in Mary’s Knowe.
White Willow (S. alba)
- Similar species: Common Osier, Purple Willow
- Height: usually 10-30m
- Leaves: Green/pale-green, 5-10cm long x 0.5-1.5cm wide
This is one of two non-native willows, technically an ‘archaeophyte’ (a species introduced in ancient times – usually from around 4500 B.C.-1500 A.D.). It is by far our tallest willow and can be seen shimmering in the wind from far away. Fine hairs on the leaves give its underside an almost white appearance and its bark becomes very furrowed as it ages. It can be seen all around the loch; look out for it near the North Queich bridge.
Common Osier (S. viminalis)
- Alternative names: Basket Willow
- Similar species: White Willow
- Sub-species: Many
- Height: usually 3-10m
- Leaves: Dark-green, 10-25cm long x 0.5-2cm wide
The second of our non-native willows; also an archaeophyte. Its very long, slender leaves allow it to be confused with white willow, but these are noticeably longer and non-serrated (unlike white) on inspection. The leaf surface is also noticeably rougher. It has been used all over Europe for centuries to weave baskets. It grows more on the western side of the loch; you can see it growing at Kirkgate Park.
Bay Willow (S. pentandra)
- Similar species: Tea-leaved Willow, Dark-leaved Willow
- Height: usually 14-18m
- Leaves: Dark-green, 5-12cm long x 2-5cm wide
The first of our rarer willows, it is named for its similarity to the Bay Tree (a kind of Laurel). It grows in wet, boggy areas and has glossy leaves that sport finely-serrated margins (edges) – these look incredibly similar to tea-leaved and dark-leaved willow which are both much less common and not described here. It is visibly an excellent tree for pollinators and has a beautiful scent that lingers for much of the summer season. A good place to see it is at Burleigh Sands.
Purple Willow (S. purpurea)
- Similar species: White Willow
- Height: usually 1-3m
- Leaves: Light-green, 2-8cm long x 0.3-1cm wide
Another rare willow, this smaller species has an introduced and native range so inseparably mixed that the entire population is now classed as native. The leaves can appear almost blue and can be distinguished from white willow by the glabrous (hairless) leaves which are slightly serrated near the tip. One can be seen in the woodland at Findatie.
Creeping Willow (S. repens)
- Similar species: Many
- Sub-species: Many
- Height: usually 0.5-1.5m
- Leaves: Light-green/dark-green/grey, up to 4cm long
The final rarer willow covered here. This short, mat-forming plant is highly polymorphic (can appear very different depending on habitat and location) so is hard to categorize. The underside of the leaves are very silky in appearance and touch. You are unlikely to come across it here without knowing where to look. It can be sporadically seen on our neighbour, RSPB’s, side of the reserve.
Additional to everything just mentioned, many willows will also readily hybridize with each other, further complicating an already complicated taxon, often stumping even expert botanists!
Hopefully this little guide can come in handy if you are looking to improve your Salix knowledge – we see them every day and yet they can be entirely overlooked. There are few places in lowland Scotland better suited to practise than Loch Leven, so spare the willows a minute the next time you find yourself on the reserve!