Tree of the month: Sallow sees in the New Year

YOUR average punter doesn’t sense spring until late March and the vernal equinox. However, for me, spring starts on New Year’s Day, the first day of January, named after Janus, the Roman God of doorways and gateways, who faces both ways to see back into the past and forward into the future. 

It’s only 10 days since the shortest day of the year, but the landscape seems so much brighter and cleaner. And on this first day of January, sun rain or snow, the first sign of spring in flowering native sallow is there for all to see. Male catkins suddenly appear as silvery, silky tufts of ‘cat’s fur’ before the yellow, pollen-packed anthers on stamens are revealed in February and March. Feel the catkins in early January and you will sense why sallow is called ‘pussy willow’.

NO WIND IN THESE WILLOWS

Ever wondered why male flowers of Salix caprea (great sallow) and Salix cinerea (grey sallow), our two main native sallow species*, are prostrate, soft and scented, in contrast to the pendulous, wind-pollinated male catkins borne by other members of the plant family Salicaceae (willows and poplars)? 

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Sallow embarked on an alternative evolutionary pathway, opting for insect pollination, despite the earliest of seasonal starts. Sallow teases with a glimpse of male flowers in January before bursting into bloom in late February and early March. It bribes insects with the first honeypot of the year – not an easy task, since few insect pollinators are on the wing. 

On a bright and sunny but still cold early-spring day, the canopy looks like a yellow cloud in a clear blue sky. Closer viewing reveals swarms of winged insects drinking nectar and gathering pollen from the mass of yellow-tinted flowers on male sallow trees. Sallow provides a first feeding for still groggy insects waking up in late winter. Nectar is produced by male and female flowers on separate trees of the dioecious sallow.

An initial literature search for insects drinking nectar from Salix caprea and Salix cinerea was unsuccessful. More fruitful were searches of North American literature relating to that continent’s native Salix discolor, also called pussy willow, closely related to our native sallow. A wide spectrum of insects are documented as pollinators of American pussy willow – mainly mining bees and syrphid flies (hoverflies), but also honey bees, blowflies and a range of beetles. 

The appearance of male flowers as soft, silky, furry catkins as early as January is why great sallow is called ‘pussy willow’ (evergreen English yew in the background).

A more exhaustive UK search found exactly what I was looking for – a first han account of insects visiting sallow catkins in full flower, as early as late February but usually in March, in Norfolk, East Anglia. The list includes flies, honey bees, mining bees (Andrena bicolor) and bumble bees, especially the early bumble bee (Bombus pratorum) which, as the name suggests, emerges earlier than other Bombus species to start the colony cycle as soon as February. Male catkins make more pollen and therefore attract more insects, but the less-showy female catkins attract insects which may have visited male catkins and picked up pollen. Early flying butterflies including peacock, red admiral, brimstone and comma were recorded on sallow. 

Sallow is a boon to birds as well as bees. Summer migrants including whitethroats and warblers may already have arrived to find few insects on the landscape, but flowering sallow provides a focus for what flying food there is. Wind comes into play when pollination is done and dusted to produce spectacular sights when sallow grows near water. Male trees drop their spent flowers into the wind to form attractive patterns on the water.

POPULAR WITH THE PEOPLE

Great sallow is probably the better known of the two native sallow species. It produces a larger and longer-lived tree, bearing bigger and broader leaves, and it is not so dependent on open water and marshy land. And its pussy willow catkins are whiter than the silvery counterparts of grey sallow. 

Grey sallow is found at the margins of small ponds, in ditches and dykes and on marshland, but great sallow appears to display a more catholic taste in soil and its saturation. Stems of great and grey sallow were widely used to celebrate Palm Sunday, which became known as Pussy Willow Sunday, nowhere more so than Lancashire, with sallow used as a substitute for palms which would have struggled to survive as far north as Preston. 

According to an article in The Lancashire Telegraph (‘Don’t weep for lovely willow’ by Ron Freethy, 5 January, 2009), there is another common name for sallow, with Lancashire children calling it Sallon after the village of Sawley (near Clitheroe in the Ribble Valley), once called Salley and apparently still famous for its willows. Pussy willow is increasingly popular with florists for arrangements and as a stand-alone winter-season decoration in the home.

Male grey sallow in full bloom, well at home in a ditch on wet common land in spring of 2006.

The alternative common name for Salix caprea is goat willow. The first known illustration of great sallow appears in Hieronymus Bock’s Herbal (1546) and depicts sallow being browsed by a goat. ‘Caprea’ means ‘wild she-goat’ in Latin –appropriate, since Salix caprea was widely used as fodder for goats.

TREASURED TREE, FOREST WEED AND UTILITY TIMBER

Sallow may well be popular with the people, but it has never impressed foresters, who regard it as a shrubby weed. Iconic forestry texts cover other native willows – osier with its ‘witheys’ used for classical basket-making, white or crack willow for Sussex trug basketry, cricket-bat willow for sporting accessories of the same name, and sawn willow timber for the blades of steam-boat wheels and the shrouds on watermill wheels – but offer essentially nothing about sallow.

That no substantial use was found for sallow, which according to Oliver Rackham formed the first wildwoods in Britain (along with birch and aspen) after the last ice age, is strange to say the least.

Sallow doesn’t even feature as firewood, despite there being a lot to burn. Woodsmen who know about these things describe sallow as a very wet wood that doesn’t dry properly in the round and requires splitting. It is a brittle wood which crackles and spits when burned and is more suitable for stoves and boilers than open-hearth fires.

But every dog has its day and that’s coming quickly for sallow as a utility timber, standing or sawn, due to a range of contemporary problems, including alien tree diseases and increased flooding, coupled with lack of forest cover on hillsides and obsessive building on flood plains, against all sound advice. 

Early-flying red admiral butterflies are just one of the species that visit sallow catkins to drink the nectar.

I recently visited an Oxfordshire woodland planted 18 years ago with a substantial common ash component (before Chalara ash dieback disease appeared in 2012). Grey sallow started to invade soon after planting and is now established as sizeable trees. In normal circumstances, this would have downgraded the woodland, but it is something of a saviour because the ash trees are currently dying big time. It is clearly too late to step in and beat up with other species, but there is no need, because grey sallow is plugging the gap.

Sallow is used in the construction of living dams and flood defences along waterways at increasing risk of flooding. The Eurasian beaver coming home to its old haunts after anything up to 1,000 years must be relieved to find sallow, a favoured tree species for felling and dam building, still in abundance after all this time. 

A propensity to coppice is advantageous in water-related repair situations. Oliver Rackham gives great and grey sallow five-star ratings for their coppicing capability. There is a small but sustainable market for sallow planting material. A nurseryman I know gets the most enquiries for great sallow, which he sells to the tune of 2,500 trees per year.

THE GREAT COMEBACK

I always knew where to look for the first signs of pussy willow, on huge veteran great sallow trees along a railway embankment at Potters Bar in Hertfordshire. These valuable veteran trees with 70–100 years on the clock had stood by while LNER Class A4 steam locomotives (including the Mallard), Delta diesel locos and Intercity 125 trains had hurtled through Hertfordshire on their way to Scotland. 

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The trees escaped felling after the fatal train crash at Potters Bar station on 10 May 2002, but finally succumbed when National Rail began felling woodland wholesale in 2018. These veteran sallow trees were nowhere near the track and not posing a threat, but contractors tried to erase them completely by peppering the stumps with plastic plugs containing herbicide. Sallow failed to oblige and the resulting regrowth, now two metres high, should bear pussy willow this year.