Tree of the Week

Week 8 - Flowering  Cherries (Prunus spp.)

A departure for Tree of the Week this week, with almost a whole genus rather than a single species of tree. I’m just being indecisive because on the streets near you right now, looking ridiculously cheerful, are so many flowering cherries of various kinds it is not realistic to choose just one. There are many varieties and they have been on our shores since the early twentieth century, with the exceptions of two natives; the bird cherry – Prunus padus, and Prunus avium, the wild cherry. Prunus avium is more common in the south of England and Prunus padus, preferring wetter and more acidic soils, in the north. They aren’t keen on cold winds and the blossom only looks amazing for a few short weeks, but you have to admit that for that time they really do the business.  Most also have great Autumn colour, in yellows and bright reds, so this isn’t the only season of interest. It can be hard to tell one from another. Almond and blackthorn blossom are both similar (both also Prunus), but you won’t mix these up as cherries always have those oval or linear horizontal markings on the bark of the trunk, which are the lenticels through which gas exchange occurs between the plant’s tissues and the atmosphere, see examples below.

Prunus padus

Prunus avium

Tree of the Week

Week 7 – Crataegus monogyna; Hawthorn

Hawthorn may not be a big impressive tree but at this time of year it is exciting because it is one of the first to come in to leaf. Just as it seems like winter will never end, you spot an unfurling hawthorn leaf and – hurray! Spring has truly arrived. The form of the plant could really be anything, depending on context – from the clear stemmed specimens in open parkland at Tatton to a formally clipped garden hedge and all kinds of wild hedgerow in between. Identify it, then, from its many-lobed bright green leaves un-concertina-ing now, and thorns about 10mm long. In May there’s the uplifting blossom (may blossom) and in late summer deep red ‘berries’ (haws) dangling in small clusters from the twig. Small birds seem to love it, and it will grow in just about any soil apart from very wet.

                   

  

Tree of the Week

Week 6 - Salix caprea; Goat Willow, Pussy Willow

Right now Salix caprea is doing its party trick – fluffy yellow catkins are bursting out from pale-grey  velvety cases all over the branches. This is a small, hardy, native tree and another pioneer species; likely to be growing in damp areas and scrubby neglected ground. When it colonises pond and wetland margins it gradually dries the soil and consolidates the ground with its root system, so think about where you put it/remove it from, as it will have a big effect on the nature of the habitat. The twigs are still leafless at the moment, but just so you know, here is what to look for in late spring – its easy to think of a typical willow leaf as a long thin pointed oval, pale green and quite soft, but beware – this willow has a rounded darker green leaf which is quite tough and nothing like the weeping willow leaf.

For more details about Salix caprea, have a look at the RHSwebsite.

Tree of the Week

Week 5 -  Alnus glutinosa; Alder

Alder is interesting in March because you can see the new male and female catkins held on the twigs alongside last year’s dried seed cases. These look a bit like pine cones and at this time of year are still clinging on to the tree in abundance. They are large enough to see clearly from the ground if you look up in to the canopy. The male catkins right now are about 4cm long and quite bright green and yellow because they are nearly ripe, though they’ll mostly be too high up to appreciate this. So, as long as you don’t confuse these catkins with Hazel (you won’t, this is a much bigger tree) or the seed cases with Plane (you won’t, these are smaller and oval not round) this is an easy one to spot! In summer the leaves are distinctive because they have a blunt or inward-curving end, rather than a common pointy-ended leaf shape, see below.

Alder is our most common waterside tree, a lover of all damp soils and a pioneer species. Their roots fix nitrogen in the soil, so when Alder woods are cleared the resulting ground is very fertile. They also help protect stream banks from erosion.

What urban vegetation is for...number 8; It has concord with the identity of the place and is located in its biotic context

In this there is an important difference between architects and landscape architects. An architect might think of ‘place’ as something you create, design, build, build up. An LA, however, is more inclined to see a place as a pre-existing entity; somewhere with its own set of characteristics such as a microclimate, possibly a set of native species and hopefully a soil of some specific kind. It might have ancient road patterns, field boundaries, or geological quirks. To us, a place already has a spirit. These aspects of a place can’t really be fundamentally altered, even if we wanted to do so. So, when we design and when we build, we build across, but not with the aim of painting something new as if from a blank canvas – instead we aim to enhance, renew, enrich, regenerate. Landscape Urbanism takes this basis for our professional approach a step further, by embracing the aspects of a site that would previously have appeared to be its most intractable problems.

There are different ways in which designed vegetation structures can concord with the identity of a place. Of course you can use only species native to the spot, if that is what you want. Certainly this is the best way of ensuring plant survival and future health. On some sites, though, disturbance of soil structure and vegetation is so extreme that to try to design a way back through time to its pre-existing ‘natural’ state would be impossible and also pointless. Our job here is to piece together a reformed identity from the shreds of the old. What can guide us in this? For a start there are the pragmatic demands of the site; for remediation, shelter, flood alleviation, microclimate amelioration, energy or food production. All of these can be addressed in whole or part through vegetation.  Other prompts for the designer might come from more symbolic historical or cultural cues such as derelict structures or adjacent industry. Existing and past communities of people and animals can have their influence too, not just on gestures such as pieces of public art, but on fundamental vegetation structures – on new natures.

Tree of the Week

Week 5 - Corylus avellana; Hazel, Filbert

For the last couple of weeks Hazels (in Manchester) have been looking great because of the catkins, which are the best route to identification at this time. Like the example below, the trees are hung all over with these golden pollen-bearing catkins of about 5cm in length, held in groups of up to six or so. They look wonderful lit up by low winter sunshine. The hazel is usually more shrub than tree, especially coppiced specimens, which will be evident because of the many slim stems coming straight up from ground level. In summer the leaves are rounded in shape with toothed edges and a pointy end, and the nuts are usually held in clusters of 2 or 3. Don't count on seeing these, though, as urban squirrels usually take the female flowers or the developed nuts. Coppicing hazels to produce many stems of new wood for fencing materials or fuel wood is an ancient practice, recently attracting attention due to hazel's possible potential as a biofuel. It is an understory species in woodland and common in hedgerows.
There are good red/purple forms like Corylus avellana 'Zellernus', bottom right.