Monday, 6 August 2012

Shrubs: the Good, the Bad, the Ugly

The flowering apricot is more of a small tree, but it 
perfectly exemplifies the attractive bare branches of winter,
though here it shows its typical early blossom 
amongst the bare stems.  GOOD

With winter well and truly here, the nature of the deciduous shrub becomes obvious - it loses its leaves and reveals the scaffolding of its branches.  For many species the winter pattern of its branches is a beautiful sight, for although it offers no solid screening as it does in summer, it nonetheless creates a gentle softening of a vista with the tracery of those bare branches.

The Hydrangea has very few dead leaves
caught in its branches.  Its leaves break
down quickly once they have fallen.

Deciduous shrubs do more than reveal their branches, they also show that they have very little build up of flammable material.  The freshly growing leaves are, more often than not, low in volatile oils, contain a high proportion of moisture and come from climates which have cold winters and mild summers.  They are not designed to burn unlike shrubs adapted to water saving such as those from a mediterranean climate.  The dead leaves of the deciduous shrub tend to fall to the ground and, in most cases, will quickly decay over the winter becoming composted and eventually part of the soil.  Thus by summer they pose no hidden fire threat either from the new moist leaves or the old ones becoming part of the top soil.

By contrast an evergreen shrub may build up much dead litter caught in the branches, that cannot readily be seen, because of masking by the evergreen leaves.

A Book Leaf Cypress looks green on the outside, but part
the leaves and there is dry and inflammable litter inside.

Euonymous japonica

Of course, there is great variation and a spindle berry, Euonymous japonica, is quite low in flammability, although an evergreen.  Its leaves are quite large, fleshy and moist without volatile oils.  When looking into the shrub there is very little in the way of leaf litter caught in the branches.

To sum up, choosing deciduous shrubs are often a safer choice for fire-prone areas, partly because they come from cool temperate areas and are not inherently inflammable, but also because it is easy to see if there is a build up of inflammable material.

If you do choose evergreen shrubs, choose ones like the Euonymous with broad, fleshy leaves.

If you really like plants such as diosma or artemisia keep them small and low to the ground - less than a metre - this regular cutting back will reduce the litter build up.
Artemisia, Wormwood, is best cut back regularly, but it does
have volatile oils and needs controlling.
A qualified GOOD.  High maintenance!