At the time of writing, the end of October, the shade
temperature is still about 28 centigrade. I could be forgiven for
thinking that winter is ages away, but in gardening terms, this could
be a costly mistake, despite living in a relatively mild winter
climate. I live, work and garden in central Israel. In some areas the
winter lows reach about -2 c. in others, frosts are very rare. If like
me, you live in a dry Mediterranean climate, typified by mild wet
winters, then it would be prudent to be aware of the effects that
pruning at this time of year can have on the garden plants, and
particularly on the most precious object in the garden - the tree.
Before
going into that though, let's discuss briefly some reasons for pruning
in or around the autumn. The fall is actually a mini growth season in
Mediterranean climates. With the drop in temperatures, rise in
humidity, and shorter days, plants tend to enjoy a brief period of
resurgent growth after the torrid heat of the summer. It can be
worthwhile taking advantage of this, to encourage compact growth in
landscape bushes, which can be effected by light pruning and clipping.
The same is true of many herbaceous flowering perennials, whose flowers
have withered, and look somewhat lank and "leggy". Some ornamental
grasses tend to look extremely poor as winter approaches, while pruning
them down, encourages new growth before the low temperatures curtail
further growth until the spring.
There is no problem in pruning
cold hardy plants in the winter, but cold sensitive species are liable
to be damaged, sometimes fatally so, by being cut during the cold
season, or in proximity to it. To be safe, cold sensitive plants should
not be touched from about six to eight weeks before the
possibility of frost or chilly temperatures. The reason is that wounds
to non-hardy plants caused by pruning cuts, are highly likely to be the
source of bacterial or fungal infection, and to increase the plants'
susceptibility to the cold. So if your still basking in the glow of the
autumn sun - BEWARE!
When it comes to naturally deciduous plants,
which are generally cold hardy in any case, light pruning is fine,
although the heavy seasonal tree pruning, or the pruning of rose bushes
and Crape Myrtles, should be carried out during the dormant season. In
mild winter climates, it's important to delay this type of pruning
until the later half of the dormant season, and not in the middle of
the winter as in continental Europe or North America. This will be the
subject of a future article.
So how are you to know which plants
are liable to be cold sensitive, and which ones are hardy? Obviously it
helps to know the precise botanical names of your garden plants, and to
check up their hardiness in literature or on the net. Here are some
general guidelines though which you may find useful.
*
Evergreens, excluding coniferous plants, vary in their sensitivity, but
are never hardy to temperatures below say -6 or -7c.Examples like Olive
trees, Carob and various species of Lantana come to mind. When in
doubt, assume that an evergreen specimen is sensitive and do not prune until every possibility of frost has passed in the following spring.
*
Plants that drop their leaves in the winter, may not be naturally
deciduous, but may in fact be of tropical or sub-tropical origin, and
the leaf drop occurs in reaction to the relative cold to which the
plant is exposed to during the winter. Here lies a potentially nasty
trap, because species in this category, like Duranta or Lantana for
instance, can be highly marginal for your area in the best of
circumstances. These types must never be touched until the spring. On
the other hand, and this where things can get a bit complicated, the
worst time to heavily prune the real deciduous plants is during the
spring, as the sap rises through the wood after the winter dormancy has
elapsed. So before rushing in to prune bare leaved trees and shrubs,
find out exactly what you are pruning!
I've
been gardening in a professional capacity since 1984. I am the former
head gardener of the Jerusalem Botanical Garden, but now concentrate on
building gardens for private home owners. I also teach horticulture to
students on training courses. I'd love to share my knowledge and
experience with you.