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After a dry and mild winter, the uninterrupted rain during the
spring pushed the vegetation into an outburst of leaf and flower which, by midsummer,
becomes difficult to sustain as the plants adjust to coping with the sudden lack of water
from the sky.
The size of Stoke Newington streets and gardens helps retain rather than disperse heat.
This factor represents an advantage in winter as it can be exploited to grow exotic
species otherwise too tender, but one which, if underestimated, can turn into a
disadvantage in the summer months, particularly when they become drier.
Evaporation, even on cloudy days, will dry out pots and window boxes every one or two
days, especially where many plants have to share a small space, such as annuals in
containers. This limitation on their root system means that they have to rely completely
on adequate regular watering m order to sustain continuous growth and flowering. One long
weekend away and the plants could dry up or be so weakened that they will struggle to
recover.
Generally, manual irrigation in the garden should aim at fewer but deeper waterings rather
than frequent surface wetting, as the roots will then be able to develop further down into
the soil instead of crowding around the surface (where evaporation is more pronounced)
waiting for their regular small dose. Make sure the soil has not 'caked' into a hard
crust, or the water will just run off and be wasted without reaching the roots.
Hand-held hoses are more accurate than sprinklers, as they allow you to distribute the
water according to individual demands and size. A large shrub will need considerably more
than a small perennial, and its roots will extend outside the outer limit of its canopy.
To help in assessing quantities, try to visualise the size of the underground rootball as
being roughly half the size of its overground growth, and imagine how much water it would
take to soak such an area. If there is no time to water the whole garden this way in one
evening, various sections can be done in rotation. Don't be fooled by light summer rain,
which, unless prolonged, will not reach under dense canopies.
 Learning
to know each plant's needs is also of great importance, as some will require more water
than others, some none at all. Their position, soil and general growing conditions play an
essential role in the correct assessment of their demands. Further, even the timing of
irrigation (never in the sun or heat) can be a determining factor in plant health. Too
much water too late in the summer produces sappy growth which will be much more vulnerable
to frost.
Wisely chosen mulches, also mentioned in the last issue, can help greatly in conserving
soil moisture. This includes some of the more contemporary ones such as cobbles or pebbles
(not gravel, unless you can tolerate its tendency to become a giant litter tray for cats).
Mulches work on the basic principle of shielding the surface from the sun's rays and
reduce evaporation and 'hard baking', which discourages a healthy soil life. The soil
should be wet before application - therefore the best time to apply is usually after
spring rain, or at least following a deep irrigation.
Luisa Ferrari is a garden designer and consultant. She is the London correspondent of
the Italian gardening magazine Giardini and can be contacted on 020 7249 6762
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