Agriculture Reference
In-Depth Information
2
1
(a)
Figure 1.7
Corylus avellana 'Red Majestic' (Corkscrew
hazel) with insert showing detail of the contorted
twigs
growth, which include nutrient deficiencies or
imbalance (see Chapter 14). Damage may also be
attributable to environmental conditions. These
disorders are examined in Chapter 19 along with the
problem of plant diseases, the symptoms of which
may look similar. The problems that plant pests bring
and how to deal with them is the theme of Chapter 18.
The incorrect functioning of any one factor may result
in undesired plant performance. Factors such as the
soil conditions, which affect the underground parts of
the plant, are just as important as those such as light,
which affect the aerial parts. The nature of soil is dealt
with in Chapter 12. Increasingly plants are grown in
alternatives to soil such as peat, bark, inert materials
and water culture, which are reviewed in Chapter 15.
(b)
Figure 1.6
a) healthy white roots b) poor roots in
waterlogged pot
It is important to have a clear idea of what a
healthy plant
is like at all stages of its life. The
appearance of abnormalities can then be identified
at the earliest opportunity and appropriate action
taken. This is straightforward for most plants, but
it is rather important to be aware of those plants
whose healthy leaves are not normally green, that
is, variegated, yellow, silver, purple and so on (see
p. 114). Many 'stunted' plants are, often expensive,
dwarf forms such as
Betula nana
,
Berberis thunbergeii
'Atropurpurea Nana'. Some appear 'monstrous' -
for example, those with contorted stems such as
Salix babylonica
var.
pekinensis
'Tortuosa' and the
corkscrew hazel
Corylus avellana
'Red Majestic'
(see
Figure 1.7).
It should be noted that
physiological disorders
account for many of the symptoms of unhealthy
Ecology and gardening
As well as understanding how individual plants
operate and having a knowledge of their requirements,
it is important for gardeners to appreciate how they
relate to their surroundings and the organisms that
live there, whether this is other plants, the animals
that live with them and on them, or the non-living
parts of their environment. The subject of ecology
