To achieve a maximum yield it
is essential to maintain a plant's shape and remove any unnecessary or
damaged growth. This is most important when growing indoors under artificial
Shaping plants (for HID lighting)
When growing under artificial lights (HID or
fluorescent), light is best utilized by
keeping plants short. This can be achieved by pruning and 'training':
Pruning: Once the initial 3 or 4 true
leaves have formed, a plant can be made to possess 2 or more main stems by
removing the 'terminal growing tip' (Fig 13.1a). The new main stems will
grow from the 'axillary buds' located at the remaining leaf nodes (Fig 13.1a
from being shorter than a single stemmed plant of the same age, multiple
stems allow a classic "goblet" shaped structure to form (Fig 13.3a). This
shape generally permits better airflow and light penetration throughout the
Photosynthesis takes place mainly in
young-maturing leaves. Older leaves and those partly shaded photosynthesize
less, thus drawing on the nutrition from young-maturing leaves for their
survival. For this reason, it is worthwhile removing the lower, older
foliage. This practice is most relevant when growing under artificial
lighting because the lower growth is furthest from the light and therefore
has least potential to photosynthesize and be of benefit to the remainder of
For many species, major 'structural' pruning
should only be conducted during the vegetative phase. Unless there is
over-crowding or damaged growth (see below), avoid stressing plants by
pruning during flowering. Plant stress can be minimized by conducting major
pruning in stages. For example, allow plants to rest for a week or so
Training: Upward growth can be
restrained by erecting netting at an appropriate height. Once plants reach
the netting they can either be:
- Trained to grow horizontally (Fig
13.3b). Many plant species will respond to this treatment by producing floral
growth at the point where the stem is bent beneath the net.
- Allowed to grow through the netting
(Fig 13.3a). However, if they grow too tall they can be bent down under the
NOTE: Pruning/ training/ shaping requirements
will vary from one plant species to another. For specific advice ask your
local grow shop or nursery.
Removing dense growth will allow better airflow
and light penetration throughout the foliage. This will enable fruit to
ripen more quickly.
Broken, dying or dead growth is susceptible to
disease and pest attack and therefore should be promptly removed from the
plant and the growing area.
To minimize the threat of pests and diseases,
use the following guidelines when pruning:
to cut: When pruning ensure that the cut is both neat (i.e. no
bark stripped away from the cut face) and close to the stem (Fig 13.4a).
Doing this will help ensure that the cut heals quickly and completely
thereby minimizing the risk of disease and pest attack (Fig 13.4b).
Pruning tools: Suitable tools for
pruning include secateurs or a sharp blade (e.g. scalpel). For a neat and
clean cut, tools should be sharp and sterilized with bleach prior to use.
training/ shaping requirements will vary from one species to another.
For specific advice ask your local grow shop or nursery.
Also, do not
over-prune and risk depriving the plant of leaves that might
be required for a necessary growth spurt.