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Ventilation should be applied
freely during warm weather and moderately during cooler periods.
The free circulation of air amongst plants helps to reduce the
incidence of common fungal diseases like botrytis.
During the duller days of winter
and early spring ensure that maximum light is admitted to the
greenhouse. Clean the glass in the fall and then again during
early spring. Cleanliness is important in all parts of the structure
if pests and diseases are to be successfully controlled. The
thorough cleaning of the rafters, brickwork and other fixtures
during the winter with a strong garden disinfectant will pay
dividends.
Dead leaves and discarded plants
should be disposed of regularly and should not be allowed to
accumulate beneath the staging where they will harbor pests and
diseases. Regular cleaning and maintenance results in healthy
plants and a trouble-free structure in which to produce them.
One of the on-going activities
in a well managed greenhouse is re-potting. This applies to all
permanent plants and those that are growing on and need periodic
removal to a larger pot size. Some flowering plants like pot
chrysanthemums and primulas are completely exhausted after flowering
and are best discarded rather than re-potted. They rarely regain
their former glory.
Re-potting often causes some
consternation, particularly to new gardeners, for there is believed
to be a certain mystique surrounding the operation and an uncertainty
as to when to perform it. It is obviously better to re-pot a
plant just before it needs it, but the beginner may have difficulty
in recognizing just when that is, so plants are often allowed
to go beyond that point and start to deteriorate.
Paleness of foliage and gaunt
appearance is the overall aspect of a plant that is in need of
re-potting. The pot-ball will be hard and congested, often with
roots pushing out through the drainage holes of the pot. The
compost surface will also probably have a stale look about it
heightened by the presence of mosses or liverworts.
When re-potted, pot-bound plants
rapidly recover from their ordeal, but it is better to catch
them before they go into decline so that strong healthy growth
can continue unchecked. During the active growing period do not
be frightened to turn a plant out of its pot and inspect the
root-ball. There is no need to pull it about, but a regular inspection
will indicate whether everything is in good order.
Do not pay too much regard to
the concentrated presence of roots towards the sides of the pot,
for it is quite natural for them to gravitate there. It is not
necessarily an indication that the plant must be re-potted. Similarly
roots that push through the drainage holes may not always indicate
congestion within the pot, for if the pot has been stood on a
gravel tray in moist conditions it is quite normal for roots
to probe around outside.
The best way to tell whether
a plant needs re-potting is to pinch the root-ball with your
fingers. If there is any flexibility in the compost it shows
that the pot-ball has not been completely ramified by roots and
therefore nothing need yet be done. If the root-ball feels hard
and solid, then re-potting is clearly a matter of priority. Re-potting
is also necessary if you spot tiny flies jumping around on the
surface of the compost. These are feeding on decomposing organic
matter in a compost that has passed its useful life. They disappear
immediately after re-potting.
Most greenhouse plants need
feeding if they are to give of their best. This is most effective
when they are in active growth, either immediately after they
have started to sprout or following the formation of flower buds.
The feeding program is different for individual plant types,
but the exact rates that should be used will be found on the
containers of modern proprietary plant foods. The levels of nitrate,
phosphate and potash are also noted, so that a suitable feed
can be chosen depending upon whether it is to be directed to
fruit and flower production or foliage and root development.
It is important to introduce
a general spraying program to the greenhouse. Irrespective of
the plants being grown, insect pests and fungal diseases will
appear. Check carefully that the fungicide and insecticide mix
so that you can spray in one go. Instructions will be clearly
stated on the package. These will also indicate any plant sensitivity
to the product.
Systemic pesticides are the
only ones that can be used for such a spraying program. These
are absorbed by the foliage, taken into the sap stream of the
plant and serve as an inoculation. To maintain the protection,
spraying will be required every three weeks or so. There are
certain pests and diseases that are not controlled effectively
by systemic products and these need dealing with individually
with contact pesticides. |
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