Agriculture Reference
In-Depth Information
The snowball tree,
Viburnum opulus sterile
,
is, as its name suggests, sterile and produces
no seed. It is grown from stem cuttings as it
can grow adventitious roots. Adventitious
roots do not arise from a seed but from a
piece of stem, leaf or branch inserted into
a suitable growing media. This has
advantages. An adventitious root system,
instead of growing a vertical tap root,
produces many roots that grow more
horizontally. This allows better access to
nutrients in the richest top section of the soil
profile and also indicates an ability to recover
from root damage.
but there will be individuals that have the
genetic traits required for coping with
differing conditions.
However, in ornamental landscapes where
uniformity of growth is desirable, never use
seedlings. The same can be said for food
plants such as fruit trees. Fruit trees grown
from seed are unreliable. They may take up to
20 years to fruit, in the case of avocados, and
the fruit may not be worth gathering when it
is produced. Take advantage of our
agricultural heritage of millennia of selective
breeding. Purchase a known cultivar for
guaranteed fruit production.
Implications for pruning
Grafted plants are in fact two to three plants
on the one root system. If the plant is cut off
below the graft or throws up suckers from the
root system this growth
will not be
of the
desired cultivar. It should be removed or
regrafted with the desired scion wood.
Stakingplants
Staking plants has become a bad habit in
horticulture and rarely, if ever, is a well-
staked plant seen. There are a few good
reasons for staking plants, but this technique
is over-used to the detriment of the plant
material concerned. Like over-indulged
Western children who are not taught to be
self-reliant, a plant that is used to being
propped up will become unstable when the
supports are removed. Most plants do not
need staking and develop stronger root
systems and better height-to-girth ratios
when unstaked. Just as the best tree to
choose at the nursery is wider than it is
tall (see 'Choosing the right plant at the
nursery' on page 15), a tall skinny tree that
develops as a result of over-long poor staking
is unstable.
Plants grown from cuttings are one plant. This
means that if the plant is decapitated or throws
up suckers from the root system, it will still be
the desired cultivar that was purchased. It will
also be genetically identical to other plants of
the same cultivar so uniformity of growth for
hedging or avenues is assured.
Seedling-grown plants are variable. They are
essential for biodiversity as each seedling is an
individual with differing strengths and
weaknesses, just like human beings. Their
flowers, bark, branch habit and disease
resistance will vary in each individual. This is
why there is strength in diversity. A genetically
diverse plant base can overcome changes in
the landscape or climate. Not all will survive
Advanced trees will need staking as their root
system needs to be kept stable in the soil. A
stable root system that is not rocked by winds
