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Pruning Wisteria and some shrubs
Our Garden Design Forum has proved to be a
very popular way in which gardeners can ask expert garden designers for advice
and tips. This page contains some short articles from ourselves that have been
sent to customers as part of our advisory service and that we feel should be an
integral part of our Garden Design Forum. Where we have found articles by other
professionals that we believe can help you, we have also included a link.
Page One - Pruning
- Pruning Wisteria
- Proper Pruning Techniques
(Texas A&M University)
- Training and Pruning Fruit
Trees (North Carolina State University)
- Pruning Flowering Shrubs
(University of Minnesota)
Pruning Wisteria
Planting wall shrubs and climbers
After preparing a
planting hole 3ft (1m) square and 9in (23cm) deep, and adding organic material
to a further 9in (23cm) of depth and to the soil removed, the plant should be
planted 15-18in (40-50cm) away from the wall or fence and leant back towards
it. This is done to ensure that the plants are not starved of moisture as is
often the case when they are planted closer to a wall.
The foundations of
walls absorb moisture and, like fences, deflect rain away from their bases; the
12in (30cm) of soil surface directly below the wall or fence can become very
dry at any time but particularly in the spring and early summer, both critical
times in plant establishment and growth.
We want, and expect, climbers and
wall shrubs to reach substantial heights, but without constant moisture this is
not possible. As the plant grows it will also gain stem girth at the base and
if planted too close to the wall or fence this may be restricted or damaged.
In some cases it may not be possible to prepare a round or square hole
because of paths or other obstructions in close proximity to the proposed
planting position. In these cases the hole can be dug lengthways along the wall
or fence until the recommended square yard (square metre) per plant is
prepared. In some cases it may be possible to remove a paving slab or cut away
the obstruction; even realigning the path might be worth consideration.
Should none of these alternatives be possible, then excavating under the
obstruction and infilling with prepared soil may be possible but care should be
taken not to cause subsidence.
Pruning
Possibly the
question most asked by the gardener is how to prune a Wisteria to make it
flower. Before this can be described fully, one or two points must be explained
and possibly the most important is the selection of the right Wisteria plant in
the first place.
Wisteria grow very easily from seed but regrettably the
resulting flowering, often some eight years after planting, is very variable,
not only in the time they take to flower but in size and, more importantly,
colour. Plants raised in this way should be avoided, even though they appear
less expensive than the alternative, more reliable, grafted varieties.
To
add to the confusion, even the basic form, Wisteria sinensis, may be grown from
seed to grafted, and the only way to be sure is to purchase a grafted named
variety or to ask the supplier which propagation method was used, if he does
not know, do not buy.
Next the growing aspect: it is important that
Wisteria is given a south or west facing position, for without it the shoots
will not ripen and flower buds will not be formed.
You may have a newly
planted Wisteria, say up to one or two years old, or a well established
Wisteria, planted some years ago but never pruned and somewhat out of control -
a very daunting pruning task. Although the two ages require different pruning,
the aim in both is to achieve a vine like shoot formation on which the flower
buds will form over the are allowed for its total maximum growth.
Pruning a newly planted wisteria
In the late mid to late spring
following planting (which should have been, most importantly, carried out as
recommended in Chapter 1) pruning can start - or, more rightly, training can
begin. A formation of horizontal shoots at regular intervals growing out from a
central upright main shoot is the aim.
Even though it may seem harsh and
it will appear that the height of the plant just purchased is being cut away,
in early to mid spring of the year following planting the main shoot is cut
back to within 18in (50cm) of ground level. Should the plant have more than one
main shoot then choose the strongest and remove the remainder completely. If
the main shoot is not 18in (50cm) tall then just tip it, removing the terminal
bud, but in all cases cutting it is important to prevent it from becoming
dormant and shy of growing.
Normally when the plant is supplied it will
have at least a 3ft (1m) bamboo cane supplied with it, which should be replaced
with a 6-8ft (2-2.5m) one, and this should be tied to the horizontal support
wires with soft fillis twine using a figure of eight knot (see Chapter 3).
In the spring and summer following the first cutting back at least one strong
upright shoot will develop and as it grows it should be tied to the cane. If
more than one develops the strongest is chosen and the others removed. By early
summer the chosen shoot will have reached 6-12in (15-30cm) above the first
training wire and is stopped at a bud 3-6in (8-15cm) higher than the wire. If
it has not reached the first wire, pruning is best left until the spring of the
following year.
From below the point at which the shoot is pruned a number
of shoots will emerge. The first of these is tied vertically to the upright
bamboo cane. The next two are tied left and right along the first horizontal
training wires, and any surplus shortened back to 12in (30cm) in summer and
then in winter reduced again to two buds or 2-3in (5-8cm) from the point of
origin.
Should side shoots be formed off the selected horizontal shoots,
these also should be shortened back to 2-3in (5-8cm) in the summer and winter;
it is from these shortened back shoots (spurs) that the first flower buds will
form for display in future years.
Depending on the weather and soil
conditions the stopping of the central upright shoot may be required again once
it reaches the next wire, and the resulting shoots should be tied in and
trained as for the first wire.
In year two the plant is allowed to grow on
until it reaches 6-12in (15-30cm) above the next wire, when the process is
repeated. By now it may have gained enough root development to reach a number
of the wire levels, and at each it is stopped and trained as before.
As
the side shoots grow along the horizontal wires they are tied in and any
surplus shoots on the main or side shoots are cut back in summer to 12in (30cm)
from their point of origin, and reduced further in the winter to two buds or
2in (5cm).
In year three the same procedure is followed, shortening back
the main shoot when it reaches the upper wires or possibly the full height
required. The side horizontal shoots are tied in and any surplus pruned as
before.
The main framework has now been formed and only the horizontal
side shoots will require further training and tying in.
Normally from year
four onwards the Wisteria will be in flower, but without the training suggested
it could be at least eight years and often longer before it comes into
flower.
Routine training and pruning can now start and will be covered
after the explanation of the pruning for an out of control Wisteria.
Always tie the shoots of the Wisteria to a bamboo cane or wires using soft
three-ply fillis twine and the figure of eight knot described in Chapter 3.
Pruning an out of control and overgrown Wisteria
A
Wisteria may have become overgrown from neglect, apprehension of causing damage
or the sheer size of the problem. With the right approach the plant can be
brought back into full flower production and generally have its appearance
improved, while at the same time bringing it under control and reducing the
work required in the following years.
At the first inspection there will
appear to be a maze of intertwining shoots that form no real pattern and first
task is to identify the ones that will form the main framework. Ideally this
will be one major central shoot but ore often two or even three have to be
selected due to the lack of previous pruning and training. Care needs to be
taken to locate any dead or partially damaged shoots that have been
strangulated by the intertwining shoots or bad tying-in, and these are not
always clearly visible at first sight.
As the pruning progresses, training
wires, if non-existent or in poor condition, will need to be provided or
replaced (see Chapter 3).
Starting at ground level and working upwards,
the main shoot or shoots are tied to a 6-8ft (2-2.5m) cane, which in turn is
tied to the support wire. In some cases this may be of a temporary nature until
the pruning is complete. As suitable side shoots growing off the vertical shoot
are located, they are tied out on to the horizontal wires. This may entail
lifting, lowering or bending some to fill a particular position.
Any
surplus side shoots are cut back to 12in (30cm) of their origin in the summer
and further reduced to 2in (5cm) in winter. The process continues until the
full height of the plant is reached. The selected side shoots are also trained
and tied out until they cover as much of the area as required.
In some
cases the pruned Wisteria may not cover the same area that it did before
pruning but it will quickly make up any deficit in the following spring and
summer as new side growths are formed.
A great quantity of surplus shoots
will be removed but the pruner should not be alarmed.
The work can be
carried out in late summer and autumn but as long as there are no hard frosts
it can also be done in winter, and often this is the best time as the shoots to
be retained or removed are more clearly seen.
The Wisteria is now ready to
receive routine annual pruning.
Routine annual Wisteria pruning
From the main stems and horizontal side shoots, through spring
and summer, numerous side shoots (tendrils) will grow and it is the shortening
back of all of these, each year, that produces the flower buds for future
years.
Therefore the more shortening, the more flowers, but it takes
upwards of two years for the remaining buds to form into flower buds. As the
shortening is practised every year, 'flowering spurs' are formed, and care must
be taken to ensure that these are not damaged in any way.
The pruning or
shortening is best carried out in two stages, first reducing them to 12in
(30cm) long in midsummer or late summer, and then finally to 2-3in (5-8cm) or
two to three buds in winter at any time as long as the weather is not too cold.
It should then be done annually.
Wiring the walls or fences
The best way to support a wisteria is to provide it with wires.
To achieve this first use 4in. long screwed vine eyes. Wherever used they
should not be more than 6ft apart and always in a straight line. In houses
older than 1950 it may be necessary to secure into the bricks. After this time
most mortar courses can support the vine eye.
Place the first line 18in
from ground level with additional wires every 18in or so. Supplying wires at
18in spacing until the top of the wall is reached. With Wisteria insure any
wire above a door or window is 18in above it.
The wire can be galvanised
or plastic coated. It should be thick enough to take the weight of the plant
but also flexible to work with. Hardware shops and farm supply outlets are
possibly the best places to find both wire and vine eyes.
Pruning
knives
A good quality pruning knife will be required, to remove
thin weak shoots as well as to pare, or smooth off, the edges of pruning cuts
that are larger in diameter than your thumb. This is done to assist the healing
process and seal the cuts by aiding the production of a layer of new tissue by
the growth cells in the cambium layer just below the bark. Once formed, this
growth barrier can keep out infections such as canker on Apples and Pears,
silver leaf on Cherries and Plums and fireblight on Cotoneasters.
In
addition, Heal and Seal pruning compound should be applied to protect the cut
from attack by fungus diseases such as coral spot. Whereas some would argue
that this is no longer required, I believe it is particularly important on
slower growing ornamental trees, shrubs and climbers.
Secateurs
For larger cuts, Secateurs will be required and these come in two
types; parrot bill, where the upper, sharpened cutting blade cuts down across
the lower, unsharpened, anvil blade; and anvil, where the thinner, sharpened
upper blade cuts down on to the lower, thicker and wider, unsharpened anvil
blade.
It is said by some that the normally more expensive parrot bill
type makes a better cleaner cut and prevents bruising of the stem, but I have
found that if both types are well maintained and kept sharp, there is little
difference, except for the higher price of the parrot bill type.
However,
the following rules apply to both types to ensure a good clean cut and prevent
damage to the Secateurs. Firstly the upper, sharpened blade should always be on
the top or front side of the cut so that the cut is made smoothly downwards or
forwards and with the minimum of sideways movement. Secondly it is important
never to attempt to cut material that is too thick; never try to cut shoots
thicker than can be fitted between the blades when fully open and never nibble
or attempt to cut a branch in stages from different sides. Also, never force
the cut by placing sideways pressure on the Secateurs, as this is a major cause
of permanent damage to both types of Secateurs.
Long-handled
loppers
Should the shoots be too thick for Secateurs it will be
necessary to use a pair of long-handled loppers, which have more leverage.
These also come in two types, parrot and anvil, and the same rules of use apply
as for Secateurs.
Folding saws
As an alternative to
loppers, and in some cases Secateurs, my choice is to use a folding pruning
saw; I find that with its 6-9in (15-23cm) blade it not only cuts the larger
material and does it very cleanly, but because of its narrow and short blade it
can reach into difficult confined spaces.
As it cuts on both strokes,
backward and forward, care must be taken, as always, to prevent accidents from
the very sharp teeth.
A good sharp folding saw can make as clean a cut as
the best Secateurs.
Bow saw
There may be times when
the folding saw is not adequate for the job, and then a bow saw will be needed.
Although it can sometimes be difficult to position due to its size, it is
useful for the removal of larger branches, particularly on trees.
Chain saw
I advise strongly against using a chain saw, for not
only can it be very dangerous when used by an untrained operator in confined
spaces, but if used indiscriminately it can cause a great deal of damage to the
tree or shrub being 'pruned'.
Sharpening of pruning tools
All tools should be kept clean and sharp, and if a lot of work is carried
out in the garden each year, replacement tools, in particular Secateurs, may be
necessary. The sharpening of knives and Secateurs is best done using a
household or workshop chisel sharpening stone, which can be purchased from most
DIY stores. It will normally have hard and soft sides and will be 4-5in
(10-12cm) long, 1in (3cm) wide and ½in (1cm) thick. Before use it should
be moistened with water or a small amount of household oil. The cutting edge of
the blade is drawn, three or four times, slowly and firmly over the stone at an
angle of 25-35°, ensuring that the bevelled edge of the blade is facing
down on to the sharpening stone. To finish off, one pass is made over the stone
on the reverse side to remove any 'burr' - the small pieces of metal that may
have formed.
If this sharpening process is carried out with a new knife or
Secateurs, the soft or smoother side of the stone is used. Sharpening should
then be repeated at regular intervals during use.
Should the knife or
Secateurs have been neglected, three or four passes over the hard or rough side
may be best, finishing off with two or three passes over the soft or smoother
side, plus the reverse pass. If more than this is required it is probably best
to purchase a new tool.
Loppers do not normally require sharpening, but
from time to time passing the hard or rough side of the sharpening stone over
the leading edge of the cutting blade may be of assistance and will help with
the final cleanness of the cut.
Saw blades are best replaced as necessary,
as to have them sharpened could cost as much, even if you could find somebody
to do it.
Making the pruning cut
Whenever possible,
cutting to above a bud is recommended. Buds are normally the raised points
along a plant's shoots where the new side shoots, leaves and flowers will be
produced. They may be arranged opposite each other or alternatively along the
length of the shoot, normally at regular intervals. They contain all the
plant's potential for producing new side shoots, foliage and flowers in the
spring, summer and autumn following pruning, so care is needed to avoid
damaging them.
When the plant is, say, more than three years old, the buds
may be harder to see, having become camouflaged by the bark. But even if they
cannot be seen, they are still there in a dormant state and once pruning has
been carried out they will be induced to grow and produce new growth. When
pruning, a calculated guess may have to be made as to their position.
If
the buds can be seen, the cut should be made above and within ¼in (5mm)
of the bud. If the cut is not made cleanly or at the right angle, there is
always the chance of dieback; this is caused by rain entering through the
pruning cut and inducing rotting, which can spread and cause further damage.
Alternatively it can be caused by the pruning cut being made too high above a
bud so that plant foods in the form of sugars are not used and all the surplus
food above the bud will rot. Once the fungi have a hold, they spread down the
stem in search of more food and start to kill the plant tissue in order to
obtain food in a form they can use. With some species of shrubs, in particular
Acers (Maples), coral spot fungus may gain a hold under these conditions, as
will cankers of various trees in the Malus (Apple) family.
So a clean cut
is made with a sharp pruning tool at an angle sloping away from the bud to
ensure the run-off of rain, and just far enough above the bud to avoid it being
cut or crushed. If the cut is larger in diameter than your thumb, it should be
pared off (the edges of the cut trimmed) with a sharp knife and painted with
Heal and Seal to prevent the entering of diseases.
Tree-pruning
hygiene
To prevent the build-up of over wintering pests and
diseases the application of a winter tar oil wash is good garden practice, to
eliminate the eggs and spores of the pests and diseases that attack and spoil
fruit. The wash also improves the appearance of the bark of trees or bushes by
making it shine and for this reason it is very effective when used on
ornamental trees as well as fruiting varieties.
The directions on the
product should be closely followed and health and safety requirements complied
with.
Personally I am not in favour of shredding pruned shoots, as there
is always a risk of spreading pest and disease infestation, nor do I like to
use the shredded material for soil mulching or improvement, for the reason
stated in Chapter 2. All pruning material should always be removed and burnt as
soon as possible.
Removing large shoots and branches
If a large shoot is to be removed using a saw, folding or bow, it is good
practice to make the first cut 2ft (60cm) away from the intended final cut, so
removing some of the weight. To help make a clean final cut, approximately a
third of the diameter of the shoot is cut with the saw from the underside
upwards. A cut is then started from the top, ensuring it is in line with the
lower one, and the remainder of the cut made.
Geographical
differences in pruning times
Throughout the following text,
reference is made to the timing of pruning, based on the southern and central
area of the United Kingdom. For those gardening in the southwest, the work can
often be brought forward by seven to ten days. In the north, Northern Ireland
or Scotland, it may need to be delayed for a week or two, but in all areas,
account should be taken of weather conditions, and if in doubt wait until the
weather improves.
Tying materials
It seems that
whenever industry produces a new or waste product that might be used as a tying
material, particularly if it is coloured green, it is offered to gardeners
without any tests being done or consideration being given to the damage it may
do to a plant by strangulation.
With the possible exception of perennials,
all plants require ties that can expand, can be adjusted or will rot within a
year to prevent damage.
Recommended soft tying materials
- Three-ply fillis string (untreated)
- Raffia, although this is more expensive
than fillis string
- Small and large adjustable rubber or
flexible straps, ensuring the size is adequate for the tree and that all are
supplied and fitted with a buffer to avoid rubbing between the tree and stake;
whenever possible, purchase the straps loose rather than pre-packed, as they
are often cheaper.
Tying materials to avoid at all costs
- Polypropylene string
- Binding twine
- Wire
- Plastic tying material that does not
stretch as the plant grows
- Rubber and plastic ties of the interlocking
chain type
- Fillis and other soft strings and twines
that are treated with creosote or green tannalized to prevent rotting.
- Modern tights and stockings produced from
material that does not rot.
- Figure of eight knot
Over the years I have tried a number of
different knots and ways of attaching plants, other than trees, to their
supports, but the safest and most effective way has always proved to be the
figure-of-eight knot where the fillis string is looped around the cane, support
wire of individual anchorage point, crossed over itself, looped around the
front of the plant and secured and tied with a reef knot, allowing just enough
slack to prevent restriction and strangulation.
If the plant is being
attached to horizontal or vertical wires or to canes, slipping will be reduced
by making a second loop around the wire or cane.
These ties are intended
to rot and need replacing from time to time, so regular checks should be made
to ensure that the plant is secure and is not being damaged by movement caused
by the weather.
© Copyright Brian Davis
Click
here for the full Texas A&M University article.
Follow Proper
Pruning Techniques
Proper pruning enhances the beauty of almost any
landscape tree and shrub, while improper pruning can ruin or greatly reduce its
landscape potential. In most cases, it is better not to prune than to do it
incorrectly. In nature, plants go years with little or no pruning, but man can
ruin what nature has created. By using improper pruning methods healthy plants
are often weakened or deformed. In nature, every plant eventually is pruned in
some manner. It may be a simple matter of low branches being shaded by higher
ones resulting in the formation of a collar around the base of the branch
restricting the flow of moisture and nutrients. Eventually the leaves wither
and die and the branch then drops off in a high wind or storm. Often, tender
new branches of small plants are broken off by wild animals in their quest for
food. In the long run, a plant growing naturally assumes the shape that allows
it to make the best use of light in a given location and climate. All one needs
to do to appreciate a plant's ability to adapt itself to a location is to walk
into a wilderness and see the beauty of natural growing plants.
Pruning,
like any other skill, requires knowing what you are doing to achieve success.
The old idea that anyone with a chain saw or a pruning saw can be a landscape
pruner is far from the truth. More trees are killed or ruined each year from
improper pruning than by pests. Remember that pruning is the removal or
reduction of certain plant parts that are not required, that are no longer
effective, or that are of no use to the plant. It is done to supply additional
energy for the development of flowers, fruits, and limbs that remain on the
plant. Pruning, which has several definitions, essentially involves removing
plant parts to improve the health, landscape effect, or value of the plant.
Once the objectives are determined and a few basic principles understood,
pruning primarily is a matter of common sense.
The necessity for pruning
can be reduced or eliminated by selecting the proper plant for the location.
Plants that might grow too large for the site, are not entirely hardy, or
become unsightly with age should be used wisely and kept to a minimum in the
landscape plan. Advances in plant breeding and selection in the nursery
industry provide a wide assortment of plants requiring little or no pruning.
However, even the most suitable landscape plants often require some pruning.
The guidelines presented in this publication should be helpful when pruning any
plant.
© Copyright Texas A&M University
Click here for the full
North Carolina State University article
Training and Pruning Fruit
Trees
Growers often neglect the annual training and pruning of fruit
trees. Without training and pruning, however, fruit trees will not develop
proper shape and form. Properly trained and pruned trees will yield high
quality fruit much earlier in their lives and live significantly longer.
A
primary objective of training and pruning is to develop a strong tree framework
that will support fruit production. Improperly trained fruit trees generally
have very upright branch angles, which result in serious limb breakage under a
heavy fruit load. This significantly reduces the productivity of the tree and
may greatly reduce tree life. Another goal of annual training and pruning is to
remove dead, diseased, or broken limbs.
Proper tree training also opens up
the tree canopy to maximize light penetration. For most deciduous tree fruit,
flower buds for the current season's crop are formed the previous summer. Light
penetration is essential for flower bud development and optimal fruit set,
flavor, and quality. Although a mature tree may be growing in full sun, a very
dense canopy may not allow enough light to reach 12 to 18 inches inside the
canopy. Opening the tree canopy also permits adequate air movement through the
tree, which promotes rapid drying to minimize disease infection and allows
thorough pesticide penetration. Additionally, a wellshaped fruit tree is
aesthetically pleasing, whether in a landscaped yard, garden, or commercial
orchard.
© Copyright North Carolina State University
Pruning
Flowering Shrubs
When deciding to prune shrubs, timing, is usually the
most important factor to consider. With flowering shrubs, when it flowers and
whether it flowers on old wood or new wood will determine when to prune. Old
wood is wood that has gone through at least one winter. New wood is the part of
the branch that has grown in the current growing season. Shrubs that bloom
early in the growing season on old wood such as azaleas, forsythias, lilacs,
and Juneberries should be pruned immediately after they finish blooming. Shrubs
such as mock orange, potentillas, roses and weigela that flower later in the
year, on new and old wood, should be pruned before growth starts in the spring
or after blooming. Prune shrubs that flower on new wood before the growing
season begins. Most of these shrubs should be pruned to the first pair of buds
above the ground. Examples of these include most clematis, Annabelle and Peegee
hydrangeas, and Anthony Waterer spirea. Fruit bearing shrubs like barberry,
buckthorn, dogwood, honeysuckle, and viburnums should all be pruned in the
spring before growth starts. When only the tips of branches are pruned, the
shrubs become overgrown and lose leaves on the lower branches. Overgrown shrubs
will have leaves only on the outer branches and bare branches in the center. To
prevent this, about 1/3 of the oldest branches should randomly be removed each
year. This will allow for new branches to grow from the base and allow leaves
to grow throughout the entire plant. Most evergreens such as junipers and yews
can be pruned at any time although early in the year is best. Evergreen shrubs
in the pine family such as Mugo pines can only be pruned when they are at their
candle stage in the spring. These candles, or new growths, can be cut back by
1/3 to 1/2 of the length. Cutting past the candle or pruning at the wrong time
will result in dead stubs.
© Copyright
University of
Minnesota
If you would like to discuss the
work of the Associates further and arrange a visit by one of the Associates,
please contact:
Hugh O'Connell, APLD, Managing
Director, English Garden Design Associates, The Annexe, Ponchydown Farm,
Blackborough,
CULLOMPTON, Devon, EX15 2HQ, UK
Telephone: +44 (0) 1884
266188
Fax: +44 (0) 1884 266188
Email:
hugh.oconnell@btopenworld.com
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