Growing Magnolias in New Zealand
Taranaki Experience
Our climate is ideal for magnolias with the even rainfall and free draining soil, but the soil is light and its volcanic nature means it is low in phosphates. Varieties such as 'Ian's Red' (from Drury, South Auckland) and 'Genie' (raised locally) which are the reddest varieties in NZ, usually improve in other areas with soils more suited to the nutrient requirements of magnolias. Magnolia Dark Shadow has been tried locally and performed quite poorly colourwise. the following information is based on Taranaki experience, but the basic principles apply to magnolias everywhere.
Magnolia Planting and Care
Planting:
Magnolias are
surface rooting plants, and if transplanting an established seedling or plant
grafted on a seedling, you may notice new roots radiating from the stem above the
older roots. These roots in the natural forest situation where they originate
will grow out through the leafmould on the forest
floor to absorb nutrients released as the fallen leaves break down. As a result
of this natural adaptation Magnolias like a cool root zone so a good mulch after planting will pay dividends. You may have
noticed that magnolias don't thrive until their roots become shaded, either by
themselves, or surrounding companion plants..
When planting magnolias dig in as much compost as possible and work the soil in
an area twice the diameter of the root ball of the plant. Place the plant in
the hole then put in a strong stake before back filling so that the roots are
not damaged by putting it in afterward.
Watch the plant does not get too dry in the first season since magnolias spend
the first year from planting getting settled in, especially if they were field
grown before sale. If they get too dry they will tend to sulk.
If there is some concern about bad drainage, plant your magnolia in a slightly
raised bed so it does not sit in a pool of wet soil. This is particularly a
problem in heavy
If you want to plant a magnolia near water, make sure the plant has 40 - 50 centimetres of well prepared and aerated soil above the
water table to get itself established in. It will appreciate the close
proximity of the extra water, but let it decide how close it wants to put its
roots to it.
When transplanting a magnolia it is best to move as large a block of undisturbed
soil as possible and the resulting stress will be proportionally less. If the
root ball gets disturbed or even shaken out completely, then the plant will
benefit from a reduction of branches by at least a third. Evergreen species
should be root-pruned in autumn before tranplanting,
and deciduous species are best moved when dormant, though they can be treated
as evergreens and root-pruned for shifting in the autumn, as long as their
growth has matured when the root-pruning process starts. If you have to move
one in growth, trim out all the active growing tips, and if possible spray with
an anti-dessicant spray at label rates.
Pruning:
Magnolias generally dont need a lot of pruning, but
if you understand their growth habit they may be modified to fit a smaller
growing space than they would normally require. With careful selecting of
varieties, pruning will also increase the production of pickable flowers.
All magnolias go through an establishment growth phase which is characterised by open upright growth with few flowers
followed by a maturing twiggy phase as the growth slows down to produce a more
horizontal, tiered framework with many more flowers. From time to time they
will also send up strong growths from the base or the main branches. Some
varieties do this more than others, and with grafted plants it is important to
know whether these shoots are from the rootstock or the grafted portion. Leaf
form is a good guide, but if there is any doubt, these shoots should be
removed. These shoots can produce a secondary leader with a very tight fork,
which if left to develop can create a weakness that will sometimes split out in
strong winds and damage the tree severely. Newly planted magnolias will often
produce this type of strong growth in the second or third year from planting,
showing they have settled in and are ready to build their branch framework.
When this happens you can either leave the strong growth to develop a vertical
trunk with a more even framework than the original plant, or if you are happy
with the original structure, you should remove them as soon as they appear.
Redeveloping the framework takes about three years or more but it is well worth
the effort to enhance the elegant stature of the tree as it matures into a
formal framework.
In the first year the older part of the tree should be pruned by about a third
to encourage more vigour into the new shoot, and each
year after that the old framework should be pruned to allow the new structure
to develop evenly. In the second or third year, the old portion may be removed
completely, once the new frame is about half the total framework of the tree.
Be sure to seal the cut with pruning paste to prevent rot entering.
When older trees produce these vertical shoots they will grow upwards till they
reach the canopy then branch out and settle down to flower. If the tree needs
to be reduced in size then it can be pruned back to these shoots and pruning
paste applied to seal the cut. These shoots will mature faster when the tree is
pruned to give them more light.
The overall size of a
magnolia can be limited by annual pruning immediately after blooming. As long
as the twiggy flowering wood is left and the long shoots and any dead wood is
removed, the flower display is maintained on a compact tree. On some varieties
this annual prune encourages the tree to produce stems which have up to six or
eight flowers spaced along them, Apollo, Iolanthe, Denudata and SanJose being among
these types.
Alternately magnolias may be limbed up to make shade trees or even timber
trees. It is a little more difficult to limit the bushier types to a single
stem, but as long as you remove undesired shoots as soon as they appear, they
will respond to training.
Fertilising Magnolias:
Magnolias generally
dont need much feeding once established, but an
annual application of well rotted compost, in addition to mulch, will encourage
strong healthy growth, and increase the moisture retention in light soils and
lower rainfall areas. Addition of Potassic Superphosphate is advisable in light Taranaki soils as
Phosphate tends to be locked in our soils. We get enough nitrogen in our rain.
Mulching fallen leaves with a lawnmower and placing this around the root zone,
in addition to spring mulching, will help recycle nutrients added in previous
years.
Picking Magnolia
blooms for indoors:
A magnolia flower
is at the right stage for picking when the stigmatic column in the centre of a
magnolia flower (upper portion that looks like a pineapple top) shows a slight crystaline look, which means it is still receptive to
pollen. The lower portion of purple and white striped anthers
are still tightly closed. At least one tepal (technical term for what
look like petals on magnolias) should have opened slightly away from the bud as
the opening process begins. In warm weather magnolia flowers will open very
quickly.
Annual pruning also produces flowers with straight stems suitable for picking.
Some varieties respond better as cut flowers than others, with Heaven Scent lasting
up to nine days in a vase. We often enjoy the beauty of magnolias inside by
picking them when they are first opening,with
at least one or two tepals unfurled. At this stage the top of the stigmatic
column in the centre of the flower should still have a glistening look about it
which means it is just opening and still female receptive. They should be put
into water as soon as they have been cut, and if in not too hot a place, will
last a week or more in water, depending on variety.
Magnolias are
generally trouble free garden plants. The commonest problem is bacterial leaf
spot which appears on the new growth in the earlier part of the season while
conditions are warm and moist. Some varieties are much more prone to it than
others. This is best controlled by a copper spray in winter, followed by copper
sprays 2 - 3 weeks apart at summer strength while the plants are putting on
their spring growth. If you grow potatoes or tomatoes and spray to prevent
blight, just mix up a little more spray and do your magnolias if this is a
problem for you.
Another problem is borer. Keep an eye out for the tell-tale dark holes on the
stems, which sometimes weep if water is getting in, and the accumulation of
white frass, which is actually fine "sawdust"
that has been excreted by the grub.
A problem which occurs sometimes is a blackening and death of the stems
associated with a strange fermenting smell when examined closely. Sometimes
half of the tree may be infected, but very rarely is it completely fatal.
Again, some varieties are more prone than others, and unfortunately it is often
grafted varieties where seedling rootstocks are more susceptible to the root
problems. This problem is generally associated with poor root conditions as a
result of bad drainage or root damage, as well as low fertility. Good soil
preparation and site selection as well as adding as much compost as you can,
followed by annual mulching will avoid this problem.(see planting hints)
Look at the magnolias
growing in your area and see which types are doing well. The friendly staff at
your local garden centre will also be able to help you choose the one that will
bet suit your situation. There are new varieties being released from time to
time, so try some of these new and interesting coloured varieties like 'Felix'
(if you have space), 'Genie', 'Sunsation' and
'Burgundy Star'.
Magnolia varieties in
the current collection (landscaped into a 1500 sq metre
valley):
Click here for a page with the current collection with some photographs and brief comments on each. In general, the yellow hybrids tend to be timber trees.
Visit this site to look
at the wider range of magnolia projects:
www.magnoliagrove.co.nz
hits as of 01/07/07