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General planting tips
The following considerations are a general guide for most plant varieties. The
Stocklist pages list individual varieties
and their attributes which may indicate more tolerance to adverse conditions
such as poor drainage, wind, frost etc..
Preplanting care:-
Watering
and holding location
Planting site:-
Drainage
Sunlight
Strong winds
Frosts (-1 Deg. air
temperature or less)
Planting:-
Soil
cultivation and improvement
Soil PH
Transferal
of plant to ground
Fertilising
Mulching
Watering
Grevillea cultivation
Grevilleas generally thrive in low maintenance gardens. It is a fact that many
gardeners who neglect their Grevilleas often have greater success than over
enthusiastic gardeners. If particular care is given to the five points below
your Grevilleas should thrive with little other attention.
Good
drainage
Full sun (Or 50% at
the least)
Mulch well
Water seldom
No phosphate
rich fertilizers or garden soils
Grevillea FAQ
General planting tips
Watering and holding
location
Plants should be held outdoors in a place with similar conditions to the
intended planting site Thorough watering is essential at least once a day
preferably in the morning. If the weather is very hot or the plants are large
in relation to the size of the pot then at least twice a day will be required.
Drainage
If the soil is a sticky clay type or has a shallow clay subsoil. then it should
be built up to improve drainage. Soil which is imported should be used to mound
up the planting site rather than digging a hole to replace the existing soil.
Gypsum may be used to improve the structure of sticky soils.
See also: Stocklist pages for tolerant
varieties.
Sunlight
Most of the product lines prefer anywhere in the range of full sun to 50%
shade. This could mean a full day of 50% filtered sun or full sun for half a
day.
See also: Stocklist pages for tolerant
varieties.
Strong winds
Most of the product lines benifit if sheltered from strong winds. This is
normally not an issue in suburban back yards but may be a problem on exposed
hills etc.
See also: Stocklist pages for tolerant
varieties.
Frost
Many of the Product lines are not tolerant to air temperatures of -1 deg. C or
less. Planting resistant varieties is the best protection against frost.
Plastic film may be used to protect young plants but should be supported to
completely cover the plant without touching the foliage. So called frost
protectant chemicals will not stop frost damage but may reduce wilting
of the plant after the sun rises, particularly if a drying breeze springs up.
The same applies to watering just before sun rises. True frost damage is caused
by liquids freezing within the plants' leaves and no coating on the foliage
short of a perfect insulator will stop this. Likewise, overhead watering will
really be effective only if it is applied the whole time that the air
temperature is below zero.
See also: Stocklist pages for tolerant
varieties.
Soil cultivation and
improvement
Home made compost is generally the best soil improver. Bought composts and
garden soil mixtures are good soil improvers but unless made properly by a
competent supplier may suffer from problems such as high nitrogen draw down
(Low NDI) and levels of phosphorus too high for some phosphorous tender plants
such as Grevilleas & Banksias. Soils which are reasonably friable (i.e.
easily crumbled) generally need not have anything added in the planting hole.
Rather, the hole should be well dug then back filled to give the plant a good
start.
When it is necessary to buy soil because of poor drainage, it should be used to
mound up the planting site rather than digging a hole to replace the existing
soil. This would defeat the purpose by forming a water holding basin. Good
quality sandy loam is probably a more economical alternative to garden soil
mixes for this purpose . Moisture retention of the sandy loam may be improved
by applying liberal quantities of a surface mulch such as sugar cane mulch
which can be purchased with the money saved on the garden soil mix.
Clay loams with marginal friability may be improved by applying gypsum to help
build up crumb structure.
Soil PH
In most cases gardeners should not be preoccupied with lists of
"ideal" PH ranges for individual plants which are often printed in
books as most plants will grow happily in a PH range from 5.5 to 7.5
particularly if a balanced fertiliser is used. At the high end of the range
applications of Iron Chelate or Iron Sulphate may also be beneficial for some
plants.
Dolermite should be added only after the PH is verified to be low either with a
test kit or by a soil testing laboratory and should rarely need to be added for
acid loving plants such as Azaleas. If the PH is high, sulphur may be used, but
it is very easy to poison the soil through over application. Applying Iron
Sulphate in liquid form after planting and possibly at later intervals may be a
safer solution.
Transferal of plant to
ground
Plants should be well watered prior to removal from pot. If the roots at the
bottom of the pot are wrapped around tightly it will be necessary to tease them
out. If very tightly packed use an old pair of scissors to make several
vertical cuts right up the side of the root ball. Some perennial shrubs such as
Callistemon Little John for example may, become root bound when the plant is
only a few inches out of a 140mm pot and will never thrive unless this
treatment is carried out. Grevilleas on the other hand, rarely form a tight
root ball in the pot and are better left undisturbed.
The planting hole should be back filled enough so that the top of the potting
mix sits level with the ground when the plant is placed in the hole. Care must
be taken with plants that have low crowns such as Gerberas to keep the crown
well clear of ground level. The hole should then be filled around the plant and
the whole lot watered in well but not tramped down.
Fertilising
Slow release fertilisers with at least a 9 month release period are the
simplest and most effective way to apply fertiliser. Osmocote 18-2.6-10 is
quite suitable and is best spread on the surface of the soil around the plant
before the mulch is applied.
Mulching
Sugarcane mulch is a good economical and easily spread material. Many other
materials such as forest mulch are also quite suitable but should not be used
too fresh. Slash pine bark is one of the best if a more attractive mulch is
required but is also quite expensive. Bails of straw and reject hay although
sometimes very cheap may introduce new weeds into the garden so do more harm
than good.
Some gardeners spread old newspapers under the mulch to stop weeds coming
through but it is not advisable to use plastic for this purpose
Watering
The regularity of watering will depend on factors such as the soil type and the
weather. However the general rule is, "deep but infrequent". This
means, try to penetrate the soil deeply when you do water but let the soil dry
out a little before the next watering. Most plants will not be damaged by
slight wilting. On the other hand, few plants will tolerate continually sodden
roots. Besides, a healthier plant will be produced if it has to work for its
water a little.
Grevillea cultivation
Good drainage
Deep sandy loam is the preferred soil type. However Grevilleas will also do
very well in clay loams provided there is a good slope on the ground. If soil
is to be imported, it should be used to mound up the planting site rather than
digging a hole to replace the existing soil. Planting in clay soils where there
is little slope on the ground is not recommended.
Full sun
Grevilleas prefer full sun and most varieties require a minimum of 50% during
the growing season for best flowering and strong sturdy growth. Some varieties
are reported to be "Shade Tolerant", e.g. Grevillea Coastal Glow.
Generally however even these varieties will benefit from more sun.
Mulch well
Like most other plants Grevilleas will benefit greatly by liberal applications
of surface mulch spread around the drip zone of the shrub and well beyond if
possible.
Water seldom
When first planted watering should be fairly regular. This may even be required
every day for the first week or two if the weather is very hot and dry. As the
plant becomes more established it should be progressively weaned so that by the
time it is one year old water need only be applied during extended dry periods.
Over watering often results in plants which appear to be growing vigorously but
will die prematurely and without warning. It is better to hold back watering
till the plant shows signs of wilting than to over water. This will not hurt
the plants. On the other hand plants which are over watered may not show any
symptoms until they start to die.
No phosphate rich fertilizers or garden
soils
Because of a specially adapted root system unique to the Proteaceae family of
which Grevilleas are a member, some varieties exhibit an extreme sensitivity to
Phosphorus. Sources of this nutrient which may cause problems include:-
Grevillea FAQ
Q. What do I use to improve
poor quality soil?
A. If soil needs to be imported onto the sight, a straight sandy loam
will yield better results than garden soil mixes and at a fraction of the cost.
Moisture retention of the sandy loam may be improved by using a surface mulch
such as sugar cane mulch which can be purchased with the money saved on the
garden soil mix.
Q. And what about
fertilizer?
A. Fertilizing Grevilleas is not an absolute necessity as they have
adapted to soils with very low nutrient levels. However conservative
applications of a slow release fertilizer low in P and with a 9 month or
greater release period such as Osmocote 18-2.6-10 will improve the growth. We
do not normally recommend the use of zero P fertilizers as even Grevilleas will
benefit greatly from a small increase in P as long as no previous application
has been made to the soil.
Q. What can I do if a rich
garden soil or some other phosphorus source has already been put in my garden
and I still want to plant Grevilleas?
A. The effect of added phosphates will depend very much on your base
soil type. A very light sandy soil will be more prone to phosphorus toxicity.
On the other hand some special types of clay soils fix phosphorus so
effectively that no problems will be experienced even with relatively large
applications of phosphates. In any case the first effect of P toxicity will
actually manifest as iron deficiency. This will show up as a yellowing between
the veins of the active new growth. Quite often the deeper green of the veins
is not noticeable and the yellowing of the new growth seems more general.
Fortunately, provided the P toxicity is not too severe it can be treated very
effectively at this stage by applications of iron. Since iron is only a trace
element, it is not normally applied at large rates. However, as well as being
essential for plant growth in small quantities, iron also has the effect of
deactivating phosphorus both in the soil and the plants metabolism. If P
toxicity is evident we recommend that the soil around the plant be drenched
with a 1 gram/litre ferrous sulfate solution (approx. 1 flat teaspoon in a 10
litre watering can). This may be repeated after two or three good waterings.
For the first application only this rate may be doubled provided no other
soluble fertilizers have been used and there is no salinity problem with the
soil or the water. However, the plant should not be allowed to dry out to
severely after an application.
Q. Why did my Grevillea which was
growing so well drop dead over night?
A. The normal cause of this is over watering. Plants growing in poorly
drained soil do generally not thrive at all, although an unusually wet season
may be responsible for the death of a previously healthy plant if the drainage
is marginal. Automatic watering systems are not a good idea for Grevilleas even
though the regular watering initially seems to produce a healthy vigorous
plant. There are also many less commonly grown varieties which are more prone
to root rot and may die for no apparent reason. These varieties should only be
grown by grafting onto a hardy rootstock such as Grevillea Robusta (Silky Oak).
Q. What is the black sooty mold
that grows on my Grevilleas?
A. This is a non parasitic mold that grows amongst the tiny hairs on the
stems and underside of the leaves. Although it can reduce the growth of the
plant if severe, it is often blamed for a sick looking plant which may have
other problems. The sooty mold simply looks worse when the plant is not putting
on any new growth. This mold will always be present to some degree on
Grevilleas. It may get worse in humid and rainy weather and is also encouraged
by populations of sucking insects such as jassids. However if the plant is in
good health it is not generally noticeable.
Q. When and how hard can Grevilleas
be cut back?
A. In Spring, or after the main flowering has finished is the best time.
At most no more than 70% of the foliage should be cut off and there should be a
good number of healthy looking buds about to shoot on the branches which are
left. Grevilleas will not take being cut back to a bare stump like some other
Australian natives such as Melaleucas.
Disclaimer:
The information provided on this page is intended as a guide only and Eureka
Nursery accepts no responsibility for the use or misuse of this information.
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