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Cultivation Shock....or "Fire and Ice"!

Growing Grevillea in a harsh climate

Ken and Elaine Arnold

We bought "Clearview" at Yeoval, situated on the central western slopes of New South Wales about 50 km due west of Burrendong Dam) at the end of 1995. It is a property of 2.73 hectares, granite country, with a coarse, well drained, very acidic granitic soil which goes as hard as concrete when dry, and is practically humus free. Essential statistics for the area are - average rainfall 614 mm, average maximum temperature 31C, average minimum 1C, hence the alternative title "Fire and Ice"!

The previous owner had fenced off 0.81 hectares around the house and had developed garden areas containing mainly dry country species of Eremophila, Acacia, eucalypts etc. We fell in love with the place at first sight.

We did not intend to take up permanent residence there, so we have used it as a weekender. We quickly realised we had a steep learning curve in front of us - conditions were so different to the well watered, comparatively frost free temperate Sydney scene.

Grevillea alpina
Grevillea alpina (51k)

Grevillea candelabroides
Grevillea candelabroides (51k)

Grevillea decora
Grevillea decora (31k)

Grevillea fililoba
Grevillea fililoba
"Ellendale Pool" (37k)

Grevillea 'Honey Gem'
Grevillea "Honey Gem" (29K)

Grevillea thyrsoides
Grevillea thyrsoides subsp.thrysoides (41k)

Grevillea juncifolia
Grevillea juncifolia subsp.juncifolia (44k)

Grevillea treueriana
Grevillea treueriana (29k)

Grevillea beadleana
Grevillea beadleana (37k)

Grevillea pimeleoides
Grevillea pimeleoides (37k)

Grevillea leptobotrys
Grevillea leptobotrys (33k)

Grevillea rhyolitica
Grevillea rhyolitica (30k)
   

A manually operated watering system, using the town's non-potable water supply, was installed to the garden areas, but it was a plumber's nightmare of mixed fittings of iron, brass and plastic, of varying sizes.

It had to be upgraded, extended and automated if plants were going to survive for us.

We had bought the property just at the end of a dry period and we had quite a few losses in the early days simply because we were not there to water when plants required it.

Everything is bigger in the bush - the storms, the weeds, the spiders and the problems. It took us about twelve months to get a feel for the area.

We visit about once a month. If it had rained we would be flat out "grass" cutting and weeding - if it hadn't we would be madly racing around with hoses to water the trees and shrubs not in gardens and thus outside the watering system.

As to the "grass" - apart from some patches of Kikuyu, the ground cover consists of whatever comes up at the time - barley grass, clover and many other monstrous things we had never seen before!

Finally, in early autumn 1997,after the expenditure of litres of blood, sweat, tears and insect repellent through the preceding summer, the automatic watering system was finished. It was worth the effort to have peace of mind that plants were being watered in our absence.

There are eight separate garden areas, and except for one garden that is watered by a couple of large overhead sprays, all watering is carried out by drippers or small spray jets. We are limited to a maximum flow rate of about 800 litres per hour because of supply and piping limitations. We dream one day of having a pressure-boosted system but that is a long way off in the future.

Keeping the weeds down appeared to be a huge and never ending problem. Mulching proved to be the answer, but we could only get it in 2m3 loads in our box trailer from either Orange or Dubbo, and that chore effectively disposed of one day.

A load of 2m3 disappeared very quickly on the large areas we needed to mulch. Finally, after several loads, in spring 1998 we located a carrier who would bring us a big load - 23m3 in fact!

Such is the tyranny of distance in the bush; cartage cost three times as much as the cost of the mulch! It was worth it though, both financially and in its practical benefits. We have spread about 80% of our big mulch heap of Callitris chips, and we feel that we are finally getting a little bit in front of the weeds.

Winter 1997 was interesting - the district had a "thirty-day frost" - frost every morning for 30 days and no rain in this period. Strangely, it was the larger shrubs and trees that were most affected. Trees that had been established in the district for years were either badly burnt or even killed.

The winters of 1998 and 1999 were reasonable, with only some tip damage to shrubs, and rainfall was fairly consistent, with a couple of short dry spells. But the winter of 2000 was a killer! Not a lot of frosts, but some really deep ones - an adjoining hamlet about 20 km away recorded -8C! I'm sure we had just as bad, as we have lost quite a few robustly growing shrubs, killed stone dead!

Frost is a funny animal - you never know quite what the effect will be from year to year. What gets hit one year will be untouched other years - some plants can be completely defoliated and yet still bounce back, whilst others will struggle through a couple of winters until finally succumbing. A plant in one area will be badly affected but the same plant elsewhere will be untouched!

We are still refining our planting techniques, but generally follow the same procedure with all plants, Grevillea or otherwise. A planting hole about 3 or 4 times bigger than the plant container is dug and a good handful of gypsum is incorporated into the soil, with possibly some coconut "peat" if the site is a particularly miserable one. All holes receive a dash of water retaining crystals before soaking with water containing root hormone and Aquasol, together with wetting agent if the soil is particularly dry.

Even though the soil is very acid (pH 4 to 5), we have been reluctant to use any lime (dolomite) unless we have definite evidence that the plant being planted prefers a high pH. However, this is a factor that we will experiment with in the future.

When the plant is settled in its chosen spot, it is well mulched with chips and largely left to its own devices. We have had some success rescuing sick plants by spot watering with Seasol. It is expensive, but seems to do a good job.

What have we learned? Mulching is essential - we could write a separate article on the finer details of mulching! We have a fair idea of which areas of our property are worst for bad frost effects. We don't plant in autumn now unless we are really confident of the frost resistance of the species and the situation.

As keen Grevillea fanciers the majority of our plantings have been of this species. We know we can forget about most tropical grevilleas; hybrids appear, generally, to be more resistant to frost than pure species. Available data on frost resistance is sketchy and not really reliable, so we have been prepared to take a chance!

Our disappointment over losses is tempered by unexpected successes. The natural occurrence of species of any genus is not necessarily a guaranteed indicator of frost performance, so we give it a go!

The sub-title of this article is "Fire and Ice" - we can deal with the Fire part with water, but Ice can take a lot of beating and we are still learning!

The following list of Grevillea species that is growing, or have been grown, at Yeoval is given an arbitrary frost rating of 1 to 5. I do not assign temperatures to these ratings as I do not have the means to accurately provide the hard data, but nevertheless it can be a handy guide to Grevillea growing in colder climes. Some plants may be given more than one number and this probably reflects the variability of winters and growing situations, rather than variable response in the plant itself.

Explanation of the rating scale

  1. Excellent, little or no effects.
  2. Slight effects such as tip burn, no permanent damage.
  3. Moderate foliage and structural damage requiring pruning clean-up when growth restarts.
  4. Extensive defoliation, stem or limb splitting, recovery doubtful.
  5. Death.
  • An asterisk indicates effect in the killer frosts of 2000, but otherwise OK.
  • The 5** rating for Grevillea pimeleoides is an interesting case. We had four plants of this species, one graft and three on their own roots. One of the plants on its own roots was a chance purchase made locally, and it was planted autumn 2000. Winter 2000 killed it stone dead very early in the winter period, and the three other plants were untouched, so obviously provenance, hardening off etc, has a big influence on frost resistance.
  • An upper case "G" after a species indicates a graft.
SpeciesRating SpeciesRating SpeciesRating
alpina
aquilifolium
amigera
annulifera
annulifera x leucopteris (G)
beadliana (G)
buxifolia
bronwenae (G)
candellabroides (G)
caliantha (G)
corrugata
confertifolia
curviloba (x6)
deflexa
dryandroides (G)
decora
dielsiana
eriostachya (G)
"Ellendale Pool"
flexuosa (G)
1
1
1
5
2
2
2
2
1
1
1
1
1
1
1
5
5*
4 & 5*
2
1
filipendula
"Forest Rambler"
xgaudichaudii
georgeana (G)
glauca
"Honey Gem"
insignis subsp insignis (G)
juncifolia (both subsp)
juniperina
leptobotrys (G)
leucopteris
longifolia
"Little Thicket"
leucoclada (G)
levis
manglesoides
magnifica (x4)
masonii (x2)
mccutcheonii
maxwellii (x2)
2
1
1
1
5
2 & 5*
1
2
1
2
2
1
1
1
4
1
2
1
2
1
nana (G)
nudiflora (G)
oligomera (G)
plurijuga (G)
pinaster
pythara (G)
preisii subsp glabrilimba
pilosa subsp pilosa (G)
pimeleoides (x4)
rhyolitica
rigida subsp distans (G)
salcata
scortechinii
synapheae subsp synapheae
"Sid Cadwell"
spinosa x juncifolia (G)
thyrsoides (both subsp) (G)
treueriana
wilsonii
"White Wings"
2
1
5*
2*
1
5
1
1
1 & 5**
4*
2 & 4*
1
1
1
1
2
1
5*
1
1


From the March 2001 issue of the newsletter of ASGAP's Grevillea Study Group.

Photos by Brian Walters except Grevillea juncifolia and G.decora, both by Keith Townsend.

Select a thumbnail image or highlighted plant name to view higher resolution images.


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Australian Plants online - June 2001
Association of Societies for Growing Australian Plants