Hardy Banksias for Alkaline Areas
4 Comments »18th June, 2006; Category: Banksias
Banksia praemorsa
I found a photo of one of the Banksias to update this post. Banksia praemorsa is a good hardy plant which has a few different colour forms. My favourite is a wine coloured form which I do not see very often.
These Banksias seem to grow quite well in alkaline soils with good drainage. If plants seem unthrifty I try some agricultural sulphur, a cupful to the square metre, watered in because the soil here is highly alkaline. Failing that, some iron sulphate, or iron chelates (following packet directions). Good garden practice would see lots of organic matter going into the soil which would lower the pH a little over a period of time.
Banksias for difficult soil…
Banksia ashbyi
Banksia baueri
Banksia caleyi
Banksia coccinea (needs limestone subsoil)
Banksia ericifolia
Banksia grandis
Banksia integrifolia
Banksia marginata
Banksia media
Banksia ornata
Banksia praemorsa
Banksia prionotes
Banksia speciosa
Banksia victoriaeSome of these are in this list because of anecdotal evidence that they will grow in alkaline soil. More will probably be added as they are trialed by folk willing to have a try with the species.
Growing Banksias
Having written about the frost hardiness of Banksias, I thought I would look at the general growing conditions.
There is a number of species which do very well in the alkaline soils locally and once established, manage on the local rainfall of 334mm a year, falling mostly during the winter.
The first requirement is good drainage. This can be achieved by raising the planting area by as little as 10cm, more would be safer, if this is a problem. An issue for me is that some parts of the block have little top soil and a planting hole can become a sump 9or like a plasti c pot without drainage holes) when there is clay underneath. I try to break through this and use gypsum in the hope that the overall drainage is improved. Otherwise the raised bed has to be used.
For frost sensitive species it pays to plant during spring to gain the growth and hardiness required before the first frosts in the following autumn.
Like all new plantings, the root ball of the plant needs to be kept moist until the roots have moved out into the surrounding soil. Always make sure that the drippers, if using them, flow onto the root ball. I have had most losses because of this failure.
Frost Tolerant Banksias
I thought I would research Banksia species which are suitable for areas where frost is an issue. Some species are frost tolerant once they are established.
Frost Tolerant Banksias
Species without any notation are known to be frost tolerant. Some species are not listed because I have not found reliable information about the frost tolerance.
Banksia aculeata (light to moderate frost)
Banksia ashbyi (tolerant when established)
Banksia attenuata (tolerant when established)
Banksia audax
Banksia baueri (woolly Banksia, Possum Banksia) (tolerant when established)
Banksia baxteri (Birds-nest Banksia) (tolerant when established)
Banksia blechnifolia (light to moderate frost)
Banksia brownii (when established)
Banksia burdettii (when established)
Banksia caleyi (when established)
Banksia candolleana
Banksia dentata
Banksia elderiana (Swordfish Banksia)
Banksia elegans
Banksia grandis (Bull Banksia)
Banksia hookerana (Acorn Banksia)
Banksia laevigata
Banksia lanata
Banksia lemanniana
Banksia leptophylla (tolerates light frost)
Banksia lindleyana (Porcupine Banksia)
Banksia lullfitzii
Banksia marginata (Silver Banksia)
Banksia media (Golden Stalk, Southern Plains Banksia)
Banksia meisneri (moderate frost tolerance)
Banksia menziesii (Firewood Banksia)
Banksia nutans (Nodding Banksia)
Banksia occidentalis (Red swamp Banksia) (Tolerates light frost)
Banksia oreophila
Banksia petiolaris
Banksia pilostylis
Banksia praemorsa (Cut Leaf Banksia)
Banksia prionotes (Acorn Banksia)
Banksia repens (Creeping Banksia)
Banksia robur (Swamp Banksia)
Banksia saxicola
Banksia scabrella (tolerates light frost)
Banksia sceptrum (Sceptre Banksia)
Banksia speciosa (Showy Banksia)
Banksia sphaerocarpa (Round -fruited Banksia)
Banksia tricuspis
Frost and Seaweed Products
Theoretically, the frost finishes tomorrow until the next bout! Another beauty today had me trying twice to get out of our driveway without the windscreen icing over.
Yet everything that I am growing is looking ok, amazingly. I must say that I have a ‘nasty suspicious nature’ when I read such things as ‘frost tolerant, drought tolerant, lime tolerant’ etc. Until I have the evidence for myself, I am always wary of other people’s assessment of these qualities. Unless I know the geography of the area where a species naturally grows! Or I know the climate of a particular nursery eg. one from an area of high frequency of frosts that come with very low temperatures.
I have read various claims about seaweed type products improving the frost tolerance of young plants. Having read it, I thought I would deliberately try the products, not only for their usefulness in settling in new transplants but for this quality as well. I cannot say that I have set up a very scientific system of measuring this. I am more interested from the point of view of a home gardener as well as a nursery grower so it will be purely anecdotal.
Frost Hardy Plants
This is the coldest winter we have had for a few years. Recently there have been 5 frosts in a row and this seems to be the pattern. Apart from 7.5mm last Friday there has been no rain so the potential for damage to plants is increasing as this dry weather continues.
It is a standing joke amongst Australian native plant growers that if it will survive in Canberra during the winter, it will survive anywhere. When we first moved here, the small publications published by the National Botanic Gardens were a bench mark for frost hardy plants.
Many more plant species have been available since these books were first published (from 1971), so the original list is quite small in comparison with what is known today.
The plants listed in Volume 1 are as follows:
Banksia ericifolia (Heath leaved Banksia)
Banksia marginata (Silver Banksia)
Banksia spinulosa (Hairpin Banksia)
Banksia serrata (Saw Banksia)
Banksia integrifolia (Coastal Banksia)
Banksia media
Banksia robur
Banksia baxteri
Eriostemon myoporoides (now Philotheca myoporoides) Long-leaved Wax Flower
Melaleuca wilsonnii (Wilson’s Honey Myrtle)
Isopogon anemonifolius (Drumsticks)
Goodia lotifolia (Golden Tip)
Acacia drummondii (Drummond’s Wattle) -needs protection from frost until about a metre tall.
Indigofera australis (Austral Indigo)
Grevillea baueri
Hypocalymma angustifolium (Pink-flowered Myrtle)
Boronia heterophylla
Melaleuca incana (Grey Honey Myrtle)
Micromyrtus ciliata (Fringed Heath Myrtle)
Westringea fruticosa (Coastal Rosemary
Thryptomene calycina (Grampians Heath Myrtle)
I will add to this list later and find more cultivation information.