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Re: Proteaceous plants in clay soils

robwally@ix.netcom.com wrote:
> 
> I'm planning a west-facing bed with a number of Banksias (Australian
> members of the Proteaceae): Banksia grandis, B. speciosa, B. spinulosa
> var. cunninghamii, and B. spinulosa 'All Gold.' I plan to include the
> South African plants Protea 'Pink Ice' and Berzelia langinosa as well as
> the Australian Chamelaucium uncinatum 'Purple Pride', a member of the
> Myrtaceae.
> I've been growing these plants in pots for a year or so, but want
> finally to get them into the ground. The problem is my soil is heavy
> clay, so I'm planning to do more than merely amend.
> I'm thinking I'll remove the top foot of soil entirely, to be replaced
> with a sandy loam mixture, and that I'll incorporate some of that mix
> into the subsoil before I put the new topsoil in place. Does that sound
> to you all as if it will work?
> I plan to give no phosphorous at all and to water only occasionally and
> deeply in summer. I'm in Sunset zone 17 (Berkeley, CA), USDA zone 9, I
> believe.
> Any advice will be appreciated.

Hi Wallace 

Your soil mix would be even better if you were to include some gravel.
Most Proteaceae are fanatics for good drainage.

 From that point of view I don't at all like the sound of your bed. Just
replacing your clay with  an area of suitable soil, especially if it is
on the flat, would almost certainly create a water sump.

To have any chance of success you will probably need to make a raised
bed. You could first improve the drainage over the area to some extent
by digging in gypsum and clay or gravel and then put your bed on top,
making it say 10" high and surrounding it with some sort of retaining
wall such as rock, concrete blocks  bricks or  timber.

 Hopefully  some water will be able to  drain down into the opened up
clay and the remainder will run out from the bottom of the wall. I don't
think you need to worry about your plants having enough depth for their
roots. These plants tend to have rather limited roots anyway which also
means if your site is at all windy they will need staking until
established. Even better is putting rocks round them to hold the roots
down.

You are quite right not to give phosphorus, which is poison to these
plants. Actually, you probably do not need to feed at all as they are
more likely to have a long life if the soil is very lean. If you like
you could give them just a little compost as a top dressing, but even
this is probably unnnecessary. I have a Protea Cynaroides which has been
growing in a nich in a rocky hillside for the last 35 years without any
feeding. The bush is immense, looks in the pink of health and produces
an average of fifty enormous flowers yearly. Although we can sometimes
get pretty dry summers it has also not received any watering apart from
its first three years.

Water as you suggest through early summer, as this will encourage good
growth,  but you should stop for the late summer and the whole of
autumn, however dry. This is a very dry period in their natural habitat
when they become virtually dormant and if watered then you are quite
likely to lose them. On the other hand most come from winter rainfall
areas and are quite happy to be wet at that time (Strange, eh?).

If you want any further help just ask

Moira
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata, New Zealand/Aotearoa ("Land of the Long White Cloud")
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