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Re: Proteaceous plants in clay soils

[I tried to send this yesterday, but I believe it didn't get through -- the
UCDavis listserver doesn't seem to recognise me any more.  So I've
resubscribed and am trying again.  Please excuse me if it gets doubled up.
John]

At 02:10 PM 9/10/97 -3121, Wallace Gorell 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.'

Here on the east coast of Australia, many of the Western Australian banksias
(in particular, in my experience, B grandis) tend to be short-lived (a year
or two).  This is said to be due to be due to either or both the humid
summers and the root rot fungus Phytophthora cinnamoni.  Presumably the
first will not be a problem at Berkeley; I wouldn't know about the other.
(The same is true of many other WA Proteaceae, though not all -- many
Grevilleas do fine.)

Really good drainage is supposed to help.  I've heard that some enthusiasts
have tried an underlayer of crushed limestone (a few feet down) for some of
these difficult WA plants, with apparent success.

>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? 

Definitely worth a try.  Also you could try mounding up the bed a foot or two.

It's a pity that most of the banksias with really spectacular leaves fall
into this "difficult" class.  But if they don't work, you can always try
some of the east coast species.  B serrata (both tree and prostrate forms)
and B robur have interesting leaves and are easily grown in most soils.

The SGAP page on banksias is worth a visit, if you haven't been there
already. (http://www.ozemail.com.au:80/~sgap/banksia.html)

John
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