You might try adding some lime to your potting mix. Many WA Banksias are lime tolerant and it is said to suppress soil fungi to which WA Banksias are susceptible.

I have some Banksia ashbyii growing in pots and the soil mixture contains quite a lot of garden lime. All the 3 are positively booming so far.

It's hard to believe that any British climate could be similar to South-west W.Aust, which has a classic Mediterranean climate - wet summers, dry winters.
I don't know about the South-east. Have never been there, but I believe it's arid. Here in SE Qld we have a problem with some of the WA Banksias resenting the humidity and getting fungal diseases. They do much better west of the Dividing range where the air is drier and the soil more alkaline. Good drainage is crucial, root disturbance is deadly, and over-watering is not good for the ones you have. Our Eastern Australian Banksia robur is a lovely thing, and does much better in the damp - though here it's damp and humid in summer and they prefer to be drier in winter.
I had always imagined that the British could get good advice on growing that sort of thing from Kew? A certain Sir Joseph was of course influential in introducing Banksias to England, though they were from coastal Eastern Australia, not the lovely things from the west. Growing foreign plants from extremely different climates is something the English are particularly famous for in the field of gardening, so you might find better advice for growing them in your particular conditions over there, rather than here.
Best of luck!
Trish

Banksias grow prolifically in Tasmania where we enjoy about 8 frosts a year. They are very tolerant of the salt winds where we live. Not sure of the varieties but I'm heading for our native nursery on Sunday next for advice on Aussie natives to plant as windbreaks so will ask about the species you have. Will get back to you. They really seem to grow in all soils - we have heavy clay, but the next settlement aptly called Banksia Park varies from rock to sand and there is a forst of them there. We don;t get down to -5 often but it does happen that we get 0 overnight in winter and in Hobart south of us, they grow on Mt Wellington which frequently would get - temperatures.

Hi,
Banksia canei is from the east so would prefer slightly acid soils. It will tolerate frosts happily when bigger. I'd plant both in mounded sites when bigger, but keep them in gradually increasing pots until maybe 20cm tall.
Not sure about coccinea and alkalinity - neutral?

Cas

Congrats if you still have your Banksia coccinea seedlings. Book by Wrigley and Fagg says that these are hardy to frosts of -7C in conditions of normal rainfall (as opposed to frost in drought conditions which can be devastating.) They grow in slightly acid sand over limestone in the SE of South Australia. Main consideration is always good drainage and go by the colour of the leaves for nutrition. If the veins are prominent or leaves pale, look for slow release fertiliser and use at half recommended strength.

I have managed to get some of the Australian plants I have grown from seed to 6 or 7 inches in height. I have several silver wattle, red gum and (I think) peppermint gum. The first question I have is, can someone please recommend a good book for identifying Australian native plants. I live on a limestone ridge with very shallow soil, although if I manage to get plants established they thrive. The weather goes froma freezing -8 degrees in the winter to long, hot, scorching summers (32 degrees today), so the second question is can I successfuly grow Australian natives in this climate and if so are there any plants in particular that I should try? I have a daughter living in Perth and I fell in love with all the wonderful plants I saw growing there and would like to make a small corner of France into an Australian garden, so would be grateful for any help you can give me.

None of those plants will be thrilled with -8C, but they'll live happily to at least 45C (the hottest I can remember in Melbourne).

I would try Euc. pauciflora, Euc. nivia, Euc. delegatensis. Red gum(Euc. camaldulensis) would probably do ok if it is a desert variety.

Not much from round perth would like freezing I think. You can probably get lechenaultia biloba in Europe, a classic WA plant.

Banksias from Western Australia look great but have their problems. It is likely to be easier to grow Banksia spinulosa from eastern Australia. They will survive in your climate and are tough plants so long as they are well drained. There are yellow, red and black forms - I can provide photos and seed on request.

I have been growing Banksias in Vienne (near Lyon) France for 5 or 6 years now. I have some B coccinea seedlings myself, but this species has a reputation of being difficult. In WA, it grows in deep sand dunes near Albany, so use extremely well draining substrate. Secondly, my general experience with other banksia species (I have about 30 different, of which 5 have flowered) is that Banksias, do not like too much lime: I have very hard mains water here (equivalent of 280g of CaCO3 per cubic metre) and my early attempts at Banksia cultivation resulted in extreme chlorosis and death due to the pH rising. I have had much more success since I have taken steps to keep the pH down (I aim for pH 5). I even saved a chlorosed B blechnifolia by dunking it in a weak solution of Nitric Acid!! Even with these precautions some (not all) of my B coccinea seedlings are looking yellow, so I recently gave a dose of chelated iron. Thirdly all WA Banksias detest humidity, so do everything you can to reduce humidity in your greenhouse (fan, etc) and water sparingly especially in winter. Finally Banksias do not like phosphate, so do not use any fertilisers other than extremely low phosphate ones.

Banksia canei grows in the Blue Mountains on the other side of Australia and is one of the toughest Banksias as far as cold and frost is concerned, so could be planted outside if you never get much lower than minus 5°C. I have also found that it is also more lime/pH tolerant than most banksias. More generally, as far as frost resistance goes, Australian climates are so different from Western European climates that only information gleaned from those who have tried growing Banksias in Europe is likely to be reliable. I have three 5 year old B canei and they are yet to flower. If you are seriously into growing Banksias and other Australian plants may I suggest you join the (UK) Australasian Plant Society? I would be please supply their address.