How to grow Proteas
The main consideration to take into account is that they must have a very free draining poor acidic soil. If you feed them with phosphates you will probably kill them.
"Hardy varieties"
Although none are truly hardy if you can provide good drainage then the following are well worth trying:- with many being hardy down to minus 5 - 10 degrees. Those marked with a * are the hardiest.
Banksia integrifolia
Banksia marginata
Leucadendron fireglow *
Leucadendron Early yellow*
Leucadendron Safari Sunset*
Protea eximia *
Protea cynaroides
Protea repens*
Protea subvestita*
Protea grandiceps*
Wind tolerance
Many varieties of Protea grow near the coast in their natural habitat. However by planting in a coastal situation the growth habit can be altered significantly. Also they prefer shelter from very cold winds. For a windy situation, particularly near the coast the best varieties to choose are:-
Banksia marginata
Banksia integrifolia
Hakea - some
Protea cynaroides
Protea neriifolia
Protea repens
Protea grandiceps
Leucadendron argenteum
Leucadendron laureolum
Leucadendron salignum
Soil Preparation
Basically the golden rule is to make sure that the soil is prepared properly. As I said earlier drainage really is the key. On heavier soils it is probably advisable to consider a raised bed system. Add plenty of coarse grit and composted bark to the planting holes. If the soil is on the alkaline side add lots of pine needles if you can get hold of them as this will help with the drainage and also increase the acidity. Be wary of adding anything with fertilizer in. (See below)
Fertilizing
Very difficult to advise here as every situation is different. The basic guide is that for any Protea grown in the ground there is probably already enough nutrients and adding any more will just not be necessary. In containers it is a little more complicated. In my own experience I have found that the best approach seems to be to using a mix made up of;-
Bark chips, Peat, a little garden soil (less than 10%) and grit, making sure to use plenty of crocks or polystyrene in the bottom of the pot. The only feeding that will be needed is to use fertilizers VERY low in phosphates. These can be difficult to source but your local nursery or garden cente should be able to help. It pays to keep an eye out for leaf yellowing which may be caused by a lack of iron. If this is the case a dilute solution of cheleated iron should solve the problem.(Sequestrene)
Pruning
A relatively easy process but it does vary according to variety. Those with a lignotuber (an underground trunk) such as P. cynaroides can be cut back very hard to 5cms above ground. This will encourage strong shoots to form which will usually flower in about 18 months. For detailed advise on pruning and many other aspects of growing this very rewarding family of plants there is a very useful book called Growing Proteas by Rob McLennan ISBN 0-86417-499-3 I think Amazon.co.uk stock it. Or alternatively call Trevena Cross Nurseries on 01736 763880