How to Successfully Grow the Proteaceae Family, The Plantbase Way
Graham Blunt, from Plantbase Nursery, with a masterclass on how to grow Proteas, Grevilleas, Banksias and more... - 11 May 2018
The family Proteaceae is a large family of flowering plants found largely in the Southern Hemisphere, with the greatest ranges being found in South Africa and Australia. There are 83 genera containing over 1600 species, a range expanded further by selections and named varieties selected for garden use. Some of the better known genera grown in gardens include Protea, Banksia, Grevillea and Leucadendron.
These exotic and striking plants have a reputation for being tender and difficult to grow and propagate, but by following a few simple steps, and by choosing the right varieties, there are many that can be grown successfully in the UK.
The following is how we breed and grow Protea, Banksia, Grevillea and many others. It works for us on our nursery based in East Sussex.
Raising from Seed
Virtually all our plants in this family are raised from seed, which we buy from various companies throughout the world. Many members of this family have seeds that are programmed, through special coatings, that are stimulated to germinate following forest or bush fires. A number of nurseries that propagate from seed use special smoke treatments to simulate this process. We have never used these treatment for the following reasons.
Fire comes and burns, the seed pod ripens and then falls into ash, this tells it 3 things. Firstly all its rivals are toast, secondly the ground has just been fertilised with bonfire ash and lastly all the little mices (which absolutely will love to woof down your seed) are either cooked or any that survive have no ground cover to protect from any passing hawks, eagles or pterodactyls...
We start sowing in mid-February, hardier stock early in the month, less hardy later in the month. They are all sown in the same compost they are grown on in (see below). At this point I always sprinkle a bit of Sulphate of Potash on the seeds to simulate ash, bonfire ash should do as well.
They like cool nights and warm days to germinate. This can take a while but germination should always be close to 100% (unless you have been visited by pesky mice!). Pot up once they are getting their first true leaves.
Banksia ericifolia var. macrantha
As we are off grid at the nursery we have none of those fancy mist benches, which is why we tend to propagate most of our stock from seed. However, for some of the Grevillea hybrids we do cuttings and do them as you would any normal woody plant (but do use the Protea soil mix described below)
As an aside some suitable shrubs can be sawn down the middle to make two plants or more, this goes for the Protea family as well, although not recommended for those with heart conditions...
In the past we have tried every combination of compost and mixes, you name; coir; peat free, clay, subsoil everything. The results were always the same, they would germinate, grow happily to about 2 inches high and then one by one keel over and die. A consistent 95% of all the seedlings would scorch and burn. The few survivors would grow on and reach successful careers in the gardening world.
In hindsight this seems to be the point that these plants develop their ‘Protoid' roots. For the technically minded these are little towns built for hunter-gatherer bacteria that go forth collecting nutrients from the surrounding poor soil (much more efficient than roots alone), so what was happening is that the plants were suddenly overdosing on food and nutrients, and any that got through of course became strapping lads and lasses. The resulting infant mortality rate would make a Victorian proud.
Obviously commercially this is no good. The solutio, we hit on was pure Irish moss peat mixed with about 10% fine perlite. Immediately the death rate switched to a mere 2 to 3%.
Please note that once past infancy the plants become more and more soil tolerant with age. So as a rule of thumb the older and more gnarled and wizened the plant purchased the better it will survive planting out (Airpots, which I will come to later, also enable younger planting).
The Protea family, almost without exception, like poor well drained soil with good air flow. So using the aforementioned peat/perlite mix we also grow all these chaps in Airpots (please feel free to Google if you are not familiar with these pots), they are pricey but boy do the Proteaceae grow well in them, faster and stronger.
As far as watering goes, we are in a hard water area and I always use tap water with no ill effects.
Apart from regular watering, because although extremely drought resistant in the ground, if the pot dries out it is generally curtains for your prized plant.
If in pots they barely need feeding and when we do, we use a seaweed based feed sparingly.
A nice sunny spot and good airflow is essential. We lose far more plants in the winter to rotting off than from cold.
As mentioned before, the older and tougher the plant, generally the better. As a rule of thumb an open sunny spot with a gentle breeze is best. They don’t mind moisture as long as it doesn’t sit on the roots, none of them like waterlogging, but sandy, well drained soils, whilst ideal, not essential. Clay soils or stony soils are fine, but whatever the soil it must be at worst neutral at best acidic; very few can tolerate lime.
In summary, choose your spot, dig a hole to fit, stick your plant in the hole. Water it a bit and leave it. No soil preparation is needed except to maybe worsen it!
Notable Plants and their Toughness
Small is up to 6’, medium to 15’ and tree size, well like a tree.
Banksia marginata: medium sized shrub hardy to about -12C and also lime tolerant
Isopogon anethifolius: small shrub hardy to at least -12C
Protea subvestita: medium size shrub easily -18C (from the Drakensberg) the picture on our leaflet is it.
Protea cynaroides: smallish shrub only to -6C but easy to flower
Protea grandiceps: small to -10C, nice shrub
Banksia integrifolia: it’s a tree but what a tree, hardy to -16C flowers when young and small
Banksia robur: small to -14C likes a dampish spot
Grevillea ‘Canberra Gem’: medium shrub hardy to -14C, easy hybrid and long flowering
Grevillea x semperflorens: medium also to around -14C below
Leucadendron eucalyptafolium: medium shrub to at least -14C, easy
Hakea sericea: medium shrub, hardy to -16C, another easy to grow
Banksia spinulosa var. collina: small shrub to -14C, floriferous
Telopea specississima: medium to big shrub, to -14C
Lomatia tinctorina: small, very hardy indeed having been planted out on the edge of our car park for years in heavy clay, fragrant
Graham Blunt owns and runs Plantbase Nursery, in East Sussex, specialising in exotic, unusual and rare plants, a good number of which are of which are not listed anywhere else in the UK.