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Growing Proteas in California

Protea Atlas LogoDavid Bowkster writes:

I have questions regarding how to successfully raise proteas. I live in southern California which should be similar climate-wise to South Africa, where these plants grow wild.

I've owned perhaps a half dozen of different varieties and have killed every one eventually. I can't figure out what I'm doing wrong and local nurseries don't seem to have the expertise. I've read a few texts regarding their care, for example: proteas

  • like breezy spots...

Yes, but unless the humidity is high this is not a major problem. If you water onto their leaves it is crucial to have wind. So irrigate by means other than overhead sprinkler. Otherwise, in a mediterranean summer (hot and dry) you should have no problem. If your plants are small and hidden within larger plants then you may have a problem with overheating until the plants grow up to the same height as other plants. Sufficient water should help this.

  • they don't like any other plants to interfere with their root growth..

This is nonsense. Proteas grow naturally in veld with up to 60 other species within their rooting radius. So long as your density of proteas is not too high, other species (preferably smaller - e.g. Ericas, Restios, Rutaceae, daisies, and so forth) can happily be grown with them. Lawns are bad news, but primarily because of fertilizers, although they do interfere with the feeding roots.

However, what proteas do not like at all, is disturbance to the root system. No tillage or weed removal or hoeing. This kills the surface feeding roots and increases infection.

  • need sun..

For most species full sun is required.

  • good drainage...

For most species a deep sandy soil. Otherwise a well-draining loamy soil.

  • don't like fertilizer...etc.

Fertilizer is fine. Provided that it is acidic (not alkaline - so ammonium based, not nitrates or nitrites), and most importantly provided it does not contain ANY potassium or phosphorous. Bonemeal is instant death. Manure is slow death. Only acid mulches should be used, but with care as they introduce pathogens. Nutrient uptake is via specialized feeding roots (proteoid roots) which are super efficient at taking up trace amounts of nutrients. Overfertilizing results in lethal quantities of nutrients being absorbed. Plants to be fertilized (e.g. for commercial picking of large quantities of flowerheads) should be regularly fertilized from planting to ensure that minimum amounts of feeding roots are produced.

I know others here who succeed and one person who has a huge plant and does nothing.

This is the formula. No root disturbance, no fertlization, no damage to the plants. Remember, most proteas grow naturally on soil most agriculturists refer to as pure glass. It is very well drained, almost totally free of nutrients and regularly sterilized (every 15-30 years) by fire.

My experience is that my plants will live for a year or two, never really grow a lot and not really prosper, then die.

It sounds like an overfertilization problem. The plants germinate (or the cuttings come from a nursery) and then start putting out feeding roots and accumulating toxic levels of nutrients and slowly die of poisoning.

My questions:

  • do they prefer the soil to dry out between waterings?

Proteas are water thirsty. The first thing a protea does is grow its tap root. A two month old protea seedling with two leaves and standing less than 5cm high can have a 2m deep tap root. Surface roots are for feeding and are ephemeral - based on season and moisture availability. Proteas do not shut down during the dry season like most other Fynbos plants, they use the deep water to continue growing. Most of your watering will only help the feeding roots. Unless you are commercially growing proteas, watering is only needed in the two years to establishment. Thereafter, watering is not essential, except during spells of exceptionally dry weather. Make sure water is acidic to neutral without any salts. Hard water will result in slow death (due to accumulation of toxic levels of nutrients).

The above assumes that you have a water table at between 2m and 15m below the soil. If not (e.g. desert regions) you will have to water - preferably with a drip and preferably so that water will go deep.

  • Do they like full sun or partial shade?

Most species prefer full sun. In the shade they grow leggy and etiolated and turn yellow and die. None can grow in deep shade or even in the shade of a deciduous tree.

  • What is the single most important thing to ensure...good drainage,

Two more issues about drainage and watering

  • Proteas do not like being waterlogged. If the plants are watered make sure that the water drains away (down!) and does not stand for more than a few minutes. If it does you have a drainage problem. If you are watering with a drip, make sure that the winter rains are sufficient to eliminate any concentration of nutrients around the plants as drips in arid areas are prone to do. Be careful of making sandy pits in clay soil where the water sits and cannot drain away.
  • Beware of infection by water-borne diseases. The worst of these is Phytophthora root rot. From infected material (other plants, soil from nurseries, from mulch) the fungal spores are dispersed by water and infect roots. This results in dieback of the root system. This is not noticed until the plant requires water. So the plant will appear normal until one hot day. Death will occur within hours, unless you notice it early and prune and water. If you have the fungus and notice that your plants are dying like dominoes during the summer hot weather you will need to sterilize your soil or plant Phytophthora-resistant species or use Phytophthora-resistant root stock and graft your plants on them. Be aware that hoeing spreads fungus quite efficiently, as does flood watering and mulch.
  • never letting the soil dry out,

Dealt with already - this is nonsense in most cases - but only if your plants are established. In the wild proteas all grow up together (with other plants) after a fire. In mature veld no seedlings survive (some live until summer) because of the older plants taking all the water. In your garden, unless it is a new bed, you will have to water your plants until established (about 2 years). Also, in the wild the fire will have sterilized the seedbed. In your garden pathogens will be moving around. If you do feel the need to sterilize the soil before planting, make sure that the fungicide does not have any copper, potassium or phosphorus.

  • isolation from encroaching plantlife...

This is rubbish. Proteas - especially the bigger ones - prefer to be top dog. But they tolerate lots of smaller plants around them. Lawns are a problem, but primarily because of watering (especially sprinklers) and fertilization.

  • can they grow in containers...

Yes. they grow well in containers. In which case use a sandy soil or very sandy loam. And definitely never allow to dry out (no water table for the tap root)! For more information look at Growing Proteas in Pots.

  • what kind of soil...

Any kind of soil provided that it is well drained and free of toxic nutrients.

Sand and glass are best. Sandy loams are good. Clays and silts are almost impossible. Acid pH is by far the most important aspect.

  • what kind of care eg do they appreciate being cut back or flowers left on the plant to fade???

Treat them like any other plant, except remember that unless there is a green leaf there is not leaf bud. So if you cut into wood that has no green leaves you will kill that stem. Cut flowerheads after flowering if you want to get more growth (before the plants allocate resources to them, the seeds are packed with nutrients, but this is only done several months after flowering, so there is no hurry). Leave them on the plant if you want seeds. This is aesthetics and when it comes to pruning, proteas are like most plants - they benefit from some "training and shaping".

Any suggestions would be appreciated as I really admire these plants,

  • Remember that there are exceptions to these rules. Thus:
  • Resprouters must be cut to the base, ignore the green leaf rule. Have a look at Garden Tips and Resprouting.
  • There are species that tolerate rich soils (but there are not many, and they are not the best) and alkaline soils. In fact the proteas that grow on limestones grow well on any soil (those growing on sands are most intolerant of other soil types). Have a look at Matching Proteas to Your Garden.

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