Proteaceae

Plants in the Proteaceae family are incredibly old. Researchers know that their origins are more than 140 million years old. That is when Gondwana started to break apart. Gondwana was the super continent that existed in the southern hemisphere. Fragments of it are Africa, South America, Australia, New Zealand, Antarctica, India and a few other bits and pieces that got flung to the far corners of the globe.

If you are interested in how the southern hemisphere was crafted from Gondwana, check out this animation. Amazing!

Gondwana

The above animation (uploaded 2020 April 6) demonstrates the central role of the Bouvet mantle plume in the break-up of Gondwana and the dispersal of its constituent continents using model CR20ABBK.  Some explanation of the colors is given in the blue text below. Higher resolution JPGs of the frames making up the animation are available [here].  Explanatory notes are in preparation.  Specific queries are welcomed meanwhile. Colin Reeves. 2020 April 14.

Plants from the Proteaceae family exist on most of the fragments of Gondwana, although they have since evolved separately and each piece of Gondwana has undergone climate change causing their evolution to be quite different. I suspect that they will find fossil evidence in Antarctica at some point because some of the species clearly migrated across this land mass to end up where they are today. Fossil records show many species were once prevalent in places like New Zealand which are now devoid of them – another indicator that as the land masses moved, the climate or environmental conditions changed and they were unable to adapt.

Plant Distribution

I am going to spare you all of the botanical details, the arguments over classification (which continue to this day) and just stick to what I think is interesting. The family was named in 1735 by Carolus Linnaeus after the Greek God Proteus, who could change his form at will. This supposedly reflects the highly differentiated forms that Proteas have. Give or take a few, there are 83 genera with more than 1600 known species in the family.

Most of them can be found in Australia, which counts around 45 genera (35 of them endemic) with 850 species, South Africa that counts 14 genera (11 endemic) with 400 species, South America counts 8 genera (4 endemic) with about 90 species, New Caledonia has 9 genera (6 endemic), Eastern Malaysia and New Guinea together have 8 genera (none endemic). Almost all of the Proteas in Africa are contained within a very small area of South Africa called the Cape Floral Kingdom, between Nieuwoudtville in the northwest and Grahamstown in the east.

There are two primary divisions in the family – the Proteoideae, which are widely spread and the Grevilleoideae which are principally in Australia. This is a graph of the major family tree, put here as much for my own reference as anything else.

Proteaceae Family Tree
Proteaceae Family Tree

Proteoid Roots

There are a few things that are notable about the family as a whole. The first is that they have a very specialized root structure – which are called proteoid roots. These are lateral roots that spread just below the surface and only exist seasonally, shriveling at the end of each growth season. Proteoid roots are necessary for them to get the nutrients they need from what are very impoverished soils in their native regions.

Proteoid roots
Proteoid roots

Phosphorus-deficient soils and scarce water make it difficult for these plants to extract the necessary nutrients. They do it by exuding carboxylates that mobilize phosphorus tied into other compounds. As a result, if you feed these plants with a regular fertilizer, you will kill them, just like taking an overdose of drugs. You never give these plans a fertilizer contain phosphorous. That is the middle number in a fertilizer – so if you give them a balanced 10-10-10 fertilizer, your plant will probably die.

These roots are performing a similar function to the mycorrhizal fungi symbiosis that happens with many plants. These fungi dissolve nutrients from the soil and make it available to the plants in a liquid form that can be taken up by the roots. Mycorrhizae also protect the plants from other soil born organisms, such Phytophthora. If you have ever seen a plant that one moment looked healthy and then the next day is wilting even though the soil is moist – it is probably Phytophthora or water mold. Without the mycorrhizae, Proteas are vulnerable and so must be given very good drainage.

Flower Form

When you first look at the plants that make up the Proteaceae family, you will see a stunning array of flowers. Some of them are huge flower heads, other are like a bottlebrush, some are very spindly, like a spider and other form long strands. In each case, the flower head is actually an array of very small flowers. The Banksia may have 3000 individual blossoms in one flower head! Each flower opens in a progression, often making making the flower head appear to go through several different stages. Many of them also deploy large colorful bracts to add to the floral display.

Growth Cycle

In the US, the growth cycle for plants is to be dormant in winter, rapid growth in Spring, bloom in Summer, and harden off and set fruit in Autumn. For Proteaceae, it is reversed. Autumn is the rapid growth season, they flower over Winter and early Spring, then set fruit and harden off before Summer. This is because Summer is the toughest season for them – lack of water and extreme heat. That makes these plants a very welcome addition to the garden because they are winter/spring bloomers and some of the Grevillea continue to bloom year round here.

This may present a problem for us in Oregon, because the lack of heat has not really been studied. More on that in a moment.

Regeneration Cycle

Many of these plants have a fairly short lifespan – some only about 8 years. Luckily many of them live a lot longer, especially since it takes four or five years to get them to bloom from seed. This is, in part, because of the harsh environment that they grow in.

Forest fires are very common and so they have protection methods to deal with that. Some of them have lignotubers that hide underground, and they can re-sprout from them after a fire has passed.

Others contain their seed in a very hard wood coating and only release the seed after intense heat. Many of them require the smoke from a fire to break their dormancy. When fires are to be expected every 10 or 20 years, there is no advantage to being a long lived plant.

Growing in Oregon

Very few people have tried growing Proteaceae in Oregon. In this country, they are restricted to California or Hawaii. Most of the US is either too cold or too humid. These plants want a Mediterranean climate, which is characterized by a wet, mild winter, followed by a dry hot summer. In addition, they tend to want very well draining soils.

In Oceanside, Oregon, we are basically built on sand, so drainage is as good as it gets, and our soils are very impoverished. That means we will not damage their root structures.

We are in USDA climate zone 9b or possibly even 10a – the same as Hawaii and California. There has not been a frost since we moved here 5 winters ago. Our summers are dry, often going two or more months without a drop of rain.

What we don’t have is heat in summer. Very few people have written about the impact that a lack of heat has on these plants. There are a few nurseries in the area that do offer Grevilleas for sale and we have successfully grown them and brought them into bloom. We do not yet know if we will be able to get some of the others to bloom and if other plants, such as the Banksia, Leucospermum and Protea will flower here. There are a few pieces of evidence that places in Washington have managed to get some of them to bloom. This is an experiment.

2021 Update: This year we have had Leucospermum, Leucadendron, and Protea blooming and a Banksia is getting ready to flower. At this point, I think it is safe to say that they grow quite well in Oceanside, Oregon.

Major Categories

The plants within this group that interest me the most are Banksia, Grevillea, Hakea, Leucadendron, Leucaspermum, Mimetes, Protea, Serruria, and Telopea. The other notable genus is Macadamia, but these are way to large for me to be growing.

I highly recommend the book Protea: A guide to cultivated species and varieties by Lewis J. Matthews. It provides a good overview of the major plants in this family and has some great pictures. The biggest problem is that it will make you fall in love with plants that you cannot obtain easily.

Recommended Products

Pronunciation: pro-tee-AY-see-ay

Name Derivation: Named after the Greek God Proteus, who could change his form at will.

In The Garden

Grevillea
Protea
Banksia
Dryandra
Leucadendron
Leucospermum
Adenanthos
Isopogon
Hakea
Mimetes

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