An Introduction to Protea Plants and Their Relatives

By Richard Flowers, ACCNP, Green Thumb Nursery, Ventura

There is a specialty plant group that is often overlooked and doesn’t get the attention it deserves. These plants belong to the family called Proteaceae, and they include Grevilleas, Protea, Leucospermum, and Leucadendron. This grouping encompasses some of the most fascinating, interesting, and durable plants around. They are hummingbird magnets and attract butterflies too. Protea plants range from ground covers, shrubs, and trees to even a fruit tree (the Macadamia). Their floral displays range from pincushions (Leucospermum) and cones (Leucadendron) to spidery or tubular structures (Grevillea). Most thrive on almost neglect, low water, low maintenance, and in fact, if you give them too rich a soil or fertilize them, in some cases they will not thrive. Welcome to the Proteaceae family.

These plants are native to South Africa and Australia and are fire-adapted chaparral plants in their native habitat, so you can think of them as our version of the chaparral you see in the hills (ANPSA). These Southern Hemisphere plants love our Mediterranean climate, because those drier regions of the world are much like Southern California.

Growing Proteas in Southern California

They are forgiving, tough, and underrated, but to succeed with them, give them all-day sun and exceptionally well-draining, acidic soil, with little summer water once they are established in open ground. Do not over water! The number-one thing that kills these plants is too much water, which invites Phytophthora root and crown rot. For best results, plant on a slope or mound the soil so the plant sits above grade for good drainage and air flow (UC Master Gardeners). Never water at the crown; irrigate out where the branches and leaves come off the plant. Until they are established, water every 3 to 4 weeks, deeply and slowly; in the coldest coastal areas, give no summer water at all. When you plant, use a cactus mix for sharp drainage, the more drainage the better, and give each plant plenty of room and air circulation so they aren’t crowded against each other.

Frost and Climate

Proteas grow well in coastal or cool inland areas, but keep them away from freezing temperatures. They are only moderately frost hardy, damage can occur around 25 degrees F, and younger plants are more tender, so protect them with frost cloth in a cold snap (UC Master Gardeners). Shelter them from hot, drying winds. If you grow them in containers, keep the pot partially shaded to keep the roots cool, and water early in the morning so the foliage dries before the cool evening, which helps prevent leaf and stem fungi.

Why Proteas Hate Phosphorus

This is the single most important thing to know about the whole family. Many Proteaceae have specialized proteoid (cluster) roots, dense masses of fine rootlets and hairs that form in the top layer of soil and release organic acids (carboxylates) to pry scarce phosphorus out of poor ground (Shane & Lambers, 2004). They evolved on ancient, phosphorus-starved soils, and that same super-efficient root system is exactly why ordinary fertilizer is dangerous: proteas take up phosphorus so readily that normal garden levels become toxic. Never apply phosphorus, and that includes bone meal, which is high in phosphorus and can kill members of the protea family (WSU Extension). Phosphorus toxicity shows up first as yellowing foliage, progresses to blackened leaves, and can eventually kill the plant.

In most California soils these plants need little or no feeding. If you do feed, use a low-phosphorus fertilizer formulated for native plants, the middle number (P) on the label should be low or zero (ABC Gardening Australia). Most will benefit from iron instead: a foliar spray of iron chelate, or soil sulphur to acidify the soil, corrects the yellowing that alkaline soil causes. Cottonseed meal is another gentle, acidifying option. One tip from experience: the proteoid roots are delicate, so when you plant, slide the pot off the root ball and set the plant in the hole gently, without disturbing or touching the roots.

Using Proteas in the Landscape

These plants earn their place in the garden. Many, if not all, do well in containers. Depending on the type, they work as screens, focal points, specimen plantings, hedges, formal plantings, ground covers, or accent plants, and their flowers and foliage are prized for arrangements. One of the best features is their long blooming period, and all of them are irresistible to hummingbirds, which feed gluttonously on the nectar. They pair beautifully with cactus and succulents in a drought-tolerant Mediterranean garden. Below are the main groups you will meet.

Grevillea (Spider Flower)

Grevilleas are mostly native to Australia and are a wonderfully diverse group, ground covers, evergreen shrubs, and stately trees. They are commonly called Spider Flower for their intricate, spidery blooms, and some are sweetly fragrant. Needle-leaved types add texture next to big-leaved tropicals; broad-leaved types suit any bed. Use larger tree forms for shade or a windbreak, shrubby types as hedges and privacy screens, and compact types in large containers on a deck, patio, or driveway. Foliage ranges from yellow-green to dark green, and blooms come in white, pink, yellow, and orange.

Leucadendron (Cone-bush)

Leucadendrons are called cone-bushes for their woody, cone-like seed heads. Their true flowers are quite small; the showy part is the brightly colored bracts (modified leaves) that appear mostly in winter. Native to South Africa, they are valued for durable, often rich-green or reddish summer foliage and neat, almost formal habits. They are dioecious, with male and female flowers on separate plants. All make excellent, long-lasting cut flowers, and many are grown for their decorative cones and foliage too.

Leucospermum (Pincushion)

The Leucospermum, or pincushion, genus has about 50 species, most native to South Africa, where they grow on mountain slopes, scrubland, and in forests. Depending on the variety, they range from low groundcovers to small trees, with long, slender tubular flowers massed on a thistle-like head. Pincushions are among the easiest proteas for beginners, tough, drought-tolerant, and happy in poor, well-drained soil (UC Master Gardeners of San Diego).

Protea (The Sugar Bush)

It would be a shame to leave out the crowning jewel the family is named for, the Protea. Linnaeus named the genus after the Greek god Proteus, who could change his shape at will; from that, the French botanist Jussieu derived the family name Proteaceae. Proteas carry tubular flowers in tight clusters surrounded by brightly colored bracts, and most are grown for the cut-flower trade. The king protea (Protea cynaroides) is the national flower of South Africa and a signature plant of the Cape Floristic Region’s fynbos (SANBI). Proteas belong to one of the oldest flowering-plant families on Earth: Proteaceae pollen fossils date to the Late Cretaceous, roughly 75 to 90 million years ago, when the family’s ancestors grew across the ancient supercontinent Gondwana (Missouri Botanical Garden). They are also nicknamed sugar bushes for their copious nectar, and the protea has come to symbolize diversity, transformation, longevity, and courage.

Green Thumb carries a range of these rugged, unusual plants that fit beautifully into a drought-tolerant Mediterranean garden, try pairing them with cactus and succulents, or with our other Mediterranean and drought-tolerant outdoor plants. Availability changes regularly, so please call ahead for specifics. And if a protea ever starts to struggle from wet feet or overfeeding, our guide on how to revive a dying plant can help.

Sources:

• ANPSA
• Phytophthora root and crown rot
• UC Master Gardeners
• Shane & Lambers, 2004
• WSU Extension
• ABC Gardening Australia
• UC Master Gardeners of San Diego
• SANBI
• Missouri Botanical Garden

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Protea & Proteaceae FAQs

What is the Proteaceae family, and what is its common name?

Proteaceae is an ancient family of flowering plants, commonly called simply the protea family, that includes proteas, grevilleas, banksias, leucadendrons (cone-bushes), leucospermums (pincushions), and macadamias. Its members share showy, nectar-rich flower heads and a strong dislike of phosphorus-rich fertilizer.

Where are proteas native to?

Most Proteaceae come from the Southern Hemisphere, especially South Africa’s Cape region (true proteas, pincushions, cone-bushes) and Australia (grevilleas, banksias). They evolved on ancient, nutrient-poor Gondwanan soils, which is why they thrive in lean, sharply drained ground and resent added phosphorus.

Can you fertilize proteas?

Barely, and carefully. Proteas and their relatives need little or no fertilizer, and they are highly sensitive to phosphorus, never use bone meal or a high-phosphorus bloom fertilizer, which can kill them. If you feed at all, use a low- or no-phosphorus fertilizer made for native plants (the middle number on the label should be low or zero).

Why are my protea’s leaves turning yellow or black?

Yellowing that progresses to blackened leaves is the classic sign of phosphorus toxicity, stop using any phosphorus fertilizer immediately. Yellowing alone can also be iron chlorosis from alkaline soil, which you treat with an iron-chelate foliar spray or soil sulphur rather than more fertilizer.

How cold-hardy are proteas?

Most are only moderately frost hardy, with damage starting around 25 degrees F, and young plants are more tender. In Southern California they are fine in most coastal and inland gardens, but cover them with frost cloth during a hard freeze.

How often should you water an established protea?

Sparingly. Once established, most proteas need only an occasional deep, slow soak every few weeks in summer, in the coolest coastal areas, none at all. Overwatering is the number-one killer, so let the soil dry between waterings and never water right at the crown.

Which proteas are easiest for beginners?

Pincushions (Leucospermum), many Grevilleas, and Leucadendrons (cone-bushes) are the most forgiving, tough, drought-tolerant, and happy in poor, sharply drained soil with full sun.