Mountain Cabbage Tree

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Amazing that "cabbage tree" is the common name of this sensational African species.  Yes, the leaves can be cabbage blue, but given how much they look like the snow-flakes we all cut out of folded paper in elementary school, wouldn't "snowflake tree" or even "doily tree" be better?  This picture shows the tree later in the Summer, when canes of a yellow-leaved ghost bramble, Rubus cockburnianus 'Aureus', had scrambled up through it. 

 

Earlier in the season, you can see the leaves' long stalks more readily without the vibrant distraction of the Rubus.  This is my second try with Cussonia; I overwatered the first in the Winter when it would have preferred to stay dormant.  This new one is a fast-growing youngster: two feet over the course of the Summer.  (See "How to handle it" for strategies–and there are a few—to enhance various aspects of the plant's foliage and growth.) 

 

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Newly-formed leaves will be even bluer than these when the plant receives less water; see "How to handle it" for strategies to encourage bluer leaves.  Over this first Summer, though, I'm encouraging height instead of blueness, so I've watered the plant generously.

 

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Look below to see how widely-spaced the leaves are on the young stalk:  This plant is growing quickly. 

 

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In a few years, my Cussonia should be as tall as I am, with the foliage all at the top of the trunk.  The plant will look like an exotic palm tree, and I will have to be a stepladder to take the shot below, looking down on one of the incredible leaves.

 

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Yes, the foliage color is blue, but its geometry is even more amazing: I'm definitely going to start calling this my doily tree.

 

 

 

Here's how to grow this unique tree:


Latin Name

Cussonia paniculata ssp. sinuata

Common Name

Mountain Cabbage Tree

Family

Araliaceae, the Ivy family.

What kind of plant is it

Evergreen subtropical tree.

Hardiness

Zones 9 - 11

Habit

Often single-trunked for the life of the plant, with a dense cluster of large and (depending on how the plant is grown) exceptionally colorful foliage only at the top, as if the plant were being tutored by coconut palms.  Older plants sometimes bifurcate high up the trunk, forming two equal "tributary" trunks, each with its own palm-like crown of foliage.   While not particularly thick, the trunk has very corky bark with characteristic deep vertical fissures. 

Rate of Growth

Fast when young and when it gets plenty of water; slow in its native low-rainfall habitats.

Size in ten years

In native climates—hot, semi-arid, and virtually frost-free—perhaps eight to ten feet tall and only four feet wide.  In containers overwintered in colder climates, but with richer soil and more water, almost as tall.  Ultimately to about fifteen feet, only sometimes branched.

Texture

The foliage itself (see below) is exceptionally lacy and doily-like.  Cussonia prefers to keep the foliage atop an unbranched trunk, though, so overall the plant's look is that of a uniquely-foliaged standard, a specimen lollipop. 

Grown for

The foliage!  Cussonia leaves are extraordinary across many metrics:  Overall size, complexity and delicacy in the shape even at that size, coloring, spacing up the stem, and radial array around the stem.  The leaves are round, but so intricately lobed and dissected that they look like doilies.  They're held on long stems and crowd the top of the plant's single or, at the most, few trunks.  Leaf color can be varied by changing the growing conditions, from slate green to a strong blue-grey or even a powdery aluminum; see "How to Handle It" for strategies.  New foliage can vary in color, as well; ideally it's a shiny and bright burgundy-red.

 

Its habit: Put that remarkable foliage atop a narrow and (usually) unbranched trunk, and you've got a plant that looks more like a palm tree.

 

Its rugged suitability for dry climates.  Native to South Africa, Cussonia tolerates hot and low-water conditions (think unirrigated portions of your garden in California, even the extra-hot "hell strips" between the sidewalk and the street, or parking-lot islands).  It also succeeds long-term in containers. 

Flowering season

In Winter into Spring:  January to April.  The flowers are small and green, but in dense and upward branching spikes that are striking rather than pretty.

Culture

Full sun and excellent drainage.  If growing in-ground, no water in Summer after it's established.  If Winter is cool enough to induce dormancy—into the 30's or even the 40's—be careful that the plant doesn't get too much water then, either.

How to handle it

Intriguingly and sometimes frustratingly, the same handling doesn't bring result in uniform improvement in the cabbage tree's diverse and appealing characteristics: Overall size, leaf size, mature leaf color, juvenile leaf color, and speed of growth.  Frustratingly, speedier advance on some fronts only brings a retreat or even a collapse on others.

 

Basically, plants with the plushest life—the biggest containers, the richest soil, the most plentiful water—grow the fastest and produce the largest leaves.  Growth can be so fast, especially when the plants are young, that Cussonia can be used as an (expensive) annual to bring unique as well as heat- and sun-proof foliage to Summer containers.

 

For plants that are kept year to year as an overwintered "conservatory" specimen, this quick growth can be desirable for the first year or two:  Cussonia quickly "trunks up", or rather trunks upward, getting surprisingly tall even in small containers, in which case it loses lower leaves almost as quickly as it grows fresh new ones at the ever-heightening top.  Even young plants soon look a lot like a papaya with unusually lacy leaves, or even, at first glance, a newly-discovered form of palmate-fronded palm.  Both of which would be high praise, indeed.  Because Cussonia isn't the plant to pinch for a more-branchy look, and has the potential to get taller than a normal-height room, containered plants are best grown on the dry side after they're two or three years old, to keep their upward growth as slow as possible.

 

Woe unto anyone who doesn't severely cut back on watering over the Winter, especially if the Cussonia has been recently potted up and there aren't all that many roots to absorb water from the soil and dry it out:  The tree's trunk is, itself, a water-storage device, and young plants often have a swollen caudex-like base, too, which is also a water-storage tactic.  In other words, the tree is expecting some drought, and often can't handle not getting it.  If there's too much moisture in the soil when the plant is otherwise dormant because of cool temperatures and shorter winter days, rotting is a serious danger.  I speak from painful experience. 

 

Pot up your Cussonia, then, only in Spring, so the roots can get a complete grip on the new soil by Fall.  And unless you overwinter in a warm greenhouse, withhold water entirely except when the plant is clearly letting you know it would appreciate a drink:  Drooping lower foliage, a trunk that's gotten more wrinkled because its moisture has been used up to keep the foliage hydrated, and—the best sign of all—eager new growth.  Resist the urge to be nice and give the plant regular water in a fit of potentially lethal generosity.


If you've been able to steward your Cussonia through its first few Winters, you've mastered keeping its water needs low enough if the plant slows down in cooler weather.  If you're growing the plant in climates more similar to its native South Africa—coastal California, say—your "Winter" might be mild and rainy enough to provide Cussonia with the weather it needs for its most active growth.

Downsides

The foliage is so distinctive, as is the plant's overall palm-tree habit, that there's no way for this plant to be anything but a star of your garden.  If you don't have a suitably focal location to grow Cussonia in-ground, keep it in a container. 

Variants

Cussonia are a small genus—about twenty species—whose differences one to the next are only truly rivetting to fellow Cussonia nuts.  In addition to C. paniculata, the "mountain" cabbage tree, there are "forest," "rock," and "coast" cabbage-trees, too.  Plus an even more silver-leaved "grey" species.  And, as I say, about fifteen others.  I don't believe that any is hardier than Zone 9, so for most of us, these are plants for containers. 

Availability

On-line and, where Cussonia is hardy in-ground, at retailers.

Propagation

By seed. 

Native habitat

Cussonia paniculata is native to South Africa.

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