Plant's a bloomin' marvel

The other week the Head Gardener and I were racing out to Brancepeth for a book launch and we drove past a couple of flowering shrubs in a small planting at a gateway on the other side of the Weraiti Hill.

"What on earth is that?" she asked, suggesting that it may have been a yucca of some kind. I could see the rosette of green leaves that may have led her to think it was a yucca, but I said I thought it looked like a cabbage tree, although I had ever seen one with such a large flower.

This weekend, I took a more leisurely trip back to have a proper look and to photograph it. What is remarkable about these two plants is the spectacular height the flowering stalk has reached - more than two metres. Unfortunately, I cannot determine what cultivar they are and whether they always flower like this or if it is an aberrant growth pattern - indeed, I am only 90 per cent sure they are cabbage trees.

Cabbage trees - ti kouka to Maori, cordyline to botanists - are archetypical New Zealand plants, almost as ubiquitous as flax plants, and probably a little bit neglected in the home landscape. This is no doubt partly due to the interesting way the lawnmower takes to their fallen leaves. Most gardeners will have had the frustration of wrapping what seem like indestructible spent leaves around a lawn mower blade but, on the other hand, the various cultivars of cordyline do offer a fabulous contrast to the shapes we normally associate with native flora, their regular rosette-shape allowing a degree of formality to appear among the indigenous plants. If your passion for mowing overpowers your desire to grow some of these native beauties, best find a part of the garden at the back of a shrubbery or the like, where their shed leaves will not cause such offence, or try some in pots, to which they are admirably suited.

In the past few years, several new hybrid cabbage trees have been released to the market and, although the colour range has not quite matched the range of colours available in flaxes, it is fast catching up and it may only be a matter of time before there are a similar variety of shades available.

There are several purple-coloured forms but the most popular is probably Red Star, which has good strong roots, excellent colour and a compact growth habit. It does fabulously well in containers and seems remarkably hardy in most situations. Purple Tower is darker coloured, and was once the most popular of the purple/red forms - it is still a good variety. If you are looking for a smaller growing form - the foregoing could grow to about three metres - then go for the petite Red Fountain. Derived from a mountain species and with a more clump-forming habit, this one will grow to about a metre high, with a similar girth and has deep-red, strap-like leaves. Again, it does well in containers or as a lower planting in a shrubbery. It does not like being too wet, so well-drained soil on the dry-ish side is probably perfect for this variety. I have seen this variety in flower in a large clump at the Auckland Botanic Gardens, and the delightfully subtle scent is heavenly - like jasmine but not at all overpowering.

The first of the variegated forms commonly available was the green and white form Albertii. Not only does this variety sport dramatically coloured leaves, the base of the leaves is coloured intense salmon pink. This looks great as a young plant, perhaps looking its smartest when grown in a container with some contrasting leaved plants around it.

I think it starts to look a bit tatty as it grows older and the variegation does not seem so intense.

These plants used to be rare and extremely expensive, but the advent of tissue culture has made them more common, and fortunately also much cheaper.

Needless to say, some clever plant breeder thought it might be a clever idea to cross the purple-foliaged forms with the variegated forms and we now have quite a range of colours to try out, including a range of green-leaved forms with varying degrees of red stripes, either in the centre of the leaf or along the margins, and bronze forms with pink stripes.

Perhaps the brightest hybrid, though, is a form of the smaller growing species C. banksii, with the well-deserved name of Electric Pink. This is a clump-forming cultivar with leaves that are deep maroon with shocking pink flashes - truly electric and more than a little outrageous.

If you have the room and the budget to cope with it, this makes a spectacular clump, and would look great associated with some larger-leaved plants, such as Chatham Island forget-me-nots.

Many of the coloured varieties seem to lose colour as they age - don't we all - so it probably pays to apply some fertiliser to them as they get older.

An annual application of a long-term fertiliser should do the trick, or some well-rotted animal manure worked into the soil around their roots.