Yuccas not Yukkies

If you like your plants spiky and architectural, this is for you.
Angus White, Architectural Plants, Cooks Farm, Nuthurst, Sussex
Chamaerops No. 7, published online 23-10-2002

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Left: Yucca recurva - or is that recurvifolia?
Right: Small but beautifully formed - Yucca whipplei.

Some people don't like Yuccas. They think they are nasty spiky things and call them "yukkies". They think this is terribly funny and rather clever which, of course, it isn't. These people are hopelessly deluded and the only reason they feel like this is because they're boring and stupid. The people, that is, not the Yuccas.

That's the nice thing about writing for a magazine like this; you know you're preaching to the converted and can really get your rocks off.

Having said all that, it's quite true of course - they are nasty spilcy things. Some of them are vicious in the extreme, but, they're also - at least some of them are - beautiful dramatic, exotic and bold. They didn't get their common names such as "Spanish Dagger" and "Bayonet Plant" for nothing you know.

They all come from the New World, most from the southwestern United States, some from the southeastern and central United States and some from Mexico and Central America. The best-known and hardiest ones grown in the British Isles come exclusively from the United States. They all look spiky to a greater or lesser extent and they all send out tall flower spikes covered in masses of almost spherical flowers between pure white and cream. An essential point to grasp right at the beginning of the road to Yucca-enlightenment is the two broad groups into which the Yuccas fall:

1. The Clump Formers. These consist of many separate plants within a clump. When an individual flowers it subsequently dies but is replaced by more shoots, so the clump is preserved. The individual plants never form what could be described as a trunk.

2. The Trunk Formers. Botanically described as arborescent, these form trunks on which the rosette of spiky leaves always appears to sit. When they flower, instead of dying, they branch. Flowering can result in two, three, four, or even five new shoots being created. Each shoot then goes on to create its own trunk - or what one would normally refer to as a branch.

Intelligent Cultivation

Yuccas are and have been for some time, grown quite widely in Britain. The common perception of their desirability seems to be largely based on their dramatic flowers rather than the wonderful architecture of the plant itself. Therefore, little thought seems to go into the subject of how the plant actually looks for the 49 weeks of the year when it's not flowering. As with so many plants, it's a simple matter of standing back, looking at your plant and asking yourself whether it really looks the way you want it to and if it doesn't, what are you going to do about it.

Trim & Feed

Remove old, dead and tatty leaves and dead flower spikes and get the plants to grow vigorously by plenty of feeding (springing 'Blood, Fish and Bone' round the plant in the spring is very effective). You might have to remove branches that have formed following flowering in order to create a single trunk, remove suckers to encourage healthy top growth or just remove the brown bits. It only requires common sense and a little imagination.

Once one gets into this more 'manipulative' attitude towards growing things - a whole new world opens up. It's so easy and yet it's so rarely done; people don't do it because other people don't do it and they apparently think that other people don't do it for a reason. What reason? I don't know - maybe they've just never thought about it.

Thoughtful Approach

At our nursery we spend much time going on about this more 'thoughtful' approach to growing plants. Healthy plants grow more vigorously, have more new growth on them and therefore look better. Remove the brown bits, avoid trying to grow inappropriate plants in inappropriate places (Trachycarpus palms on the front at Shanklin?) and use your secateurs in a creative and thoughtful way. What could be simpler? Despite this apparent simplicity, Japan is the only country where such an approach is part of their horticultural tradition; they have a great emphasis on evergreens, non-flowering plants and their sculptural qualities. In Europe the emphasis is so often on flowers and little else; thoughtful cultivation extends little further than topiary and the pruning of fruit trees.

It could be the mystique that surrounds the correct pruning of fruit trees, rose bushes and other flowering shrubs that inhibits the creative use of secateurs. People actually seem frightened to use them. "But will it be all right?" is a frequent rejoinder to the suggestion that someone cuts off the old flower spikes and dead leaves on a Yucca. Yes, is the answer, it will be all right. As with any idea that people are not familiar with, the vocabulary surrounding it is an important tool for getting the idea across. One has to experiment before coming up with the necessary 'catch phrase'. It is 'manipulative' but I must confess to finding that word has too many unpleasant associations to be a useful adjective in this case. I quite like 'thoughtful', because that is exactly what it is...any suggestions? Maybe there's an expression in Japanese that could be translated. Intelligent cultivation?

Brown Bitting

As the plant gets older, the old leaves die, hanging down on to the slowly forming trunk (unless it's a Clump Former in which case they lie on the ground looking grim) - just like a palm tree. For aesthetic reasons already mentioned, these dead leaves need removing. The contentious issue here is whether to pull them off or to cut them off as near to the base as possible. For a nice clean trunk, pulling the old leaves off is essential. BUT, if this removal goes too far up towards the new leaves, the dreaded rot can be introduced. Once the trunk of a Yucca gets rot into it you must snap into action as soon as the ghastly discovery is made (bad smells and black soggy bits). Surgical removal of the offending area with a sharp knife followed by liberal applications of a powdered fungicide (Benlate, for example) rubbed in well with the finger is a sure remedy.

Sun Or Shade?

More contentiousness. If it's thought that the most attractive aspect of growing Yuccas is their spectacular flower, then a position in full sun is essential. BUT, is the most attractive aspect of growing Yuccas their spectacular flowers? With the clump forming species like Y. flaccida or Y. filamentosa then the answer is probably 'yes'. Any other redeeming features they might have are not immediately obvious - so why not enjoy the flowers? Some of the trunk-forming Yuccas consist of a single rosette of leaves that have a beautiful symmetry. Once a plant like that has flowered, new shoots will emerge from amongst the head of leaves and the symmetry will be lost. Having cast doubt on the desirability of the larger Yuccas flowering, we need to investigate ways of discouraging them from flowering. So far, there's only one way we know, and that's growing them in the shade.

Some Of The Hardy Yuccas

Yucca aloifolia: One of the most distinctive of all. We have a specimen that was dug up from a Chelsea garden because it was "just too big". It had reached 12 feet in about 15 years. This is unusual and reflects the warm microclimate found in Central London, but even in rural Sussex we have specimens of 4 or 5 feet that survived a low of -17c in February 1991. Despite this they are not as hardy as some Yuccas and need careful positioning in warm spots with perfect drainage. They only flower very reluctantly so measures to stop them flowering and branching are quite unnecessary plus they wouldn't do well in the shade anyway. They have leaves that persist for a long time, sticking horizontally out from the trunk, which usually has a diameter of some 4-5 inches. The leaves have the most vicious points of probably all the Yuccas and yet the profile of a well-grown plant is quite soft - I always think of it as the prettiest of the Yuccas, despite its horrible armament. There is a variegated version, which is occasionally available. Smaller and slower growing but just as dangerous. It's very beautiful but rather more frost tender.

Yucca recurva or recurvifolia: Look it up in your plant book and it'll rather unhelpfully tell you that this plant has recurved leaves; an expression I had a lot of trouble with (i.e. I didn't know what it meant) until I realised it meant bent. So the leaves go up when they leave the plant and then half way up they bend and go downwards. The newly emerging leaves don't bend, they go straight up, it's the older leaves that recurve. A well-grown and vigorous specimen on a single trunk is a fine sight; elegant, exciting and very frost hardy. This plant is considerably m ore prone to flowering that Y. aloifolia and so a suitable candidate for the shade. Some of the most magnificent specimens I've ever seen anywhere are in the Cornish Gardens - whether in the sun or shade, but only because they seem to grow such huge heads of leaves. I'm sure this is a function of their reluctance to flower probably due to the cooler summers encountered in that part of the world. In the southeast, with its warmer summers, growing in shade is probably the only way to inhibit flowering.

Yucca 'Vitoria Emmanuel II': A magnificent monster of a plant, a hybrid, (originally bred by Carl Sprenger in his nursery in Naples in the I 870s), between the two previous species - Y. aloifolia and Y. recurva. This one is worth growing for the flowers; it combines the frequency of the flowering of Y. recurva with the hugeness and brilliant whiteness of the Y. aloifolia parent.

Yucca gloriosa: The classic Yucca beloved by Victorian gardeners with its thick trunk and stiff straight or incurved (opposite to recurved?) leaves. Despite being so well known a difficult plant to acquire. Like so many plants, the more you get to know about it, the more confused you get. There seem to be so many forms, I sometimes wonder if I've ever seen two the same. By far the most spectacular plants I've seen, are multi-branched but on a single and very stout trunk of some 3-4 feet. So the plant couldn't have flowered for the first 5 to 10 years of its life. Why? Possibly because they are grown from seed. Seed of Yucca gloriosa is unobtainable in our experience because the flowers can only be pollinated by the Yucca Moth, which only exists in certain parts of the United States, and even if viable seed was formed, what form of Y. gloriosa would you get? Normally, this plant can only be propagated by division or rooting occasional offsets. As with any vegetative form of propagation, this means that the new plants will think they are mature and ready for flowering - and one is back to this problem of preventing them flowering at an early age. Interesting isn't it? The variegated version of this plant is produced by micropropagation and is therefore fairly widely available. As with all variegated plants, smaller and less hardy than the type, but still reliably hardy in most of Britain and a splendid looking plant.

Yucca X floribunda: This plant is widely sold as Yucca gloriosa throughout Europe, but it isn't. We are now quite sure of the identity of this plant, a hybrid between the clump forming and very free-flowering Y. flaccida and good old Y. recurva. Plant this in a sunny spot and disaster will ensue. It almost flowers itself to death. Yes, it flowers like mad, but the Y. flaccida parent says "you have flowered so you will die if you don't send up new shoots from the ground", so a forest of floppy leaves emerges from around the original plant and the Y. recurva parent says, "you have flowered, so you must branch". The result is a most unholy mess of leaves and exhausted branches, usually resulting in the eventual demise of the original trunk. This is the plant for shade - even dense shade, where flowering is most unlikely and a single trunk with a lovely rosette of leaves will be the result. Immensely frost-hardy, this is the sort of plant to use where something like a Cordyline australis wouldn't be sufficiently hardy.

Yucca glauca: Lots of very straight narrowish bluish leaves, forms a small trunk, rarely flowers but doesn't die if it does. Understand? So hardy that it would probably thrive on Baffin Island, this is a landscape plant that needs to be used in relatively large number to create a really good effect. In a good rich soil, this could reach 4 feet across and 3 feet high. Removal of the old leaves (Brown Bits) and prolific planting is about the extent of Intelligent Cultivation that can be used on this plant.

Yucca whipplei: When small, this can be confused with Y. glauca. A clump former with long thin bluish leaves, very sharp at the ends. Eventually grows anything up to 8 feet across with a massive flower spike up to 15 feet tall. This plant has a wide geographical range between the Californian Coast, Arizona and Mexico and the usual confusing array of different forms and different degrees of frost hardiness. This will account for the apparent confusion of accounts as to where you may or may not grow it in the British Isles. Undoubtedly a very impressive plant but a very slow grower in its first few years.

Some other impressive looking Yuccas that need further investigation: Yucca rostrata, Y. schottii, Y. thompsoniana and Y. treculeana.

Finally; many of the books mentioned in bibliographies on this subject are out of print and hard to come by, but, the ten page entry on Yuccas in my Bible, W J Bean's "Trees and Shrubs Hardy in the British Isles", is essential reading with many delightful quotes and purple passages.

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