Tuesday, November 20, 2007

Letter to Uruguay

The following was written to Amalia Robredo, a pioneering garden designer in Uruguay, who is experimenting with designing with native plants and sculpting the existing vegetation of the Uruguayan coast - a dwarf shrub formation known as the Monte. It is pretty relevant to anybody in similar circumstances.

I am trying to think through what I would do if I beached up in a country with no tradition of ‘wild’ or naturalistic gardening or of using its native flora for gardens or landscapes. There is so much to do! But the rewards are to be a pioneer, to achieve a quantum leap, and perhaps even be remembered for it by future generations!

All too often a mystery - Plant lifespan
First of all, we often know so little about how wild plants behave in cultivation – there are certain basic facts that need to be established. So, even if you are planning to grow native plants only in wild-type communities, I think it pays to cultivate a few specimens of each species in the garden too, in order to learn about them. One of the key issues is plant lifespan, and the related topic of how they reproduce themselves. It is usually fairly obvious if something in the wild is an annual – they always produce masses of seed from a stem which enters the ground to connect to the roots at a single point. Less obvious are those short-lived perennials like Verbena bonariensis (which I am fascinated to learn from you is a wetland plant in its native habitat). They can play tricks on us – we think they are perennial but then die after a couple of years, a situation not helped by the inadequate terminology we have adopted for plant lifespan: annual, biennial, perennial – there is no recognition here of the ‘short-lived perennial’ category.

Annuals, biennials and short-lived perennials nearly always set plentiful seed which germinates rapidly (they would soon become extinct if they did not), and they do not form clear ‘ramets’ at the base. A ramet is a term (used by botanists and ecologists rather than gardeners) to describe a shoot at the base of a plant which grows its own roots and can become, in time, independent of the parent plant – such things sort out the true perennials from those of limited lifespan. Short-lived plants will generally self-seed, but are able to do so only on disturbed ground and are, over a number of years, replaced by longer-lived species. So, thinking about their ornamental effects, these may be spectacular but transient.

The Joys and Frustrations of Propagation
Growing a few native plants in ‘garden’ conditions is also an opportunity to learn about how they might be propagated. Becoming knowledgeable about propagation is something which is almost inevitable if you are experimenting with plants. There is something addictive about it – the thrill (and sometimes challenge – sometimes deep frustration) of making new plants – new life! Some people become obsessed with propagation – either they cannot stop making new plants or they take on the challenge of species which cannot be propagated so easily: cuttings which refuse to roots unless given some special treatment or seed which does not germinate unless likewise some magic is performed, even dipped in sulphuric acid!

Propagation ‘tendencies’ tend to go in families: compositae/asteraceae germinate quickly, labiatae cuttings root in a week; but herbaceous always tends to be easier than woody. Particularly frustrating are really beautiful plants you want lots of but where cuttings rot away after months of sitting in compost or have seeds which simply do not come up.

The truth is that you will end up with far more of the easy to propagate plants than the difficult ones. So cultivation ends up being dominated by plants which are easily propagated. For work with native plants, this tends to mean domination by the species which are important in the early stages of succession; species which dominate the established plant community (places which have been undisturbed for centuries) tend to be slower to grow and to spread themselves.

Whatever – you ought to make sure you have some good books on propagation!

The Cultivar Dilemma
When native plants are taken into cultivation, it is very often as cultivars – selections made for a variety of reasons: bigger, brighter flowers, longer flowering season, more compact habit etc. But behind these very obvious and prosaic reasons lies perhaps a deeper, cultural issue. Just as very few Uruguayans probably appreciate the monte, so few will appreciate native plant species. There is something fundamental about the human relationship with nature which demands that we separate ourselves off from it: so Australians despise the bush, Brazilians the jungle, Americans fear the forest (unless neatly packaged as National Park) etc. So, it should come as no surprise that ‘native’ plants are somehow made more acceptable once cultivars are chosen. They also help market the native plant as a product – consumers after all will be more likely to pay for a plant which bears a name they can relate to; this name also signals a kind of domestication: Solidago rugosa ‘Fireworks’ is going to sell so much better than plain Solidago rugosa, even though it is practically identical.

A great many plants in cultivation are simple selections from the wild – good forms which are then propagated so that they are all more or less identical. This is why vegetative propagation is so important for cultivars: division or cuttings, or grafting. Seed-grown, ie. sexually propagated, plants will nearly always show a range of differences between each other and the parents – and so cannot be relied on to ‘breed true’. With woody plants: shrub and trees, this is why vegetative propagation is so important – as a way of ensuring that what is identified by a cultivar name maintains the set of characteristics for which it was selected in the first place.

So, I would argue that a key part of domesticating native plants and making them popular is the choosing of good cultivars: the great plant hunters very often did this in the wild by taking seed from individuals they knew to be particularly good. The garden owners and nurserymen back home would line out hundreds of plants grown from the seed they sent back, and then select just one or two to propagate from – and of course give cultivar names to.

However, there is a catch.

If you are interested in really using native plants to create a naturalistic style of planting, you want them to reproduce, to seed themselves around, just as they do in nature; if they do not then the plant community you have will be static, and vulnerable to incursion by less desirable weedy species – often aggressive, non-native weeds.

Cultivars do not always propagate from seed – sexual reproduction is often dependent on plants being genetically different; and if they do, the results will show little genetic diversity. Genetic diversity is important for self-sustaining ecologically healthy plant populations. So, the implication is, that for creating genuine plant communities, cultivars are not always such a good idea, however good they might be for getting people attracted to and interested in, native flora. Cultivars are fine for those making conventional gardens, but if you are trying to create something wilder, where the role of the gardener is more ‘hands off’, where you want a dynamic plant community which regenerates itself – then cultivars are not so good. Instead you want multiples of seed-grown individuals, ie. plants of different genetic make-up.

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