Sunday, 26 July 2009

Mediterranean and Sub-tropical

A couple of years back I was very excited to read the catalogue of a nursery called Koba Koba, based somewhere down in Devon. (I just checked - they've closed apparently.) I was excited because they were offering a substantial list of 'hardy' gingers and other 'hardy' subtropical plants such as Musa (bananas) and Amorphophallus (those extraordinary giant Arums that stink of rotting meat) and at the time I was very drawn to the whole 'hardy exotics'/'architectural plants' thing. The plants they offered had always interested me but like most gardeners in the UK, I'd thought of them only as specimens for tropical greenhouses and conservatories. A book on the subject (Hardy Gingers by T.M.E.Branney, Timber Press) came out and I duly obtained my copy.
I was aware that some genera in the family (Hedychium, Roscoea, Cautleya) included some good hardy species but was astounded by the variety of what I had previously considered truly tropical groups (Zingiber, Alpinia, Costus, Kaempferia and Curcuma for example) that could tolerate apparently much lower temperatures than we have experienced in this part of the world for many years (-12C for Alpinia zerumbet, -15C for Costus speciosus for example). I couldn't wait to try some.
What was not apparent until I got over my euphoria was that these temperatures are only tolerated if the roots are kept completely dry in the winter.
I'll let that sink in for a moment...
That's completely dry. In the winter... In the UK...
Clearly someone has a funny idea what 'hardy' means but I hesitate to say that they were deliberately misleading us in order to sell plants (or books) but I have a more interesting point to make here because this was the first time in my 20 years gardening career that I had genuinely understood the importance of climate in gardening beyond merely taking into account a plant's tolerance of cold.
What we perhaps forget, living in the UK where it seems to rain more or less equally all year round, is that in many parts of the world, and not just the tropics, there is a definite wet and dry season. We in Northern Europe actually live in a winter wet part of the world. It doesn't seem like it much of the time because Britain has a maritime climate (remember your high school geography) which is never dry for long, but travelling due east, across Europe and into Central Asia it becomes increasingly obvious how much of the year's rain (or snow) falls in the Autumn-Spring period, and, saving a few thunder storms, how little falls in the summer. The difference is striking even between Devon and Essex if you look at the statistics. The Mediterranean area is, as I understand it, just the southern limit of this temperate winter rainfall zone, where summer heat is high enough to cause enough evaporation to create a semi-desert environment. The amount of rainfall annually is not that different to northern Europe.
Similar environments (known as 'Mediterranean' for short) can be found wherever similar situations occur all over the world, where the temperate winter rainfall zone slips equatorwards along the west coast - in California, parts of northern Chile, the Western Cape of South Africa, and the southern corner of West Australia. These regions are unusually harsh environments - the hot and dry seasons coinciding means that most plants are active in the winter and dormant during the summer (spring bulbs for example.)
A lot of plants from these areas will not tolerate freezing (although a surprising number will - at least to -5C) but generally, 'Mediterranean' plants are relatively easy to grow in the UK because we have something like the same climate, with relatively dry summers. As long as the plants are grown in the sunniest spot available and the soil drains very freely they can be extraordinarily hardy. They're especially useful in situations that become completely parched in summer - on chalk and sand soils for example, and up against south and east-facing walls. They also tolerate the drying effects of hedge and tree roots as long as they will also tolerate some shade.

Not so for plants from summer rainfall areas. Mediterranean climate areas cover a very small part of the world but summer rainfall is normal over almost all of the rest of world's land surface. We are used to hearing about the hurricane season in the USA and the Monsoon in India or Thailand, but it's much the same throughout southern and eastern Asia, eastern and northern Australia, much of South America and almost all of Africa. The only exceptions are the equatorial tropics where the rain falls all year round and where the rainforest dominates (or used to) and the zones between the winter wet Mediterranean areas and the summer wet subtropical areas where almost no rain falls at all. This is where the major deserts form.

Much of this area is far too tropical to provide plants for our British gardens but where the summer rainfall zone slips polewards along the east coast it takes in parts of temperate Eastern Asia, south eastern Australia and New Zealand, a small part of south eastern Africa, parts of South America and a large slice of southern USA and Mexico. In these areas the winter temperatures can be similar to those we get here, but without the wet.
So were the 'hardy gingers' a bit of a scam? Well, maybe. But summer rainfall plants aren't as useless as you might think. Many of them come from remarkably cold parts of the world. The deserts of North America extend all the way into Canada and provide us with some incredibly frost tolerant cacti and Agave. Even plants from as far south as Arizona and New Mexico, Alabama and Georgia may suffer much harder winters than we do. Plants from Patagonia and parts of central China are in a similar position. The Eastern Australians and Africans are generally less frost tolerant but especially if they come from upland areas, they can be amazingly adaptable too. The Agapanthus, Kniphofia, Phygelius, Galtonia and Crocosmia we grow come from the highlands of east Africa. The area from southern Brazil to northern Argentina gives us many good garden Salvias (uliginosa, guaranitica, involucrata), Passiflora caerulea, Abutilon megapotamicum and Gunnera manicata. Australia is less generous but this may have more to do with the quality of the soil than the climate. I have kept Banksias, Correas, Lomatias and Grevilleas from New South Wales outdoors all year round in pots for the last fifteen years, and lost none except a Correa I planted out last year. The trick is to keep them as dry at the root as possible - it is commonly believed that any plant of doubtful hardiness will be better off in the ground as the soil will insulate the roots but this is not necessarily the case. Potted plants dry out quickly, especially if somewhat root bound. Thus it helps if your 'subtropical' plants are drought tolerant desert dwellers.

The problem then with the 'hardy gingers' mentioned above is that, during the growing season they are not at all drought tolerant. Alpinia, Costus and Curcuma are woodlanders and need moist, rich, even wet soil during the summer, as do the Amorphophallus. I can't think of any way of arranging the wet summer/dry winter regime these plants need in the open garden in the UK unless it's by lifting them in the winter and storing them like Dahlias (which are of course the classic winter rainfall plant). Not all plants put up with this sort of disturbance.

One final point I must add. Along with the wet summer many of these plants require, is a need for heat and light during the growing season that is often hard to provide in the UK. Plants from the southern states of the USA for example may experience freezes like nothing we see here, but the summers are long and hot and, in between storms, bright and sunny. An extraordinary plant like Hibiscus coccineus is totally frost hardy but may not come into growth early enough to flower before the autumn frosts cut it back down again. Some Hedychium have similar problems. If we want to grow these fabulous plants we may have to borrow some tricks from the vegetable growers - using black plastic to heat the soil up early for example. They'll need siting in the hottest possible situation and yet in a spot that is moist and fertile. A west facing wall may help.
On the other hand, in the deserts of Australia and Arizona for example, a bitterly cold winter night is typically followed by a bright dry winter day. A south or east facing wall or similar is our best hope for these plants.
Finally, woodlanders from the monsoon zones of southern and eastern Asia (Tricyrtis, Arisaema, Calanthe, Anemonopsis, Deinanthe, Asarum etc etc) do not tolerate the dry summers we have in eastern England at all well, exacerbated as it is by trees, sucking up every last drop of moisture. They will enjoy a dank north-facing exposure and a woodsy soil without nearby trees rooting into it.

Ok, that's more than enough for now. You will have noticed that I don't feel the need to write my blog in little twitterish 'sound-bites' as seems fashionable, and actually, I really like the old essay form, or a good solid article in a 'proper' journal. I hope you have the stamina and find it worthwhile.

Friday, 10 July 2009

Hydrangea serrata Kiyosumi

Hydrangea serrata Kiyosumi, originally uploaded by peganum.
Hydrangea serrata Kiyosumi
A typical lacecap Hydrangea in many ways but with two unusual features - the sterile florets around the edge of the inflorescence are white, edged with pink (but tastefully so), and the new foliage is a rich maroon red.
Hydrangea serrata Kiyosumi
A striking small shrub (about 4ft high) for semi-shade on most soils as long as not too dry (including chalk. Hydrangeas are among those plants often believed to be lime-haters. This is not the case.)
2L pots ~ £9

Saturday, 4 July 2009

Scientific names or not, as the case may be

I was thinking my blog list was looking a bit empty today (Hi Paul!) and so thought I'd have a look around at what sorts of things other gardener's blogs are on about. After a quick look, I've not come across anything like this one - most seem to be either about growing veg or conservation (and good for them). We're all about growing something unusual just for the sheer hell of it here. It doesn't have to be useful. It doesn't have to be especially rare. It just has to be something interesting that you don't see every day. Hopefully we'll fill a niche.

I came across this on Garden Rant (excellent name by the way - I love a good rant) about the use of scientific names. There's a long discussion pro and con there if you're interested. It's an issue I come across from time to time and you'll have noticed I use them all the time.
Most people I deal with seem to accept it - they too are plant fanatics and take the names for granted. Other people I speak to though - non gardeners and people who 'just want their yard to look nice' can seem a bit bemused. Most of the time I just tend to say "well just come and have a look and see what appeals to you and I'll give you some advice on you how to grow it" and they seem happy with that. After all, you don't need to understand your boiler to get hot water. A small minority though do seem to see my use of the latin as in some way elitist, snobbish, exclusive. (It's not really latin of course, scientific names are not only cobbled together from latin and classical greek but also incorporate modern people and place names and even local 'common' names as in the Japanese Kirengeshoma.) Interestingly, it's not the non-gardeners who tend to feel this way but rather, people who've been gardening for years and never seen the need. They can be very put out indeed.
So, scientific names. Why? Firstly - there's a time and a place. If I was concentrating on growing local native species for conservation for example I'd use the local vernacular. Likewise if I was growing fruit and veg or a very traditional garden of historically important herbs and flowers no doubt I'd stick to the perfectly good common names. I wouldn't say "I'm just going out to trim the Taxus baccata" or "How many Daucus carota do you want?"
But a quick look through even my modest catalogue makes it pretty obvious that this method breaks down in the face of the sheer quantity of plants from all over the world on offer these days. What would these 'traditionalists' prefer me to call Weigela middendorfiana? Middendorf's weigela? One suggestion was 'The Yellow Weigela', which was interesting on two counts. Firstly it's not the only yellow Weigela. Secondly of course, Weigela is a scientific name (commemorating someone called Weigel presumably). What a lot of traditionalists seem to forget is that many of the names they take for granted are scientific names - Rhododendron, Forsythia, Hydrangea, Delphinium, Geranium... and frankly, if you can wrap your tongue around Chrysanthemum you can handle pretty much anything. The biggest difficulty I find is when the name commemorates a Russian - take Molly-the-Witch as she is affectionately known among the tongue-tied (Paeonia mlokosewitschii). Or what about Ligularia przewalskii?
There's a certain amount of verbal contortionism involved here. The Ligularias used to be classified in Senecio - home of ragworts and groundsels. Siberian ragwort? Well actually there's a lot of Ligularias from that part of the world. I wonder what the locals call it, whoever they are? And then I wonder if we could pronounce it?
Some scientific names are claimed to be descriptive, so a simple translation should be possible. (The spider plant is my favourite - Chlorophytum. It means 'green plant'. How helpful is that?)
Let me think of a good one...
Ok, Hedge-garlic-leaved bell-flower. How's that? Easier than Campanula alliarifolia? It is fairly descriptive as these things go but there are several species fitting that description. You'd have to add 'pink' to the front perhaps to distinguish it from the very similar C.makaschvillii, and maybe other descriptions to avoid confusion with C.ochroleuca which is very similar. This is one of the problems - many gardeners just don't realise how many species there are out there. To those of us who only frequent garden centres it might appear that Campanula alliarifolia and Weigela middendorfiana are pretty unusual for their kind, but unfortunately they're not. They each belong in a group of similar species. Perhaps the traditionalists would not bother to make the distinction, and sometimes to all intents and purposes it doesn't matter that much.
How much it does matter really depends on how well the botanists have done their job. If they've simply been out there in the hills, giving new names to things that really aren't new, just to get their name on a scientific paper (as some gardeners suspect) then we are right to to ignore them. On the other hand, unfortunately, the criteria on which the botanists identify a new plant are often beyond the expertise of the average gardener or even other scientists. We have to take their word for it a lot of the time. And this unfortunately is the main point. Plant nomenclature is borrowed from the scientists. They do things differently. There is nothing to stop us as gardeners setting up our own horticultural nomenclature if we so wish. To some extent we already do - we classify plants according to whether they are edible or not, what colour the flowers are, whether they are hardy or not. The regulations on the use of cultivar names (the names of forms and hybrids of plants not found in the wild but originating in cultivation) are amazingly strict and often infuriating to gardeners (and the results can be cringingly unimaginative - how many Golden Queens and Blue Fountains and Ruby Dwarfs do we need?) But again, the number of types available is easy to underestimate and some form of system is needed if you're at all choosy about which one you want. You can't just ask for a damask rose or a lavender and be sure of getting the same thing you saw in that garden in Cornwall. You need to know the name, and it probably won't matter whether you are looking for Mme Zoetmans (how descriptive is that?) or Lavandula stoechas.
Which brings me, at last, to my final point - that actually the scientific names can, once you get the hang of them, be every bit as easy to say and to remember as the vernacular, and can be as evocative. I'm not sure anyone knows for sure how Latin should be pronounced, and as I said, it isn't strictly latin anyway, so, if in doubt, as with Spanish and Italian I tend to say the names phonetically. The references to people and places can be pronounced however the people and places are normally pronounced and as for the rest, well, my best advice is don't rush at it. Like being back at school, look at the word, take it apart, say the parts, get used to what they sound like in your mouth, and say it with confidence - Kirengeshoma!

Now people's names - they are a problem...