Tuesday, February 16, 2016

Hellebore troubles

Hellebores can make such a huge impact as they flower so much earlier than anything else. Try cutting them though and they hang their heads so limply as to put you off ever trying again. The only way to cut them is to float them in water as in the picture above.

They are easy enough but I find that many of ours are dying out. Given my interest in long-term plant performance I have been monitoring this and discussing it with other gardeners. The consensus is that from about ten years onwards many do go into a decline. This is not surprising as they seed (or can do) so extensively which suggests something which is not going to be with us for ever. So, all the plants I paid such good money for from Ashwood Nurseries and Wendy Perry all those years ago are now pretty well vanished. They initially seeded well – I dug a load up and planted them out, leaving many others to grow in the bed.

The seedlings I have left, i.e. next to their parents, have never really taken off. Despite it looking like initially they would smother everything else, they have never gotten that big and are now beginning to die too. All I can think is that they cannot cope with the competition of the roots of the overgrown hedge behind them. The very best ones are right up the top where the hedge is further back. Elsewhere in the garden we have a few magnificent plants, but always well away from shade or tree roots.

So, a bit of a crisis for something that was always such a feature of the garden in late winter. The seedlings I had dug up seven or so years ago have done well, breeding relatively true from seed, so we have had some good plants to move elsewhere or give away. It was interesting to note however the difference in vigour and how this was linked to flower colour (genes on the same chromosome?). I had set out the seedlings in order of size in a nursery bed, and all the largest ones turned out to be red, which actually is the least interesting colour of all. The picotees seem particularly lacking in umph. In looking at this lot the other day, I realise that there is only one in the nursery bed left which was worth doing anything with, a very spotty white. So I divided it, feeling as if I was taking the plant's life in my hands as they do not divide well, and you do end up doing terrible damage to them, crushing flowers and leaves as you do so. Hopefully the rather miserable looking divisions with a few leaves sticking out at odd angles will take. The roots are most active in the late winter, when they flower, so this is the best time to carry out this perilous operation.

These seedlings had originally been collected from around good plants, the seeds being so heavy that you can be pretty sure which plant a seedling has come from. I tried to find some more around good ones this year, but it is a struggle, and even when very small, the seedlings have very long roots and can be difficult to extricate from the ground.

I shall have to try to save seed again this year, but this is not easy, because as soon as it is ripe it seems to hurl itself out of the seed pods. I have tried tying little muslin bags (thanks to eBay I now have a whole packet of these) around the maturing pods but they are actually too small – I need the next size up.

Going to buy expensive seed from Ashwood or Jelitto or somebody is going to feel like a defeat, let alone having to take out a mortgage to buy new plants. So we shall have to develop a Hellebore Conservation Action Plan.

Sunday, February 7, 2016

The aliens (might be) landing !

Rhododendron x superponticum dominating waterside habitat in Yorkshire. Maybe the otters like it for cover but I can't imagine much else does.
I wrote the following for Pro-Landscaper magazine, last year - i.e. for a British Isles audience. So please realise that issues may well be very different elsewhere. . . . .

The press love a good invasive alien story. Shades of martians landing and/or man-eating triffids on the prowl. There is often a hint of racism too, invasive plants almost inevitably come with national labels: Japanese knotweed, Spanish bluebells, and the language used to describe them is not unlike that used to discuss immigration issues in certain quarters.

The landscape industry is very much in the front line here, both in preventing the use and spread of invasive aliens and sometimes in their control too. But how much of a problem do we really face?

I would argue that the invasive alien story is in danger of being grossly exaggerated, and those of us who work in horticulture and landscape need to keep a cool head. First of all, we need to realise how lucky we are. While some countries battle enormously damaging invasive species, Britain faces relatively few real problems. We have an amazingly aggressive natural grass flora, which has evolved to benefit from the exceptionally long growing season we have – the result of our being on the north-west fringes of Europe, facing the warm waters of the Atlantic. Our wild grasses have an incredible ability to spread, propagate and suffocate most of what comes in their way. They may create problems in establishing garden or landscape plants but they are a great defence against invaders.

So what problems do we face? The obvious answer is Japanese knotweed (Fallopia japonica); the press love stories about it, and the government has responded by enacting legislation that potentially adds considerable costs to landscaping and construction projects. However, it does not seed, it is suffocated by trees, is easily killed with herbicide, eliminated by mowing and makes little headway against grasses. Neither does it kill small dogs (unlike, we are told, seagulls). It is a big problem in a very small number of localities. The main reason for its spread has been the moving of infected soil, something entirely preventable. It is important to realise it is not going to engulf the country.
'Perspective' is one thing which those who get very excited by invasive aliens find difficult to maintain. Particularly important is to recognise the difference between the spread of a species and it being problematic. Buddleia is a good example. Its appearance on buildings worries property owners (rightfully) but its extensive seeding into waste ground creates an impression that it has capacity to spread. This is liable to alarm those with a dogmatic understanding of ecology, who believe that only native species have a right to be here. Given time, buddleia gets suppressed by native grasses and in particular by our native brambles and shrubs. However even at its most vigorous it grows alongside other plants (and of course butterflies love it).

The plants we need to worry about are those that 1) do not get suppressed by our native vegetation, and 2) get the better of it, even though these may only be problems in particular places. Rhododendron x superponticum is a good example of something that does both of these; spreading even in the shade of woodland and suppressing almost anything which grows in its dense shade. Certain cotoneasters might be another, but only with regard to very localised habitats (cliff faces). With time many seemingly aggressive species decline, as local infective agents and pests discover them – there is evidence that this has happened with Himalayan balsam (Impatiens glandulifera) in continental Europe. Given the costs and difficulties of eradication, keeping a cool head and focussing on identifying real problems, not headline-generating ones, is vital.

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