Wednesday, June 28, 2017

Scarlet lily beetle

This year, for the first time, scarlet lily beetles Lilioceris lilii appeared in my garden. There were only two, which turned out to be a male and a female, and they came with some lily bulbs imported from Holland that I bought in a supermarket.

Being curious, I kept them under observation in a jam jar and soon discovered why these lovely insects are considered to be such notorious pests.

They mated overnight and by the next day had begum to lay rows of their round-ended, cylindrical eggs on the lily leaves that I supplied to them.

The adult beetles are formidable eaters, quickly nibbling holes in the edges of leaves that I gave them to feed on, but the grubs, when they hatched a few days later, were in a different league altogether.

They quickly began chewing holes in leaves and half a dozen of them could demolish a lily leaf in less than a couple of hours.

But, most remarkably, they did this while covering themselves in their own frass, which camouflaged them as bird droppings. This one has only just begun to anoint itself but they quickly became completely hidden in a mound of their own droppings.

From a gardener's perspective, these are extremely destructive insects and I can quite see why, in the worst affected parts of the country, gardeners have had to give up growing lilies. 

These gaudy insects have spread from their native Eurasia throughout most of the temperate northern hemisphere.  They first appeared in England in a Surrey garden in 1939 and by 1943 had reached the United States. Their spread northwards in England, and now into Scotland, has been rapid in the last decade, no doubt helped by a wholesale and retail distribution system for lily bulb sales that has ensured that they can reach every part of the United Kingdom.

I never once saw them attempt to fly. If you disturb the adults they just fall off the plant and pretend to be dead until the danger has passed.

The Royal Horticultural Society has a very good web page devoted to these insects and is also conductiing a survey of their spread, although I have to say the words 'horse', 'bolted' and 'stable door' come to mind!

These two individuals were the only ones that appeared in the garden and my lilies are doing fine, almost flowering in fact, but I wonder whether I'll be so lucky in future years

Tuesday, June 27, 2017

Monkey flowers: summer opportunists when river water levels fall

In summer, when the water level in the upper reaches of the river Wear drops, its gravelly banks are colonised by a natural rock garden of plants. This year, after a long dry spell, its flora is looking particularly attractive. Many of the plants are garden escapes, most likely from garden refuse swept down the river from upstream. 

The most eye-catching are monkey flowers, whose creeping stems become woven into the coarse gravel and resist the flow of the current when the river rises again. The most beautiful is the coppery monkey flower Mimulus x burnetii, a sterile hybrid between Mimulus guttatus and M. cupreus, both from western North America.

It isn't very common because it does not produce seeds and only spreads from vegetative fragments, but wherever it does appear its warm coppery tones make it very conspicuous. 

This is one of the parents, monkey flower Mimulus guttatus, which does set seeds and is a colourful feature of the river gravels all along the upper reaches of the river Wear.

Both plants are very easy to propagate - just a short length of the creeping stem with a leaf node will produce new roots and shoots very quickly.

Sunday, June 25, 2017

Orchids on the Durham coast

Durham's magnesian limestone grassland is famous for its orchids. Yesterday, when we were walking along the coast near Hawthorn Dene there was a sensational display, in the hay meadow at the mouth of the dene itself and even more so in the thin soils around the old quarry. 

There were many hundreds of spotted orchids and scores of pyramidal and fragrant orchids. There were also plenty of twayblades, but it's hard to estimate their numbers because their green colour makes them easy to overlook. 

I think this was the best orchid display that I can remember here.

Fragrant orchid

Pyramidal orchid

An albino common spotted orchid

Common spotted orchid

Twayblade orchid

This is the area around the quarry with the highest density of orchids, growing in a thin veneer of soil over limestone. Other species in flower here included centaury and yellow-wort, greater knapweed and carpets of bird's-foot trefoil.