Saturday, January 16, 2016

Beautiful Bark

Auckland Park, in Bishop Auckland in County Durham, has a fine collection of venerable trees with beautiful bark patterns. 

Hawthorn Crataegus monogyna

Fluted trunk on an old hawthorn ....

.... with an elegant twist

Grey poplar Populus alba. The flat surfaces, between the fissures, are covered with diamond-shaped scars that look as though the bark has been hit with a pick, which is most evident on young trees like the one you can see by clicking here.

The old grey poplars have the most deeply fissured bark of any trees in the park ....

.... with splits so deep that they resemble crevasses 

Young silver birch bark peels away in thin layers (click here for a picture) but as it ages the bark splits and forms flaky plates ...... 

...... like this

Sweet chestnut Castanea sativa, with a bark pattern that resembles raised branching fibres ...

... with deep crevices where all manner of small invertebrates can spend the winter

Monday, January 11, 2016

Chumbawumba tree

Trees are admirably resilient organisms and it usually takes a lot to kill one outright. They can be broken by gales, struck by lightning, flooded, droughted or cut down to ground level and they'll still sprout new growth when spring arrives. Even when they're infected with a fatal fungal disease it can take years for them to die, while all the while they continue to produce seeds. It takes something pretty cataclysmic to kill most trees stone dead.

This rowan, in Backstone bank wood in Weardale, reminds me of the Chumbawumba tune Tubthumping, with its chorus I get knocked down/I get up again/you're never gonna keep me down. If you are not familiar with this particular earworm you can listen to it here. Don't listen for too long - you might never get it out of your head.

It's a mature rowan that was blown over in a gale over fifteen years ago. The windward roots snapped but the leeward roots remained intact and embedded in the soil, so it continued to grow and produce new vertical shoots from the fallen trunk which is slowly subsiding into the woodland floor and is now covered by a carpet of moss. Those new shoots have grown into half a dozen tall, straight trees in their own right.

Where once there was one rowan, now there is a whole row of them. Resilience.

(Double-click on the pictures for a larger, clearer image)

Wednesday, January 6, 2016

Inner beauty of a successful weed

Hedgerows are full of young goosegrass Galium aparine plants at the moment, whose rapid growth has been encouraged by mild winter temperatures. 

This is one of our most successful and ubiquitous weeds, beautifully adapted to fast growth, prolific seed production and efficient seed dispersal.

The seeds, which are covered in tiny hooks and are dispersed in the fur and feathers of animals, germinate in late autumn and early winter so that by spring the young plants have a head start on surrounding vegetation and begin to flower quickly.

The stems elongate very quickly too and the plant is finely adapted to using surrounding plants for support, thanks to ....

... a covering of tiny, backward-facing hooks on the stems and leaves, seen here under the microscope. In fertile agricultural soils the plant can thread its way through a hedge by early summer, sometimes reaching a length of six feet or more and smothering the hedge by the end of summer, all the while producing thousands of hooked seeds from tiny white flowers that are visited by small insects but probably self-pollinate too.

One reason why goosegrass is such a prolific seed producer is that its habit of scrambling over other plants, using those hooks, means that it doesn't need to invest much energy to producing a strong stem. It takes a hawthorn several years to reach a height of six feet, building stem strength through woody tissue production, but goosegrass can reach the same height in about three months.

 This image shows a one cell-thick section through a stem and those yellow stained cells, in a ring in the centre, are the only ones that have any woody strengthening in their cell walls - all the blue-stained cells are pure cellulose. 

The narrow line of yellow staining on the outside of the stem is the waxy cuticle, that protects the plant from water loss.

Sunday, January 3, 2016

Reasons to do nothing

There's a strong temptation to tidy up the garden in autumn, cutting down old flower stems and raking up all the leaves, but there are rewards for doing nothing. 

One is that seed heads provide food for garden birds in autumn.

Another is that dead leaves and flowers can be incredibly beautiful after their soft tissues have rotted away, leaving only the veins that conducted water and sugars through them when they were alive. Our recent wet, mild autumn and winter have been particularly good at revealing these botanical skeletons.

These are the exquisitely skeletonised bracts of an Astrantia flower, that I spotted in our garden today.

Giant bellflower seed capsules

Two skeleton leaves

The seed capsule and bracts of henbane

Flower bracts of Hydrangea

Saturday, January 2, 2016

New Year Plant Hunt in and around Durham city today

A second day of New Year Plant Hunting, this time along the banks of the river Wear and along woodland edges and hedges. Nineteen species in flower this time, of which these are some of the most pleasing:

Alder catkins

Hazel catkins


Nipplewort Lapsana communis

Lesser celandine, flower petals eaten by a slug but very attractive variegated foliage.

...... and cowslip, flowering four months early.

The cowslip was on the Durham University estate, on the Mountjoy site, about 400 metres from an area that was seeded with wild cowslips about 20 years ago. Since then they save seeded themselves on various places, most likely with seed carried on feet of staff and students. This single flowering plant was amongst a population of over 50 non-bloomers, all with very vigorous new leaf growth, on a very sheltered grassy bank under an alder.

Friday, January 1, 2016

New Year's Day Plant Hunt on the Durham coast

Just sent in my list of species that I found flowering today for the BSBI New Year Plant Hunt (see bottom of this post), after walking the cliffs from Seaham to Hawthorn Dene on the Durham coast, 

Despite the mild winter so far it's not a very impressive list - just 14 species. For almost all of them, I'd be surprised if I didn't find them flowering at this time of year, with one exception. 

The only really interesting species in the list is yellow-wort Blackstonia perfoliata. There were scores of plants flowering around the old limestone quarry near Hawthorn Dene. Some were undoubtedly second generation plants that were progeny of individuals that flowered early last summer and these late bloomers have benefited from the mild autumn to reach flowering size and set seed, probably pollinated by small flies attracted to the yellow flowers. 

There were also some robust non-flowering plants that were undamaged by last night's frost and may well survive the winter, to flower very early in 2016. 

B. perfoliata, with it's annual life cycle and overlapping generations, could be a species whose fitness, in terms of overall annual capacity to reproduce, might be enhanced by warmer winters.

It seems likely that there might be at least five main types of plants that are in flower at this time of year:

1. Occasional mutants whose flowering control mechanisms for responding to temperature and/or daylength have been disrupted. A classic example might be the Glastonbury thorn mutant of hawthorn. A number of horticultural mutants e.g. winter-flowering pansies and primrose species fall into this category too.

2. The hangers-on: late summer/autumn-flowering species that continue to flower sporadically if the weather isn't too severe. In genetically variable species there are always likely to be some plants that are more likely than others to perform in this way.

3. Spring-flowering species whose blooming is genuinely brought forward by mild winters e.g spurge laurel, blackthorn and sweet violet

4. Species that have always flowered all year-round anyway and don't need any pollinators e.g. groundsel.

5. Species that might be showing an adaptive response, taking advantage of a changing winter climate. Species are only likely to benefit from this (i.e. have increased fitness, in the sense of leaving more progeny) if they have non-specific pollination requirements and yellow-wort fits this category rather well, since its yellow flowers are attractive to small flies, that are present even in winter and are active on milder days.

Species flowering at Seaham today:

Yellow-wort Blackstonia perfoliata
Wood avens Geum urbanum
Red dead-nettle Lamium purpureum
Ragwort Senecio jacobaea
Common daisy Bellis perennis
Sow thistle Sonchus oleraceus
Gorse Ulex europaeus
Winter heliotrope Petasites fragrans
Bramble Rubus fruticosus agg.
Dandelion Taraxacum officinale agg.
Groundsel Senecio vulgaris
Annual meadow grass Poa annua
Herb Robert Geranium robertianum
Ox-eye daisy Leucanthemum vulgare