Indoor meeting: Talk by Joe Sharman on 'Variegation'
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- Written by: Chris Davies
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13th January 2018
Joe said the organisation of variegated tissues in plant cells can be seen through a microscope. This is where variegation starts from.
It can be caused through environmental conditions, viruses, pattern gene variegation, chimera, of which there are several kinds, and transposons, ( or switching genes).
Joe showed a range of slides of plants illustrating variations on variegation sources and patterns.
Variegation starts in individual cells, at an early stage of cell division, and the same variegation multiplies as that cell divides.
White variegation contains no chlorophyll and these cells are smaller than cream or yellow ones, containing a little chlorophyll, and these are a little smaller than green ones, so that when a white layer of tissue, overlays a green layer, or a green layer is bordered by a white layer, as in variegated leaves, the leaves may be puckered or twisted.
Each layer of tissue in a leaf may be differently pigmented from the others, and this will show as different shades at the surface. The absence of chlorophyll may also affect the proper shape of the leaf because of the cell size differential.
Frost, sunburn, chemical effects and access to specific mineral nutrients can also cause superficial variegation. This will alter in new leaves when those conditions change and wouldn’t be passed on to seeds, or remain in cuttings.
Viruses in cells can cause a range of variegation, some of which is considered decorative. This is subjective. The existence of a virus can be proved if it transmits to another plant.
Pattern gene variegation is controlled by chromosomes in the cell nucleus. This is a source of silver variegation, when the layers of the leaves become separated, and is most often seen in shade-loving plants.
Red and purple colours come from anthrocyanins, when present in the cells. These colours are not linked to the chlorophyll variegation, so are selected separately by nurserymen.
A chimera is composed of more than one form of DNA, Joe compared this to cancer in humans, but in plants it is not necessarily life-threatening. This does not necessarily cause variegation in plants.
Variegation from complete layers of cells is more stable than when the variegation has started from wedges of colours, as in stems.
Examples of sectorial chimeras were Euonymous and Acer negundo ‘ Flamingo’. This creates an unstable chimera, in which reversion to green is likely, and will grow at the expense of the variegated tissues.
Monocotyledons plants produce their variegation from a linear row of cells, which, as they divide to lengthen the leaf will maintain the variegation that each started with.
Transposons are genes which can be ‘ switched’ on or off, and will cause one of two colours at any one time. They are capable of switching during the cell’s lifetime. He showed a plant with finely speckled all over variegation as an example.
Another example was a dahlia with some petals entirely white whilst the others were entirely red, due to a gene switch in relevant petals when they were composed of only one cell.
Joe explained what seeds of different variegations were capable of.
Transposons always produce seedlings with transposons.
A seed from a variegated plant will be capable of producing a seedling of the colour carried by it. Seeds carrying no chlorophyll- producing capacity may grow an embryonic root, but not a viable plant.
Joe said that in Britain and in Japan, variegated forms of wild plants could always be found.
This was our longest talk ever 2hr 10min.
Chris Davies
Indoor Meeting: Talk by Jim Payne 'Celebrating Winter'
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- Written by: Chris Davies
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9th December 2017
Jim noted that this was a small specialist nursery of 20 years standing and their catalogue was only available on their internet web “shop”, or as plants in the RHS Plantfinder.
They grew 1200 to 1500 plant varieties, including roses, and were specialists in flowering crab-apples and dogwoods.
Unusually but very usefully, Tim showed a diagram of the Earth’s movement around the Sun, showing it’s inclination, and clearly demonstrating the way sunlight falls on Earth through the seasons, because Earth’s axis is tilted towards the North Star, so tilts away and towards the Sun according to the section of it’s orbit. The angle alters the concentration of light falling on any part of the planet, giving long shadows in Winter.
Photosynthesis slows when there is less light, so leaf contents are partially reabsorbed by the plant, allowing other pigments to show through, creating the autumn tints.
Gardeners may take advantage of the leaf fall to assess the shape of trees and shrubs, with regard to pruning and training.
Jim considered four aspects of plants for the garden:- Fruit and wildlife, Bark, Flowers, and Evergreens.
He listed the qualities of a number of Crab apples, noting their attraction for Fieldfare and other birds, moving on to describe the relationship of a number of seeds to the bird species gardeners might expect to see.
Several varieties of trees, including Betula, Prunus and Acer species were recommended for their Winter bark, then Winter- flowering shrubs, finishing with the evergreen ones, a number of which were highly scented, such as Sarcococca and Chimonanthus praecox.
Jim then continued to describe the flowers of late Winter, moving into Spring, depending on the weather, including Helleborus, the small Irises, such as reticulata and its varieties, and Hepaticas.
He recommended a visit to Cambridge Botanic Gardens in Winter.
Finally, a list of Winter gardening jobs was described, with some information and reminders about our changing climate.
( See the full write-up in the next Newsletter.)
Chris Davies.
Indoor Meeting: Talk by John Massey 'Autumn into Winter'
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- Written by: Chris Davies
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11th November 2017
John gave us a wonderful, beautifully illustrated talk, strewn with his own gentle humour and a great deal of information and ideas.
John used the development and planting in his own garden to illustrate his talk.
He said that when the trees were leafless was a good time to assess their shape and required pruning. This was a time to take hard decisions, like when it was time for a tree or shrub to be removed because it was no longer enhancing the garden.He liked to juxtapose natural shapes with topiary, and trimmed holly.
Coloured bark, of silver Betula and Cornus, were complimented by evergreens, such as black- leaved Ophiopogon, Hellebores and various bulbs from late Autumn, ( Colchicums), through Winter (Galanthus).
He recommended keeping deadheads to show the effect of frost, and cutting them back when they became battered, and keeping view- lines clear, especially when use could be made of ‘borrowed landscape’.
Grasses should not be cut back until new growth comes through, and Hydrangeas should be treated with care to protect next year’s buds from frost.
Berries added to the Winter decoration, although many do not last for long. They attract birds, in his case, a flock of Waxwings, which extends interest in the garden. John recommended crab apple, Malus ‘Indian Magic’, whose fruits last well.
He said he likes to create little pictures within the garden, noting the use of evergreen ferns with snowdrops in his stumpery, and large pots, planted with Winter foliage and bulbs, with the addition of dry honesty seed pods and similar decorative items.
The first shrub to bloom after Christmas is Hammamelis, although young, newly planted specimens can be killed by frost before they are established.
John pointed out that the Japanese climate is more similar to ours than the American climate, and this could be used as a guide when choosing plants. Cloud pruning was another way of keeping shrubs under control, whilst maintaining an interesting shape.
Moving onto Spring, John said he used their idea, where gardens tend to be very small, of using the borrowed landscape as background and repeating related plants in places in order to link the garden and background.
He showed us a drift of white Fritillaria meleagris, which he said had all been brought to this part of the garden by the squirrels.
Early Alpine plants were mentioned, and then John’s recent obsession with Hepaticas. He recommended removing old leaves just before the flowers open.
He closed with a series of pictures of beautiful Hepaticas set to the background music of a Chopin Nocturne.
This was very moving as we had only recently heard of the sudden death of John’s young Head Gardener, at the age of 27, and John had mentioned his loss and shown some pictures of them together, with his family, during the talk.
Chris Davies
Indoor Meeting: Talk by John Summerfield 'Pride in the Fall'
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- Written by: Janet Stevens
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14th October 2017
This talk, held on a most summery day, concerned as you might guess all things autumn. It was billed as being a talk by John but after his introduction Gail took over the reins to guide us through their ideas on how to get the best in terms of structure and colour in the autumn garden.
John’s introduction gave a few words on their horticultural history. The arrival of a B and Q store close to their bedding plant nursery put an end to that business and in 1984 they turned their talents to establishing Westshores Nursery in N. Lincolnshire specialising in ornamental grasses and scented pelargoniums. He went on to explain that he was the builder cum maintenance person while Gail was the plant expert and botany teacher.
Gail started by talking about first flowering dates and the effects of climate change on these. She went on to give us illustrated examples of what she considered to be the “Skeleton” of an autumn garden, i.e. trees and shrubs. Amongst others she recommended species we all know such as the Japanese acers and prunus for leaf colour; spindleberry, pyracanthus, sorbus, berberis and cotoneaster for their berries. Less common (to me anyway) were eleutherococcus sieboldianus with its large black fruits resembling giant blackberries and decaisnea fargesii bearing fat blue finger-like fruits also known as Dead Man’s fingers. Her top recommendation was Abelia x grandiflora with its small glossy oval leaves and clusters of pale pink, slightly fragrant flowers lasting well into autumn.
The next selection of plants Gail called “Long term stayers” and these included grasses, verbena and asters. John interrupted the talk here to tell us about a remedy for mildew on asters meant to be a trade secret. It involved mixing up a spray solution of 1 part milk to 10 parts water. Casein, found in milk is the active ingredient for inhibiting the formation of mildew apparently. Gail added that some of the newer varieties of aster were more resistant to mildew. Other plants recommended were rudbeckias, heleniums, kniphofias, euphorbias and some of the ferns.
The third selection consisted of the plants Gail called “visitors”. These included half- hardy perennials such as fuschias and dahlias and especially salvia “Amistad” with its display of unusually deep purple flowers with almost-black calyces and stems lasting from summer through to autumn. This salvia is also extremely popular with bees and makes an excellent cut flower. Late flowering hanging baskets were easy way to add some interest and colour in the autumn.
Finally we were given advice on extending the season : making sure plants were healthy, dead heading except where seed and flower heads were to be kept for interest, and mulching were all top tips. The “Chelsea chop” was mentioned as a way of extending the season, late flowering plants also being beneficial to insects. Use of evergreens/conifers and autumn bulbs were seen as useful additions to the autumn garden.
By Janet Stevens.
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