librarian2003 (librarian2003) wrote in weagardening, @ 2012-01-21 17:40:00 |
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Week 9
I'm afraid that we have had a bit of hiatus between Week 8, and now, because I'm catching up with this after the start of the spring term. However, I shall try to remember what we did!
Our plants of the week for week 9 were Crocus laevigatus from Jean, and Mahonia from Carole.
Our main topic was Shrubs for Autumn Interest. The handouts are here:
GARDENING FOR PLEASURE
Shrubs For Autumn Interest
Autumn produces some of the most vibrant colours of the year in the leaves of deciduous trees and shrubs. However, autumn colour can vary from year-to-year, and between individual trees and shrubs of the same species. While the leaves of many deciduous trees and shrubs turn red, orange or yellow in autumn, sometimes the colour can be poor even on plants noted for their autumn interest.
For most of the year, the leaf pigments that give the fiery autumn colours are masked by the green pigment chlorophyll. As the chlorophyll starts to break down just before the leaves fall, the other pigments are revealed: carotenoids and anthocyanins. Chlorophyll is responsible for the predominantly green colour of leaves, the colour arising from the absorption of blue and red light in the process of photosynthesis.
Carotenoids are mainly yellow or orange pigments, such as found in carrots, which play a secondary role in photosynthesis. Anthocyanins are red or purple pigments produced as by-products of photosynthesis. In some plants, such as copper beech, anthocyanins dominate, producing purplish-coloured leaves.
Different concentrations of these pigments causes the variation in colour – but the intensity can also be due to weather conditions and genetic differences between species and between individual plants of the same species.
Causes of poor colour
The genetic characteristics of individual trees influence the intensity of autumn colour. If an individual tree or shrub planted in good light fails to produce good autumn colour year after year, it is almost certainly a poor selection. For example, seed-raised stock will show considerable genetic variation. For this reason, selected clones that display good autumn colour, such as Nyssa sylvatica ‘Wisley Bonfire’, are propagated from cuttings or by grafting so that the colourful characteristics are retained.
Why does autumn colour vary?
Environmental conditions, as well as genetic factors, are responsible for autumn colour. In particular, the intensity of reds and purples is determined by the concentration of anthocyanins.
Anthocyanin production is favoured by:
High light levels: The reddest apples, for example, are usually those most exposed to the sun. In contrast, purple-leaved maples often become greenish when grown in deep shade.
Low temperatures: Cold, but not freezing, temperatures help to increase anthocyanins and inhibit movement of sugars out of the leaves so that more remain to be converted into pigments.
Higher rainfall: Is thought to be associated with lower levels of anthocyanins (as are high nitrogen levels), which favour conversion of surplus sugars into proteins rather than pigments.
The brilliant fall foliage colours of New England are the result of bright, dry, sunny autumn days combined with cool nights, acting on species capable of producing spectacular autumn colours, such as maples, dogwoods and American oaks. The relatively muted autumn colours in Britain are due to the generally cooler, damper, more overcast conditions. Although climate change is expected to bring warmer, drier summers to Britain, potentially leading to higher sugar levels and better autumn colours, it is not yet clear to what extent this hypothetical advantage might be cancelled out by a transition to warmer, wetter winters.
Trees for smaller gardens include: Amelanchier lamarckii; Cornus kousa var. Chinensis; various Prunus, such as P. sargentii and Sorbus ‘Joseph Rock’; Gymnocladus dioica; Stewartia pseudocamellia; Hamamelis x. Intermedia; Ginkgo biloba
Medium and large trees include: Cercidiphyllum japonicum, Nyssa sylvatica, Parrotia persica; Liquidambar styraciflua; Cladrastis lutea
Shrubs with exciting autumn tints include: Acer palmatum ‘Osakazuki’; Hamamelis; Cotinus coggygria; Berberis thunbergii; Enkianthus campanulatus; Cornus sanguinea ‘Midwinter Fire’; Ceratostigma plumbaginoides; Euonymus alata; Euonymus europaeus 'Red Cascade'; Euonymus planipes; Euonymous latifolius; Oxydendrum arboretum; Aronia arbutifolia 'Erecta'; Disanthus cercidifolius; Fothergilla major; Fothergilla gardenia; Hydrangea quercifolia; Itea virginica; Nandina domestica; Osmanthus; Photinia villosa; Stephanandra; Viburnum opulus
Callicarpa bodinieri var. giraldii has clusters of little bead-like purple berries that adorn the branches from summer, remaining there until autumn. Pyracantha coccinea has yellow red or orange berries
Vigorous climbers such as: Parthenocissus tricuspidata and Vitis coignetiae produce fiery autumn colour.
Jo Hanslip
June 2010
GARDENING FOR PLEASURE
Shrubs for Autumn Interest
This article was prepared by Guy Pullen, Nursery Manager, Clifton Nurseries, 5a Clifton Villas, London, the oldest nursery in London, in June 2007.
http://www.clifton.co.uk/pdf/Shrubs_For
Autumn is often thought of as a time for clearing out the old and preparing for the
new, but it doesn’t have to be this way! The following plants have been selected
for their stunning autumn foliage, bright berries or fine flowers and will bring a blaze
of colour, fragrance and excitement to your garden. The spectrum of interest in
autumn is vast and there are plenty of other plants that will excel - this list merely
scratches the surface and should be investigated further with your specific
conditions in mind.
FOLIAGE
Acer palmatum.
A beautiful, slow-growing, deciduous tree or shrub with ornate, palmate or finely cut leaves. Foliage turns fiery red or vibrant yellow in autumn. Prefers a shady, slightly acidic position. Heights vary.
Berberis sp, ‘Barberry’.
A genus of versatile shrubs with tough spines and stunning, bright autumn foliage. The abundant, bright red berries that follow the yellow flowers are an extra autumn
delight. Heights vary.
Cercis sp, ‘Redbud’/’Judus Tree’.
A delightful shrub or small tree that displays beautiful pink flowers on naked stems in spring and then strong autumn colour from large, heart shaped leaves. A fantastic
tree for all seasons. Eventual Height, up to 10m
Cotinus coggygria, ‘Smoke Bush’.
Bushy shrub or small tree with a pretty mass of soft pink ‘smoky’ flowers in July. The foliage ranges from mid green to deep purple before turning luminous in autumn.
Height and spread 2-3m
Euonymus alatus ‘Winged Spindle’.
This otherwise unassuming shrub provides one of the most vibrant autumn displays. The waxy green leaves turn brilliant red before littering the floor with colour. The
display comes and goes quickly, but it’s worth it for the drama. H 2m
Fothergilla sp.
An attractive, hardy shrub with conspicuous spikes of white, sweetly scented flowers in May. In autumn, the mid green leaves can turn vibrant yellow or deep-scarlet. Requires a lime-free soil in sun or partial-shade. Height 1-2m
Hamamelis sp ‘Witch Hazel’.
A small, deciduous tree with striking autumn colour, ranging from deep purple to bright yellow. In winter wispy clusters of delicately scented flowers appear on bare
stems. H 2-4m
Hydrangea quercifolia, ‘Oak Leaved Hydrangea’.
An excellent shrub with large, lobed leaves that turn from mid green to deep
bronze in Autumn. From summer to autumn large panicles of white flowers are held above the foliage. Height 2m
Itea ‘Henry’s Garnet’.
An arching deciduous shrub with dark green leaves that turn deep burgundy and orange in autumn. Creamy white, fragrant flowers are borne in summer. Prefers
slightly acidic soil and partial shade. 1-3m
Nandina domestica, ‘Heavenly Bamboo’.
An unusual, informal shrub with long, bamboo-like stems and narrow, semi-evergreen leaves that turn rich crimson through autumn and winter. New growth is flushed red and white flower spikes turn to red berries – a plant for every
season. Height 4-6ft.
Rhus typhina ‘Stag’s Horn Sumach’.
A large, suckering shrub renowned for its bright orange and red autumn colouring and furry crimson spikes of tiny fruit. The velvety new shoots are another
attraction, but not when they appear in the middle of your lawn. Height 2 - 3m
FLOWERS
Abelia x grandiflora.
An arching, evergreen shrub with small, glossy leaves and a smothering of pinky-white, tubular flowers from mid summer to autumn. Grow in full sun and good drainage, away from cold winds. Height 3m
Arbutus unedo ‘Strawberry Tree’.
A handsome, evergreen tree with bell like ivory flowers from October to December. Red balls of Strawberry-like fruits from the previous year ripen at the same time. Height 8ft.
Clifton Nurseries, 5a Clifton Villas, London W9 2PH Tel: 020 7289 6851 Fax: 020 7286 4215
Camellia sasanqua.
An unusual version of the classic evergreen shrub; sasanqua has smaller leaves than its cousin and a profusion of small pink or white flowers from mid to late Autumn. Height 3-6m
Caryopteris x clandonensis
A small, deciduous, herb-like shrub with soft, silvery, aromatic leaves and spikes of violet flowers from late summer. This delicate shrub is fully hardy, but prefers a sheltered site and good drainage. Height 1m
Ceratostigma sp. ‘Hardy Plumbago’.
Late summer brings beautiful, clear blue flowers on a bed of mid green leaves that tint red in autumn. Even the russety seed-heads catch the eye on this
popular shrub. Height 1m
Clerodendrum bungei, ‘Glory Flower’.
A deciduous, suckering shrub with dark green, toothed leaves and very fragrant cushions of small pink flowers from late summer. This unusual shrub
deserves a wider audience. H 1-2m
Elaeagnus x ebbingei.
This tough, vigorous shrub will quickly form a thick screen of silver-green leaves. Mature shrubs produce tiny, white flowers which have a sweet, heady fragrance. Height 4m
Rosa cultivars.
There is little left to say about this most popular of shrubs. Look for a modern, repeat flowering cultivar and, in a sheltered spot in London, you’ll have beautiful flowers all year.
Viburnum tinus, ‘Laurustinus’.
A solid, versatile shrub with dark evergreen leaves. Pink buds sit prettily through autumn and open to white scented flowers through winter, ovoid, metallic-blue fruits
follow. H 2.5m.
Skimmia japonica.
A short, ericaceous shrub with waxy, evergreen leaves. Spikes of tiny, tight red bud in autumn that break into fragrant, white flowers in late winter. Many varieties show red berries with the flowers.
BERRIES
Cotoneaster sp.
This tough, familiar shrub comes in many shapes and sizes, but in autumn and winter they are all covered in bright red berries. Different species can be tall, arching shrubs, wall trained, used as ground cover, etc. Feed the birds and your eyes and feel happier for it! Heights vary.
Pyracantha sp.
A spiky shrub that can be wall trained, trimmed to a hedge or left to grow wild. Summer sees a mass of white foamy flowers, but autumn brings the main attraction: Bright red, orange or yellow berries that cover the shrub from October onwards.
Callicarpa bod’ giraldii.
A deciduous shrub with mid green leaves and extraordinary pink/purple flowers in summer. Autumn brings bronze foliage and almost unreal clusters of beadlike, pink/purple berries. H 3m
Gaultheria sp.
A dense thicket of a shrub with small, spiky, glossy, leaves and large white, pink or crimson berries on the female plants. A male plant is needed to continue fruiting. This plant likes partial shade and moist, slightly acidic soil. Height 1m
Ilex sp ‘Holly’.
The humble Holly offers some of the best berries around and there are many varieties and berry colours to choose from, but not all get berries – make sure you choose one that does!
Rosa sp.
Roses have many charms but the hips are often overlooked. Species roses like rugosa and moyesii have fantastic hips, as do many of the cultivars.
Skimmia japonica subs reevesiana.
See details in ‘Flowers’ section. This subspecies has a particularly fine crop of berries.
Symphoricarpos sp Snowberry’.
A rangy, deciduous shrub with extraordinary white or pale pink berries in autumn and winter. This tough shrub is tolerant of poor, thin soil and pollution – a London
plant! Height 1-2m
Jo Hanslip
November 2011
Images for the Plants of the Week and the Autumn Interest Shrubs are all here:
Crocus laevigatus, Mahonia and Autumn Interest Shrubs
Our internet sites of the week are here:
GARDENING FOR PLEASURE
Sites of the Week : Week 9
1 For a pretty gardening blog
Laetitia Maklouf
http://laetitiamaklouf.com/
2 For a blog about urban gardening. This article is about Aztec Floating Gardens
Sidewalk Sprouts
http://sidewalksprouts.wordpress.com/hi
3 For some information on the development of Renaissance Gardens. This is an article on Wikipedia. If you haven’t already found Wikipedia, why not?
Wikipedia on Renaissance Gardens
http://en.wikipedia.org/wiki/Italian_Re
4 For information on Mediaeval Gardens, and other interesting articles
Jadwiga
http://www.gallowglass.org/jadwiga/herb
5 Want to know the secret language of flowers, and the message contained in posies? Go here:
The Language of Flowers
http://www.thegardener.btinternet.c
Jo Hanslip
November 2011
Jo