Garden tips from the Nursery Gardens - October

For the reluctant gardener, autumn comes as a relief, an end to mowing, watering and weeding.  But the keen gardener will have a list of jobs they are itching to get on with:  bulbs to plant, seeds to sow, herbaceous plants to divide, vegetables to harvest, seeds to collect, hedges needing a final trim, and so on.  Shrubs, deciduous and evergreen, are best moved in autumn so they have time to establish roots in their new positions while the soil is still warm and less likely to dry out than in spring.  For the same reasons, autumn is also the best time for tree planting. Traditionally, bare-rooted trees are dug up as soon as their leaves have dropped, and can be planted any time until the end of March, but with our increasingly uncertain seasons autumn-planted trees will do better and require less aftercare than specimens planted at the last minute.  Pot-grown trees can be planted at any time of year with appropriate care, but they too will grow away more successfully if planted in autumn.

September is a good time to be planning and choosing trees for your garden.  Leaves are beginning to develop their autumn hues, but the shape of the tree is still evident.  As autumn progresses, leaf colour intensifies before the leaves finally drop, usually by the end of November but occasionally later.  Once the green is gone and the leaves become coloured the tree is said to be fully tinted.  Autumn colour varies according to species, growing conditions and weather, and will vary every year.  The process starts as daylength shortens at the end of summer.  Reduced sunlight means the tree is unable to photosynthesise enough to feed itself so it starts to shut down for the winter and stops producing chlorophyll.  Leaf colour is provided by three pigments, chlorophyll (green), carotenes (yellow) and anthocyanins (pink and red).  Anthocyanins are also responsible for the pink and bronze shading on new leaves in spring.  During the growing season chlorophyll dominates and masks the other pigments.  As low temperatures destroy chlorophyll the green fades to yellow, but more anthocyanin is produced which increases the red colouration.  Sugars produced by the last efforts of photosynthesis on dry bright days will be concentrated, further enhancing the red colours.

We would recommend the following for reliable autumn colour:

• Crab apples – many varieties with  wide range of blossom colour from white to dark pink, and attractive fruits
• Pyrus calleriana ‘Chanticleer’ – an ornamental pear with scarlet leaves in autumn and a cloud of white blossom in spring
• Acer ‘October Glory’.  A mature specimen of this below the nursery car park always demands attention
• Sorbus ‘Autumn Spire’
• Cotoneaster rothschildianus, which has yellow berries
• Cotoneaster ‘Cornubia’ with its elegant slightly weeping habit and red berries
• Japanese maples, Acer palmatum, in variety.  Supremely elegant foliage with unsurpassable colour 
• Euonymus alatus, or spindle, with corky flanged stems and vibrant scarlet leaves
• Hamamellis, witch hazel, especially ‘Arnold Promise’ which has bands of colour on its leaves

One final suggestion is Cercidiphyllum japonicum, the Katsura tree.  It is an elegant tree with good autumn colour which curiously releases a smell of burnt sugar as the leaves change and fall.