Autumn foliage
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On looking through my files for something to inspire me for an April article I was amazed to find that although I've written on the autumn colour of specific plants and winter colour, I haven't written about autumn foliage in general. I must have thought it too clichéd or too obvious, but when you think about it, foliage colour is what defines autumn, even though our autumns would be decidedly evergreen if it weren't for introduced plants. So it's definitely time for a photo essay on autumn foliage with something to dazzle you now and, with luck, to inspire your plantings for next year.
We're told, of course, that deciduous plants are currently unfashionable. Still, I seem to have been hearing that forever — in other words, for as long as I've heard gardeners marvel at autumn's splendour. What it really comes down to is that you can't have it both ways. Excluding a few evergreens, such as Heavenly Bamboo (Nandina domestica) and conifers that develop their winter colour early, if you want the autumn spectacle, you'll have to put up with winter's bare twigs.
But is that such a disadvantage? After all, it doesn't take much planting skill to disguise the odd deciduous specimen in a garden of evergreens, and there are plenty of deciduous plants that are really quite interesting without their leaves. Nor is that just an excuse; bark, branch structure and plant shape really do have appeal and can clearly define a plant. The common English Oak (Quercus robur), for example, is as easily recognisable from its winter outline as its summer foliage and acorns, although unlike its American cousins, it doesn't produce much in the way of autumn colour.
What are the best plants for autumn colour?
The stars of the autumn revue are so well known that they almost go without saying. Maples, oaks, liquidambar, birches, limes and ashes; their colours are legendary and rightly so. Our public parks and gardens would be very different places without them. Native plant enthusiasts may say they would be better places as well as different, but see if you can feel that way next time you stand in front of a vivid Scarlet Oak (Quercus coccinea) in the full blaze of autumn.
High up on my list of favourites are the Caucasian or Coliseum Maple (Acer cappadocicum); any of the white-barked birches (Betula), especially against a blue sky; Oriental Sweet Gum (Liquidambar orientalis), which is not as vivid as the more common L. styraciflua but offers a wider colour range; the red oaks (Q. coccinea, Q. rubra and Q. palustris); and the poplars, especially Lombardy Poplar (P. nigra var. betulifolia ‘Italica') and the Quaking Aspen (P. tremula).
There are many other trees, some less well known, with colours that warm as the weather cools. I particularly like the Snakebark Maple (Acer davidii) and its cultivars, which have beautiful white-striped green bark and subtly gradated autumn tones; Golden Rain Tree (Koelreuteria paniculata), not reliable but brilliant in the good years; Tulip tree (Liriodendron tulipifera), with interestingly shaped as well as colourful foliage; Sorrel Tree (Oxydendron arboreum), another that has its good and not-so-good years; Persian Ironwood (Parrotia persica), which has unusual witch hazel-like red flowers in late winter; and Ginkgo (Ginkgo biloba), known for many things but not always considered for its butter-yellow autumn colour.
However, those are all large trees and if your garden is a small one, you might question their suitability. In fact, most gardens have a place for at least one of these trees. Those with limited space would probably have to opt for one of the smaller Japanese Maple (A. palmatum) cultivars, but in most cases the size of the trees is not too restricting because being deciduous offers another advantage besides autumn colour — it lets in the winter light.
Sure, you may have clean up those fallen autumn leaves, which can be a chore, but there's no better compost than leaf mould. And for your efforts you not only get compost, but also a much brighter winter garden where grass can survive and you can grow shrubs and perennials beneath the trees. Evergreen trees may offer easy maintenance (though many still drop plenty of leaves), but the shade they cast often dominates the garden and makes it very hard to grow anything under them.
Slightly smaller trees include the Paperbark Maple (Acer griseum), which doesn't always colour well but has that marvellous bark; Crape Myrtle (Lagerstroemia indica), beautiful at any time; many of the flowering cherries (Prunus), with a double offering — flowers and foliage; Robinia ‘Frisia', yellow leaves all summer but really brightening in autumn; and the sumacs (Rhus and Toxicodendron), which despite suckers and possible allergic dermatitis problems, are unsurpassed for autumn red.
If you genuinely don't have room for even one of the classic autumn trees, consider large shrubs for autumn colour. Again, Japanese maples have plenty to offer, especially the Dissectum cultivars, and there are many other colourful autumn shrubs, too, often with the bonus of vivid berries. Smoke Bush (Cotinus coggygria) can develop into a small tree, but judicious trimming keeps it compact. Cotoneasters may be evergreen or deciduous. The deciduous ones can look marvellous in autumn and winter, as the berries emerge from under the coloured leaves, so don't automatically go for an evergreen. The same applies to the barberries (Berberis). Berberis wilsoniae may verge on being a noxious weed, but what a beautiful weed it can be from late March to mid May. Viburnums too, may be evergreen or deciduous, but some of the best colours occur on the semi-deciduous V. × burkwoodii. Granted, the whole shrub never colours to any great extent, but take the time to examine the individual leaves — what a magnificent range of tones, and glossy too.
Witch hazels (Hamamelis), deciduous azaleas (Rhododendron) and another near-weed, the Spindle Tree (Euonymus europaeus) all come to life in the autumn, but the ones I always wait for are the Enkianthus species. I've written before about E. perulatus, with it deep red colouration, so a word this time on E. campanulatus. Its autumn tones are more muted, but as with the comparison between the two liquidambars, the range of colours is greater and possibly applied with more subtlety. In addition, spring reveals its delicate new leaves and lily-of-the-valley flowers.
Some of the most striking red tones come not from the trees and shrubs, but from climbers, especially those in the grape family. Many old buildings are graced with such a dense covering of Boston Ivy or Virginia Creeper (Parthenocissus tricuspidata and P. quinquefolia), that it's hard to know if it's the bricks or the climber that keep the structure standing. Come autumn it doesn't really matter because however magnificent the architecture, it can't compete with flame red against a deep blue sky. The ornamental grapes, such as Tenturier Grape (Vitis vinifera ‘Purpurea') are just as colourful, and not so likely to smother your house. Take the time, too, to visit a vineyard. Bunches of ripe grapes against colouring foliage really sum up what autumn is all about.
There are even a few perennials that colour up as they die back for winter. The one I always enjoy seeing is the ornamental rhubarb (Rheum) ‘Ace of Hearts'. During the summer you could be excused for wondering why it was given that name, but come the autumn it's immediately obvious and very apt.
One of the great advantages of these plants is that apart from a very few, such as Crape Myrtle, they're all cast-iron tough. Indeed, many of them need the cold. Autumn is one of the few occasions when those of us in the cooler parts of the country can boast a little about the plants we can grow and those soft northerners can't.
What makes autumn colour?
Although we call it autumn colour, it's actually there all the while the leaves are, but we can't see it. Chemical compounds called carotenoids within the leaves, which are there all the time, cause the colours, but for the most part the green chlorophyll masks them. When the chlorophyll is withdrawn in autumn the colours become more apparent. That's why nitrogen deficiencies, which result in poor chlorophyll formation, can cause plants to develop a rather autumnal look at any time.
Carotenoids are pigments that are and essential part of the photosynthesis process. They act as light filters that capture or control particular wavelengths of light. The best autumn foliage display develops with a prolonged spell of cool but non-freezing nights followed by warm sunny days.
Japanese Maple names
When you go the buy a Japanese Maple it's not difficult to become very confused. What do all those names mean? Well, apart from the Japanese names, most of them are horticultural pseudo-Latin names for the shape and colour of the leaves. Modern cultivar names have to be in plain language, but many of the Japanese Maples pre-date the 1957 convention that made that decree. Consequently, we're left with atropurpureums, ornatums, rubrums and the like dotted all over the place.
There are five groups of Acer palmatum cultivars based on the foliage type:
Palmatum
Hand-shaped leaves with 5–7 relatively short, smooth or shallow-toothed lobes.
Elegans
Mostly 7-lobed leaves with fairly narrow lobes that can be quite deeply toothed.
Dissectum
5–9-lobed leaves in which the lobes are narrow, heavily toothed (often incised to near the midrib) and deeply cut to near the base of the leaf. Often shrubby and the most compact of the Japanese maples.
Linearilobum
5–7-lobed leaves with very narrow lobes that are deeply cut almost to the base of the leaf. The lobes are usually toothed but not deeply incised.
Variegated
As you might expect this group includes cultivars with variegated foliage, but only those not included in the other groups. For example, there is a ‘Dissectum Variegatum' that is included in the Dissectum group, not in this one.
There are many cultivars within each group and they may have other attractions, such as bark colour, growth habit and branch structure.
Other species, especially A. japonicum, are sometimes also known as Japanese maples. Less confusingly named when called the Full Moon Maple, A. japonicum is a very beautiful small tree that deserves to be more widely planted — even at the expense of some of the more common A. palmatum forms.
Copyright Geoff Bryant
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