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Autumn ignites fiery colours to finish out another season.

Like many people, perhaps gardeners in particular, I have mixed emotions about autumn. On one hand, it’s a great time of year for outdoor activities, given that daytime temperatures are pleasant and there are few insect pests to plague us. On the other hand, the rapidly shortening days are a harbinger of what’s to come—winter, with its more monochrome palette of colours.

To help satisfy a gardener’s love for colour, nature gives us a last hurrah; a spectacular show of foliar fireworks just before the outdoor gardening season shuts down to make way for the indoor pursuits of reading, tending houseplants, starting seeds, and planning next year’s garden.

A perfect autumn day is awash with colour: rich, blue skies and clear light illuminate the burnished oaks, the fiery maples, and the more subtle birches and beeches as their leaves change colour before dropping to the ground.

Not only trees change colour with the shortened days: shrubs, many perennials and grasses, and even some annuals will shift from greens to shades of gold, crimson, burgundy and copper.

If you’re like me, you choose plants to fulfill a number of tasks, including giving a good show of autumn colour.

In the July/August issue of Saltscapes, I wrote about perennials that are long- or late-blooming. This time, I’m thinking more about shrubs and trees, but of course, you should have some flowers in the mix throughout September and October. Garden mums and fall asters ignite the autumn garden with rich jewel tones, while butterfly bush (Buddleia), long-blooming roses and hydrangeas produce marvellous blooms in a rainbow of shades.

I’ve written about seedheads before, but it bears repeating—don’t be in a hurry to cut down all your perennial stalks when they’ve finished late-summer blooming. Seedheads of many types of perennials, including ornamental grasses and flowering plants such as coneflowers, black cohosh, and hostas, will withstand a lot of fall and winter weather, providing winter interest as well as a source of food for wildlife.

In recent years, more gardeners are getting hooked on versatile, easy-to-grow ornamental grasses. Many don’t bloom until late summer or early autumn, and their flowerheads will last for many weeks. Of the grasses with showy flowers, perhaps the best are the maiden or silvergrasses (Miscanthus sinensis, various cultivars). Miscanthus form a fountain of foliage, with flowerheads emerging on stalks that can reach seven feet high. The flowers last well into winter, eventually being beaten off in my windy garden, but I’ve seen gardens where the stalks still have seedheads when plants are trimmed in early spring.

Other grasses have more subtle flowers but great foliage colour—these include the panic or switch grasses (Panicum), bloodgrass (Imperata) and big and little bluestems (Andropogon and Schizachyrium).

People often think of maple trees when they think of autumn leaves, but bear in mind that native species such as sugar and red maple often give the best colour. The over-planted Norway maple has a rather poor yellow fall colour (if not covered with tarspot fungus that leaves black blotches on foliage). However, the cherished and sometimes finicky Japanese maple cultivars turn on an incredible show of foliage in hues that are almost indescribably brilliant.

Many city or suburban properties don’t have a lot of room for large trees in their gardens; a good substitute is to select shrubs, some of which can be considered small trees, that display great autumn colour.

The top shrub choices for a colourful fall display include serviceberry (Amelanchier, various species), which is native to our region and known for its early spring blooming as well as its rich autumn colour display. Sumac (Rhus) is a spreading small tree in its native form, but there are cultivars that tend not to sucker, including the popular ‘Tiger Eyes’—it has bright gold foliage during summer, then turns scarlet, orange and gold as autumn progresses. A lesser-known but equally good choice is the ‘Gro-Low’ fragrant sumac (Rhus aromatica), which has leaves similar to a miniature oak, and bright autumn colours. This variety is often used in public plantings along sidewalks in towns because it has a low, spreading growth habit.

Some of my favourite shrubs produce seeds, berries or nuts that provide another aspect of autumn interest. The humble snowberry shrub  (Symphoricarpus) is well known for its waxy white berries, which adhere to the branches long after the leaves are gone. Native Canada holly (Ilex verticillata) drops its leaves but holds on to its blazing orange or red berries until hungry songbirds devour them.

Many of the viburnums, especially the native species such as highbush cranberry and witherod, also have bright berries in red, pink, blue or black hues. For something completely different, provided you live in a spot where it’s winter-hardy, look for beautyberry (Callicarpa), which has striking amethyst-purple berries. For more recommended shrub choices, see “10 Top Shrubs to Colour your World,” opposite.

Finally, don’t forget evergreens when planning your autumn colour palette. They provide fascinating texture as well as contrasting shades of foliage that last through the winter.

Some evergreens will change colour in fall and winter, becoming brighter hued or even a totally different shade. My personal favourite is the tough-as-nails Russian cypress (Microbiota), which resembles a low-growing juniper or cedar during the summer, with medium-green foliage. Come late autumn, however, the foliage turns a unique plum to bronze, which it holds all winter. It looks especially attractive when planted near a blue spruce or cyprus, or a rich golden cedar such as ‘Sunkist.’

Why do leaves change colour anyway?

Plants contain a number of chemicals in their leaves that affect colour. For the growing months, during spring and summer, the predominant pigment is chlorophyll, which gives the leaves their green colour. Leaves gradually lose chlorophyll as the seasons progress, with the loss rate speeding up as summer gives way to fall. As the chlorophyll pigment disappears, other types of pigments become more apparent in leaves: anthocyanins, which provide red hues, and carotenoids, which produce yellow tints.

Other shades of autumn leaf colour derive from combinations of these chemicals—orange shades from carotenoids and anthocyanin, brown shades from anthocyanin and chlorophyll.

While these colour changes are taking place in leaves, a layer of corky tissue is forming where leaf stems attach to a tree branch. This abscission layer prevents the flow of nutrients from the tree roots to the leaves, and eventually the leaves drop from the plant—giving longsuffering spouses everywhere a chance to exercise their rakes, while eager gardeners without large trees gather up bagged leaves from their neighbours.

10 top shrubs to colour your world

  1. Amelanchier. Known as chuckly-pear, shadbush and serviceberry, this shrub has luminous scarlet, pink and orange fall colours.
  2. Azaleas. Some of the deciduous azaleas have fantastic autumn hues, including the Royal azalea (A. schlippenbachii), which is as brightly hued in fall as any sumac.
  3. Barberries. In autumn, their leaves explode into gold, purple, red, and orange. They also have brilliant red berries.
  4. Deciduous conifers. These are unusual conifers that drop their needles about the same time as do deciduous hardwoods. Larch (Larix) and dawn redwood (Metasequoia) are two species to look for, but be aware—they will grow into large trees over time. 
  5. Hamamelis. Native witch hazel flowers after it drops its yellow leaves. Spring flowering cultivars have red in their fall foliage. 
  6. Heaths and heathers. These low-growing beauties have colourful, evergreen foliage that changes hue as the seasons grow colder. Autumn and winter colour can include silver, gold, copper, red and even purple-black.
  7. Hydrangea. Some hydrangeas, particularly the lacecaps and paniculatas, have great foliage colour as well as handsome flowers. 
  8. Hypericum. Several shrubby types of St. John’s Wort, including ‘Albury Purple,’ produce handsome berries that may be black, red or purple; popular in cut flower bouquets.
  9. Physocarpus. In autumn, Ninebarks have bladder-like, inedible fruit and excellent foliage colour, usually purple or gold.
  10. Spirea. The gold-foliage varieties of spirea often turn a rich red before dropping their leaves. My personal favourite is the birch-leafed variety ‘Tor,’ which displays colours as brilliant as those of a sugar maple.