Dogwood Tree And Shrubs
Dogwood, also known as Cornus, is a large group of plants. There We have the fiery-stemmed shrubs, as Cornus alba ‘Sibirica’ giving a lighter tone in the winter gardens, low-growing species like C. Canadensis hugging the ground at 10cm tall, and Cornus mas, the Cornelian cherry, a shrubby tree with masses of sulfur-yellow flowers in early spring.
But it’s the flowering dogwoods that are the showstoppers of the genus, putting on a dazzling show that leads the garden into summer.
“Flowering dogwoods, for the most part, are not in the least bit demanding and fill a difficult gap between spring-flowering bulbs going over and the roses and summer perennials taking off,” explains Guy Barter, chief horticulturalists at the RHS.
“It’s one of the reasons why we planted a collection of them here at Wisley about five years ago.”
They form shrubs or small to medium-sized trees, ranging between 2.5 and 8m in height,
depending on the species or cultivar.
Most are deciduous, but there’s also the evergreen C. capitata ‘Highdown’, and generally, the foliage is mid-to dark green in color, although there are variegated forms.
When planted in slightly acid soil, they’ll produce a vibrant mix of purple, red and orange leaf colour in autumn, extending their season of interest.
Some are upright and bushy, while others form a pleasing tiered structure as they mature, and over time the bark develops attractive mottled tan and grey coloring.
But it’s the blooms, which look like a mass of butterflies perched on the branches, that make these such eye-catching plants.
The flowerheads are actually made up of four or more bracts – modified leaves that act like petals – around a central cluster of tiny actual flowers.
The bracts, which sit on top of the branches, are long-lasting and generally emerge lime green, fading to cream or white before taking on shades of pink; there are also several
pink-flowered cultivars to choose from.
From the center of the bracts, strawberry-like fruit develops, which turn bright red in September.
Dogwood Fruit Edible?
They look enticing and are edible. “I have tried them,” says Guy, “but I’m sorry to say they’re rather insipid.”
Flowering dogwoods include species from North America, with C. nuttallii being the earliest to flower in April, followed by C. Florida, and those from East Asia, such as C. kousa and C. capitata, which bloom in May and June.
The Asian species and their cultivars are the easiest to grow in this country since they’re more suited to our climate.
“The kousa ones will grow in any reasonable garden soil in sun or partial shade,” says Guy. “I’ve noticed the ones at Wisley prefer a bit of shelter, and they’ll happily grow in acid to alkaline soil.
Dogwood and Soil Types
The Floridas are fussier because they prefer a more acid soil, but I suspect, as is often the case, with these things, that they’ll put up with an alkaline soil as long as it’s moist.”
The National Collection of Flowering Dogwoods is held at Newby Hall in North Yorkshire, where there’s a spectacular collection of over 100 specimens, and at Highdown Gardens in Sussex, there are flowering dogwoods happily growing on alkaline soil, which shows these
are very adaptable plants.
“We don’t grow many of the North American types at Wisley, although we do have C. nuttallii ‘Eddie’s White Wonder, which has an AGM, in an area of moist woodland – and it does well.
It’s no bigger than a large shrub, so it’s a good choice if you’re looking for something compact. As part of the main collection, we’ve also planted a group of the
Rutgers cultivars, which are spectacular,” adds Guy.
The Rutgers hybrids, such as C. x rutgersensis ‘Stellar Pink’ and the white-flowered ‘Auror,’ are the conclusive results of a breeding program set up at Rutgers University in New Jersey, the United States after native dogwoods came under attack in the 1970s from the fungal disease anthracnose and the dogwood borer beetle.
By crossing C. Florida with C. kousa, they produced the ‘Stellar’ series of cultivars that
are highly resistant to the dogwood borer and have improved resistance to both powdery mildew and anthracnose.
They’re also hardier, so they are better suited to the British climate. The same breeders also
crossed C. kousa with C. nuttallii to create ‘Venus .’“We have ‘Venus’ at Wisley, and words fail me!
It’s absolutely incredible. You can’t see the tree for blooms. Some people say it’s over the top, but I think it’s absolutely glorious,” says Guy.
‘Miss Satomi’ is another of his recommendations. “It isn’t as free-flowering as ‘Venus,’ but it’s still very floriferous and covered in deep pink flowers.
It’s smaller than other cultivars, making a good choice for small gardens and container growing. It’s bred in Japan, and our specimen at Wisley attracts so many queries that
we’ve had to put up a notice to tell them a bit more about the plant.”
Various Cultivars of Dogwood
Guy also suggests ‘Greensleeves,’ which has huge white bracts, some of the biggest
you’ll come across, which look as if handkerchiefs have blown into the tree.
They also tend to retain a greenish tint to the white blooms. For gardens in the north, Cornus kousa ‘Milky Way’ is a good option, since it will flower profusely and readily form fruit, even in cooler summers, and for something a bit different, there’s ‘Mandarin Jewel’ with its orange-colored fruit, or ‘Summer Fun,’ with variegated foliage that turns striking
shades of pink in autumn.
These versatile plants look equally as good in traditional planting schemes as they do in something more contemporary. Their elegant habit and delicate blooms make them
an ideal specimen plant for a Japanese-style garden and Guy also recommends
them as a good tree for a front garden.
Some develop a spreading canopy as they mature, so check the growth habit before buying and giving them plenty of space to develop.
For a small garden, seek out compact cultivars like ‘Nicole’ and ‘Satomi Compact,’ which will happily grow in large containers as long as the soil is kept moist.
Underplant with ferns and spring bulbs or use hardy geraniums like they do at Wisley. “The main collection at Wisley is planted in a lovely lawn area near the rose garden,” says Guy.
“It’s underplanted with camassias that flower in early May, creating a sea of blue, and the Cornus follow on from them.
We’ve also got a selection of Cornus in a woodland area where they’re combined with hydrangeas to provide continuity of color.”
Caring for Cornus
Flowering Cornus need little pruning beyond the removal of lower branches as the tree
matures to create a clear trunk. The shape of those that develop the tiered structure
can be spoilt by pruning, but the more upright, bushy types can be pruned if they’re outgrowing their space; do this in winter when the plant is dormant.
They’re generally free of pests and disease, and I don’t know of any inquiries from RHS
members about anthracnose; it’s not a problem we’ve encountered here at Wisley.
Clear weeds from under trees, especially when they’re young.
Mulching around the plant with compost is also beneficial.
Feed with a general-purpose fertilizer in February if your soil is poor – otherwise, it isn’t essential.
If you have heavy, poorly drained clay soil, it might be good to plant your tree
on a slight mound to improve the drainage.
If you’re planting Cornus in a spot where there has been honey fungus, wait for six months after you’ve removed the infected plant.
This is enough time for the fungus to die off, and it shouldn’t affect your new tree.