Dwarf conifers
These small trees are big on personality, and are suitable for tight spaces, pots and bonsai, writes
Conifers are a fascinating group of ancient plants that evolved before flowering species, with cones for reproductive parts, rather than flowers. They range from towering trees, such as the redwoods, down to small, slow-growing, compact shrubs and groundcovers.
My father was a nurseryman with a passion for all conifers, but especially dwarf varieties, and he planted many as display specimens in the garden where I grew up. While they may have been classified as ‘dwarf’, they are long-lived and some of them reached quite a size over the course of 50 years.
In 1974, he donated a collection of dwarf conifers to Mount Lofty Botanic Garden in the Adelaide Hills. They were used to create the Dwarf Conifer Lawn, which is located on undulating land near the top of the Garden. The site is popular for weddings, and there is a plaque acknowledging his donation.
There are many reasons to grow these small trees. In my father's words from his 1968–69 catalogue, “Dwarf conifers can add a remarkable diversity in form and colour to any garden.”
Evergreen, with greatly varied shapes, foliage textures and colours, they provide year-round interest in gardens, which is especially welcome in winter, when deciduous plants are bare. Some change their hue during the cooler weather.
Shapes range from globes, ovals, cones and columns to irregular, architectural forms. I’m only covering some of the true dwarf conifers here, not those prostrate forms labelled as ‘groundcovers’.
what is a dwarf conifer?
A dwarf conifer is one that grows more slowly than its full-sized relatives and ends up much smaller, because the space between nodes, where the foliage occurs, is less. This dwarfing can originally occur through a genetic mutation or adaptation, then vegetative propagation by cutting or grafting ensures that the qualities of the dwarf conifer remain true.
While the definition of a dwarf conifer is unclear, expect them to reach less than 2m high in 10 years. Some of the true dwarfs may only grow to 1m over the same period.
When looking for a dwarf conifer for your garden, check the label, as this gives an indication of its expected size in 10 years under ideal growing conditions. However, don’t forget that dwarf conifers are long-lived and they don’t suddenly stop growing after 10 years. They might continue to grow at that same rate, so in 50 years they could be five times as big.
You can control their size once they get to the height you desire. Avoid all-over pruning, as the trees can take years to recover. Instead, go over the canopy once a year, and selectively trim every third or fourth shoot. Over a few years, you will have pruned the whole canopy. Don’t cut into hardwood, as they won’t reshoot at all.
CONIFERS FOR POTS AND SMALL SPACES
As many backyards get smaller and more people are living in apartments with tiny gardens and balconies, dwarf conifers are a great choice. They can be used in interesting ways – in collections, mixed among other plants, in rockeries or small gardens and in pots. They can stay in the same pot for 5–10 years, and also make great bonsai specimens.
Dwarf conifers need full sun, although in hot, dry climates you should choose a position with ambient light, such as under the canopy of a lightly foliaged deciduous tree, to avoid exposure to intense heat. Remember to water frequently and feed regularly with slow-release fertiliser.
If you're growing a dwarf conifer in a container, always use a premium potting mix and top with mulch. Ensure the pot has good drainage and don’t let the plant dry out. In a hot climate, if you notice the pot is getting hot, move it to a spot with some protection.
The best dwarf conifers for pots include Picea glauca var. albertiana ‘Conica’, Pinus mugo, and Thuja cultivars such as ‘Danica’ and ‘Hetz Midget’. There’s one out there that is perfect for your requirements. Here are some of the major groups to consider.
CEDAR
Cedrus cultivars include C. deodara ‘Mountain Beauty’, a dwarf Himalayan cedar with pale lime-green foliage and a tight, irregular bun shape. It will reach 0.5m high by 1m wide in about 15 years.
For something a bit more prostrate, try C. deodara ‘Feelin’ Blue’, with blue-green foliage, reaching up to 60cm high and 2m wide in 10 years. The original form of this species grows to 60m tall in nature.
SPRUCE
Dwarf Alberta spruce (Picea glauca var. albertiana ‘Conica’) has dense green foliage and a striking, tightly conical shape. It only grows about 10cm a year. However, P. glauca ‘Christmas Star’, which is readily available, is slightly quicker growing. They both make great living Christmas trees.
P. pungens ‘Fat Albert’ is a dwarf form of the Colorado blue spruce with dense, blue-green foliage. It has a compact pyramidal shape from early on and grows to about 2m high and wide in 10 years.
P. pungens ‘Montgomery’ also comes from the Colorado blue spruce. It has lovely blue foliage and starts as a neat bun, growing less than 1m high in 10 years. As it ages further, it can develop a leader and become more conical in shape.
JUNIPER
Juniperus communis ‘Compressa’ is a very slow-growing dwarf pencil pine with tiny, grey-green needles. It forms a tight column, reaching only 40cm in 10 years. These trees look great planted as a group, but you’ll need to be patient.
PINE
Dwarf mountain pine (Pinus mugo): Cultivars include P. mugo ‘Mops’, which forms a very slow-growing bun with dark green needles. It reaches about 50cm high by 75cm wide in 10 years.
Dwarf cultivars of eastern white pine (Pinus strobus): ‘Sea Urchin’ has dense, soft blue needles. Over a 10-year period, it forms a neat bun about 60cm high.
Dwarf cultivars of Japanese black pine (Pinus thunbergii): ‘Emery’s Dwarf’ is a rounded, compact shrub with dark green needles. It reaches about 30cm by 30cm in 10 years.
THUJA
Thuja occidentalis ‘Danica’ has glossy, emerald-green foliage arranged in flat, vertical sprays, which takes on a bronze tinge in winter. It reaches 60–70cm high and wide in 10 years.
T. occidentalis ‘Hetz Midget’ is a dense, bun-shaped conifer with light blue-green foliage packed in fan-shaped sprays. Turns a bronze-like colour in winter. Grows to 60–70cm high and wide in 10 years.
T. orientalis ‘Morgan’ is a dwarf form of the golden bookleaf pine. It has vertically arranged foliage and forms a squat, bright yellow round bun to 1m by 1m in 10 years. T. orientalis ‘Raffles’ has a similar form and shape, with slightly coarser foliage. FALSE CYPRESS
There are some great dwarf conifers among Chamaecyparis spp., best suited to a cool-temperate climate. C. obtusa ‘Kosteri’ has interesting fans of twisted green foliage and an architectural shape.
YEW
Upright Irish yew (Taxus baccata ‘Fastigiata’) has a narrow, columnar habit and dark, black-green foliage, producing bright red fruit in autumn.
This wonderful, long-lived, slow-growing plant for a pot will reach up to 2m high and 40cm wide in 10 years. It can be readily pruned to keep it to that size.
Japanese plum yew (Cephalotaxus harringtonia ‘Fastigiata’) has coarse, dark, glossy foliage and a strong vertical habit. Although it can ultimately become tall, it only grows to about 1.5m high by 40cm wide in 10 years, allowing classification as a dwarf. It's easily managed by pruning to keep it at your desired height.