UNITED STATES—We all know what autumn is for. Planting, of course. Yes, it is a recurring theme; but there are so many different things to plant. Dormant bulbs need to get into the ground before cool and rainy winter weather. Deciduous plants that should be planted while dormant prefer an early start if planted as soon as they defoliate in autumn. Believe it or not, most evergreen plants are no different.
Evergreen plants do not experience the degree of dormancy that defoliated deciduous plants do, but they too are significantly less active during autumn and winter than they are during warmer weather. Therefore, if possible, they should also be planted in autumn, so that they can begin to slowly disperse roots through winter, to be ready to resume growth as weather warms next spring.
All planting should be planned. This is more important for trees, big shrubbery and other plants that are difficult to relocate once they have dispersed their roots. Some broadleaf evergreens that get bigger than expected can be pruned into submission. However, most coniferous evergreens are notoriously difficult to contain if they get too big for the situations into which they get planted.
‘Coniferous’ plants are those that produce cones. Cypress, pine, fir, spruce, cedar and redwood are the more familiar coniferous trees. Most coniferous trees, except for most of the various cypress, have excurrent branch structure, with lateral limbs extending from a central trunk. They cannot be pruned down without disfiguring their central trunks. Lateral limbs can be disfigured if pruned back. Such trees should therefore be planted where they can grow unobstructed to mature size.
Juniper and arborvitae are some of the more familiar of coniferous shrubbery. They can be shorn even into formal hedges, but only if shorn very regularly. Their dense foliage shades out interior foliage. If they get too big for the respective situations, they cannot be pruned back into submission without exposing their bare interiors. Once exposed, bare interior stems may never recover.
Highlight: dwarf Alberta spruce
It is so tempting to dress up a densely conical dwarf Alberta spruce, Picea glauca ‘Conica’, as a garden gnome for Halloween. They are so symmetrical that they seem to have been shorn that way. They are too small to be classified as trees, but are not as shrubby as most shrubbery either. Their practicality is rather limited to formal situations where their strict symmetry is desirable.
Dwarf Alberta spruce is very different from the straight (not dwarf) species that can get to almost 50 feet tall. It instead grows very slowly, and stays quite small, although it can eventually reach downstairs eaves. The finely textured evergreen foliage is soft, but slightly bristly. The tiny individual needles are only about half an inch long. The aroma of crushed foliage might be objectionable.
Dwarf Alberta spruce is popularly grown as a potted Christmas tree, and happens to be one of the few coniferous plants that can stay potted long enough to functions as such for a few years. In the ground, it wants rich, but well drained soil. It can rot if the soil stays too damp. Red spider mite can be a potential problem. Although it likes full sun exposure, it can get roasted in hot situations.
Horticulturist Tony Tomeo can be contacted at tonytomeo.com.