Conifers / Pinaceae
The pinaceae are resinous trees found mostly in temperate regions of the Northern Hemisphere.
The leaves are linear and needle like.
The cones on the male of the species are small, terminal, or more often clustered along the stem axis, the female cones are woody and often large, consisting of many scales.
If planning propagating from seed, collect cones just as they are opening and store in a cool, dry room.
There are a number of conifer cultivars that respond well when grown as a hedge, for example;
Lawson cypress, Leyland cypress or Thuja but they can be difficult to tell apart.
Lawson's or false cypress
chamaecyparis lawsoniana has flat, scale like leaves like Leyland cypress but the drooping sprays in denser, and have resinous, musty smell.
Small red male & female cones are often borne around March.
Female cones are round and about 7mm (¼) across.
cupressocyparis leylandii foliage forms flat sprays with scale like leaves, similar to those of Lawson's cypress but more elongated and fleshier and have a citrus smell.
This is a vigorous hybrid conifer which needs cutting regularly.
Western red cedar
thuja plicata is fast growing with flat sprays of glossy, scale-like leaves, broader than those of Lawson's cypress, and has strong fruity if crushed.
Female cones are flask-shaped, to about 10mm long.
Other conifers that are sometimes used as hedges are the Monterey Cypress & Yew.
cupressus macrocarpa is salt tolerant so suited to coastal gardens, but is not hardy in colder areas.
The foliage is dense, scale like, and arranged in sprays around the branches, not flattened sprays like the Western Red Cedar, the leaves have a strong lemon scent when crushed.
taxus baccata is the traditional choice for hedging and topiary.
It has two ranks of dark green leaves with a light green underside along the length of the branches.
Females have bright red fruits.
Lawson cypress, Leyland cypress, and Western red cedar are quick growing, particularly if grown in fertile, moisture rich soil.
The downsides are that pruning twice or even three times a year is necessary to avoid excessive growth and, as they usually fail to re-sprout from old wood, they cannot be renovated by hard pruning.
In recent years lack of maintenance has been the subject of many neighbourly disputes resulting in local authorities legislating, and issuing orders to owners to keep these hedges at a stipulated height and width.
To maintain a manageable conifer hedge trim to height and width in April, June and early August preferably when the weather is cool and overcast, do not trim during hot, dry weather.
When trimming, avoid cutting into old wood.
If reducing the height of a conifer hedge this should be carried out in spring.
Remove no more than one third of the overall hedge height.
Most conifers will not re-grow from old wood, and hard pruning should be avoided.
If pruning should expose brown areas, then tie in adjacent green shoots to cover these areas.
Yew pruning requires to be done in spring and in stages e.g.
In the first year, cut back hard the top and one side only, the other side can be done the following year.
If in the first year re-growth is slow, hold back on the second year cut.
Keep hedges well watered and fed with a general fertiliser during the summer.
A 50-70mm (2”-3”) mulch of compost, bark chippings or similar will keep the roots cool, conserve moisture and prevent weeds growing.
One major drawback of conifer hedges is the formation of brown patches
Brown patches can be a result of adverse growing conditions such as drought, frost or cold, drying winds that inhibit regeneration from trimmed foliage.
Another cause is where the hedge is trimmed into old wood with limited or no capability of re-growing.
As most patches arise in late summer drought and a dry atmosphere are likely to be involved, hence as mentioned above it is best not to trim / prune during hot dry weather.
Prevention is often better than cure so general hygene and care can help to avoid this problem.
Keep the growing area free of weeds that compete for the moisture and nutrients in the growing area.
Feed with a general fertiliser70g (3oz) per sq m) in late winter and follow up with a 75mm (3") layer of organic mulch.
Dieback is another problem that has not been resolved as to whether it has been caused by disease, or a form of canker.
Fungal infection can also cause isolated dieback.
Cypress aphid can occasionally be the problem, especially early in the year, when even a few can be damaging.
Telltale signs are large grey-brown greenfly on the shoots.
The problem with this pest is, the aphids are often long gone by the time the damage is noticed.
Sometimes the only way of knowing if this was a cause is the tell tale signs of honeydew and cast skins.
If spotted in time an approved insecticide containing imidacloprid (provado) can be applied.
Cultural notes and propagation
Leyland's cypress, and many other similar conifers, may be propagated by sowing seed or taking cuttings.
Week 10: Sow the seeds thinly into a prepared seedbed or on to a tray of seed compost and place in a cold frame.
Allow the seedlings to grow on for two years then prick out into individual containers or a nursery bed.
Prick the seedling out into 70mm (3") pots of potting compost when large enough to handle, and place them in a coldframe to grow on until planting out time.
Week 26 > Take semi-ripe shoots from current season's growth 75-100mm (3"-4") long with at least 1/2" (12mm) of brownish wood at the base (heel) are ideal.
Be selective when collecting cutting material, as the shape of the cutting can determine the way the resulting plants will grow, e.g. cuttings from upright growth will produce an upright plant and if side shoots are used, a low spreading plant will be formed.
Gently pull suitable shoots from branches about halfway up the tree.
Remove bottom 38mm (1½”) of foliage.
Dip base of cuttings into a proprietary hormone rooting gel or powder before inserting them into pots or trays of well-drained compost, or directly into sandy frame soil*.
*Push the cutting into the compost until the lower leaves are touching the compost / soil.
Alternatively, root them in a garden frame or for more rapid results, place them in a propagator with bottom heat of 18°- 20°C (65°-68°F)
Lightly spray/mist them with clean water in very dry conditions but do not overdo this as cuttings will not thrive in wet conditions!
If cuttings show few signs of growth by spring, check wound area for excessive callusing which can inhibit rooting.
If so, use a sharp blade to gently scrape away some of the callus.
Cuttings should not be allowed to dry out or get too wet, shade them during hot sunny weather.
Once rooted pot up and harden off in a cold frame until they are of a size suited to planting out.
Week 38: Plant out anytime from now until April into their final quarters.
In more exposed situations support the seedlings with stakes until they become established.