Juniper: Choosing One That Fits, and Keeping It Alive

Junipers have a reputation for being indestructible, and in the right place they very nearly are — poor soil, drought, wind, heat, salt, cold, neglect.

Put one in shade or in ground that stays wet and it dies slowly and unmistakably. Those are the only two things that reliably kill them, and both are decided when you plant.

Pick the form first

Juniperus covers an enormous range, and the label on the pot at the nursery is often just “juniper”. The cultivar name is what tells you the mature size and shape, and getting this wrong is the most expensive mistake available — a Skyrocket planted as a foundation shrub becomes a problem in five years.

Creeping junipers are the most useful and most under-used of these. A ‘Blue Rug’ stays ankle-high and spreads eight feet, holds a bank against erosion, needs nothing, and suppresses weeds. They are excellent tumbling over a retaining wall or through a rock garden.

Siting

• Full sun. Six hours minimum. This is not negotiable — a juniper in part shade thins, opens up, loses its colour and gradually declines, and it takes a few years to become obvious.
• Free-draining soil. Sandy, stony, poor, alkaline — all fine. Heavy clay that holds water is the problem.
• Wind, salt, heat, cold — largely irrelevant. Junipers handle exposure better than almost any other ornamental conifer.

On heavy soil, plant on a raised mound or improve drainage substantially before planting. As with rosemary, the failure mode is roots sitting wet, and it cannot be corrected afterwards.

Water and feeding

Water through the first growing season so the roots establish. After that, an established juniper needs watering only in prolonged drought.

Feed rarely or never. Junipers evolved on poor ground. A light feed in spring for a young plant is plenty; regular feeding produces soft growth that flops and is more attractive to pests.

Pruning: the dead zone rule

Junipers have a dead zone — an interior region of brown, bare stems with no green foliage and no dormant buds. Cut back into it and it stays bare permanently.

So:

• Prune only into growth that still carries green needles.
• Take small amounts, and prune in late winter or early spring.
• Shape while young. Light annual trimming keeps a plant dense and in bounds; a mature juniper that has outgrown its space usually cannot be reduced, only replaced.
• Remove dead, damaged or crossing branches at any time, cutting back to a live junction.

If you find yourself wanting to cut a juniper back by half, the honest answer is almost always that the wrong cultivar was planted, and the plant should come out.

Diagnosing problems

Berries, and a caution

The “berries” are actually fleshy cones, taking two to three years to ripen, and only female plants produce them.

Juniperus communis berries are the ones used in gin and with game, and are safe in culinary quantities. Other species vary, and some are toxic — Juniperus sabina in particular contains compounds that are genuinely harmful.

Do not eat berries from an unidentified ornamental juniper. If you want them for the kitchen, buy a plant labelled J. communis specifically.