Most junipers earn their reputation as bulletproof plants — right up until a section of foliage turns dull, then straw-brown, and never comes back. By the time you notice, whatever caused it has usually been at work for weeks. The good news is that junipers are honest about their troubles: where the browning starts, how quickly it spreads and what the soil feels like will point you to the cause. Work through the seven possibilities below and you will normally narrow it down within ten minutes of getting your hands dirty.
Before you water, feed or spray anything, look closely at how the damage is arranged. This one step saves a great deal of wasted effort.
One important point: junipers do not regrow from bare brown wood. Once a branch has died, it stays dead, and new growth only appears further back on living tissue. Your aim is to stop the spread, not to revive the brown itself. If you scratch the bark with a fingernail and find green beneath, that branch is still alive; dry brown under the bark means it has gone.
Drought is the most common cause in British gardens, particularly for junipers in pots and for anything planted in the last two years. Junipers are drought tolerant once established, but tolerant is not the same as immune, and a newly planted specimen has neither the roots nor the reserves to cope with a dry spell.
Needles turn dull green, then greyish, then brown and crisp. The soil is dry several centimetres down. In containers, the rootball can become hydrophobic: water runs down the inside of the pot and straight out of the drainage hole without ever wetting the middle.
Water slowly and repeatedly rather than in one quick splash. For pots, stand the container in a bucket of water until bubbles stop rising, then let it drain. Mulch the soil surface with five to eight centimetres of bark or compost, keeping it clear of the trunk. Check moisture with a finger or a bamboo cane pushed down to root depth before assuming the plant is thirsty.
The opposite problem does just as much damage, and it is harder to reverse. Junipers hate sitting wet. Heavy clay, containers without drainage holes, saucers left full of water and generous watering through a wet autumn all leave roots starved of air. Root rot organisms then move in.
Confusingly, an overwatered juniper often looks exactly like a drought-stricken one. Look for browning that creeps upwards from the base, foliage that goes limp rather than crisp, sour-smelling soil, or bark at the base that feels soft and dark. If the plant is in a pot, empty the saucer and repot into a gritty, free-draining mix. In the ground, lift and replant onto a slight mound with grit and organic matter worked into the clay. Severely affected plants rarely recover, and replacing them with something suited to a wet site is often the kinder choice.
Two fungi, Kabatina and Phomopsis, cause almost identical damage and are the classic reason for brown tips on junipers. The tips of the current season's growth die back first, working inwards from the outside of the plant. In humid spells, or after a wet spring, you may see tiny grey or black fruiting bodies on the dead needles with a hand lens.
Prune out affected tips into healthy green wood, sterilising your secateurs between cuts with methylated spirits and disposing of the prunings in the bin rather than the compost heap. Thin crowded growth to improve airflow, water the soil rather than the foliage, and water in the morning so leaves dry before night. A copper-based fungicide applied early in the season may protect new growth, but it will not cure tissue that has already browned. Easy on the nitrogen feed, too — soft, sappy growth is more susceptible.
Spider mites are barely visible to the naked eye and thrive in hot, dry conditions, especially against a south-facing wall. Their feeding causes fine stippling that pales the needles before they turn bronze or grey, and you will often see wisps of webbing in the branch crotches.
To confirm, hold a sheet of white paper under a branch and tap it firmly. Tiny specks that start to move are your answer. A strong jet of water directed at the foliage, repeated every few days, knocks back a light infestation. Horticultural oil or insecticidal soap applied in the evening, covering the undersides of the foliage thoroughly, works on heavier cases; repeat after seven to ten days to catch newly hatched mites. Keep the plant well watered, because mites target stressed junipers.
Juniper scale looks like small brown or grey bumps on the stems, so neat that it is easily mistaken for bark. These insects suck sap and leave plants yellowing, thin and prone to dieback. A black sooty mould sometimes develops on the honeydew they produce.
Prune out heavily infested branches. Light populations can be scrubbed away with a soft brush and soapy water. For stubborn infestations, apply horticultural oil in late winter or early spring before growth begins, when the vulnerable young crawlers are active, and check stem undersides carefully with a torch.
Junipers planted within the last year or two often brown without any pest or disease being involved. The causes are mundane: roots that were circling in the pot and never teased out, planting too deep so the root flare is buried, or damage from nearby digging.
Check that the base of the trunk sits at or just above soil level. Water consistently through the first two growing seasons rather than in occasional floods, and hold off feeding for the first year, since fertiliser pushes top growth while the roots are still catching up. Some dieback after moving a juniper is normal; prune it out and give the plant time.
Evergreen foliage loses moisture all winter, but frozen ground stops roots replacing it. Add drying winds and freeze-thaw cycles and you get brown, bleached patches, usually on the windward side or the side facing the midday sun. Junipers beside a road may also be scorched by salt spray.
Water thoroughly in autumn before the ground hardens, mulch well, and screen exposed specimens with horticultural fleece or a temporary windbreak. On a mild day, rinse salt from roadside foliage with a watering can. Leave winter-damaged wood in place until late spring, as buds you assume are dead may still push growth.
Nine times out of ten, a browning juniper is telling you about its roots rather than about anything you can cure with a spray. Get the water and drainage right, deal with pests promptly, and give it time — these plants are slow to complain and slow to recover, but they are worth the patience.
Photo: Peggychoucair / Pixabay
