Common Juniper

Year-round

Common juniper is a tough, low evergreen shrub that does well in the New York City area's full sun and rocky, well drained soils. It is easygoing about neglect but has one hard rule: it needs drainage, not water.

• Give it full sun and soil that drains well. It struggles and can develop root rot in heavy clay or a spot that stays wet, so this is not a plant for a low, soggy corner of the yard.
• It is naturally drought tolerant once it has a full growing season in the ground. Water new plantings deeply but infrequently rather than a little bit every day.
• Only cut into the green, living parts of the branches. Juniper wood that has already gone bare and brown will not send out new growth, so cutting back into it leaves a permanent gap in the shrub.
• In the wild here, the native form of common juniper is a low, spreading variety called Juniperus communis var. depressa. A lot of nursery plants sold simply as common juniper are instead an upright Eurasian variety that is not native to New York, so check the tag if native origin matters to you.
• The ASPCA's toxic and non-toxic plant lists for dogs and cats do not include an entry for juniper at all, so there is no confirmed pet safety rating either way. If your pet is a chewer, it is worth keeping an eye on them around it and calling your vet if they eat a noticeable amount.

Fall

Fall is common juniper's best planting window here and a good time for a light cleanup pass before winter.

• Cooler air with soil that is still warm makes fall a strong time to plant or transplant. Aim for at least six weeks before the ground freezes so roots have time to settle in.
• If needed, do a light shaping pass, still cutting only into live green wood. This is also a good time to remove old dead twigs and any branch tips that browned over summer, since clearing out that dead and infected wood is one of the most effective ways to cut down next year's disease.
• Rake up and throw away, rather than compost, any fallen needles or twig clippings that show blight symptoms. The fungi that cause it overwinter in that debris.
• Add a 2 to 3 inch layer of mulch out to the plant's drip line, keeping it pulled back a few inches from the base of the stem so moisture does not sit against it.

A tidy fall shaping keeps common juniper's low, neat form, which reads as HOA-friendly front yard structure.

Winter

Winter is when common juniper does its real work as a year round evergreen anchor, so protecting its shape matters more than active care.

• This shrub is winter hardy well beyond the New York City area's zone 7b conditions. The main risk is not cold, it is weight: junipers are multi stemmed evergreens that are especially prone to branch breakage from heavy, wet snow.
• After a heavy snow, gently brush branches upward with a broom to relieve the weight, rather than knocking down or shaking them hard. Leave ice-coated branches alone, since trying to remove ice usually snaps more than it saves.
• Hold off on any pruning until you are back into the growing season. Cold weather wood is brittle and it is hard to tell live from dead wood until new growth starts.
• Its low, blue-green, spreading form provides useful winter structure in a front yard bed without needing anything done to it at all.

Its evergreen winter silhouette holds a neat, HOA-conscious shape through the dormant season with no pruning needed.

Spring

Spring is a good time to plant common juniper here, and it is the season to watch for two things that show up on the new growth.

• If you are planting or transplanting, spring gives roots a full season to settle in before summer heat. Loosen compacted soil and mix in coarse sand or fine gravel if your soil holds water, since drainage matters more than fertilizer for this plant.
• In wet spring weather, watch for small orange, jelly-like horn-shaped growths on the branches. This is cedar-apple rust, which uses juniper as its overwintering host and needs a nearby apple or crabapple tree to complete its cycle. It rarely does serious harm to the juniper itself.
• Cool, wet spring weather is also when Phomopsis twig blight shows up, browning and killing the tips of new shoots. If you spot it, prune out the affected shoot tips and dispose of them (do not compost) before new growth fills in, since old infected wood is a major source of next year's spores.
• Skip a heavy spring fertilizer feeding. This shrub is adapted to lean soil, and pushing soft new growth with extra nitrogen makes it more vulnerable to the diseases above.

Summer

Summer care for common juniper is mostly about not overwatering it and catching hot weather pests and disease early.

• Water at the base in the early morning rather than overhead, so the foliage dries out during the day. Wet foliage sitting in humid summer air is what invites twig blight fungi to take hold.
• Warm summer weather is when Kabatina blight becomes active, killing twigs a year or older. It needs a small wound to get in, usually from insect or mite feeding, branches rubbing together, or a pruning cut, so avoid unnecessary trimming during hot, dry stretches.
• Hot, dry weather can also bring spider mites. Look for a fine, dusty stippling on the needles or light webbing between branches, and knock down a light infestation with a strong jet of water every few days.
• Do not fertilize in summer. Feeding pushes soft new growth right when disease and pest pressure is at its highest.