Junipers (Juniperus spp.) are evergreen plants, shrubs and trees with coniferous foliage and cones. The size of juniper shrubs can vary depending on the species, some rather low-growing and wide-spreading, yet others growing into small trees. Juniper shrubs are extremely low-maintenance, tolerating freezing temperatures, extreme heat and drought. When juniper shrubs are planted in the correct type of site, they require little to no care whatsoever. Junipers are, however, susceptible to a wide range of pests and diseases that must be treated immediately after detecting them.
Water your juniper shrub deeply to moisten the soil down to and around the roots once every one or two weeks during the first growing season after planting it. Afterward, irrigation to supplement normal rainfall isn’t necessary.
Prune your juniper shrub lightly to remove any dead, diseased or damaged growth. Avoid pruning your juniper shrub severely or shearing it, because doing so can kill the shrub.
Treat your juniper shrub for juniper webworms, which web the foliage together and turn it brown. The webworms are larval caterpillars with three pairs of legs right behind their heads. Prune away and discard infested parts of the juniper and apply the biological insecticide Bacillus thuringiensis when the larvae just hatch.
Get rid of juniper scale insects by spraying the juniper shrub with horticultural oil or applying a systemic insecticide labeled for armored scales. Juniper scales are flattened, oval-shaped immobile insects that are less than 1/8 of an inch and they feed on the shrub’s sap, causing the foliage to yellow, wilt and die back.
Treat the juniper shrub for infestations of juniper twig girdlers, which cause yellowing, browning, and then death of the smaller branches as the larvae tunnel beneath the twig bark. Juniper twig girdlers are cream-colored with brown heads in the larval stage, and shiny, brownish-black and moth-like as adults. Prune off and discard all symptomatic branches of the juniper shrub and spray the foliage with a permethrin insecticide in spring to early summer and again in late spring to midsummer.