I planted 2 Juniper bushes last year and I found that they had turned brown in some places. A neighbour said it might be from winter salt. Is this so and what do I do now?
Thank-you for contacting Toronto Master Gardeners with your question.
Junipers (Juniperus ssp.) are hardy coniferous plants that can withstand adverse conditions and remain healthy. That said, junipers, like most conifers, do tend to brown out in the interior of the plant as they age. Growth is from the tips, and with little sunlight penetrating the plant, the shaded interior will die off and turn brown. Your plants are probably too young for this to be the cause of the browning and it looks like the browning includes the branch tips.
Junipers are also susceptible to salt and mechanical damage and they are prey to several diseases and pests that can cause needles to die out suddenly, even on young plants. It is difficult to make a definitive diagnosis from your photo, but your plants may be suffering from one of the following problems:
- salt damage – as your neighbour noted, road salt can cause browning on conifers if they are close to driveways or streets. You will see patches of brown in various areas on the plants.
- mechanical damage – again, your plants may have suffered from snow shovelling damage if they are near the driveway or walkways.
- overwatering – it is rare for junipers to suffer from underwatering (except in a real drought situation), but overwatering can cause the roots to rot. This will lead to browning out of the needles in patches.
- spider mites – if you can see grey webbing or tiny brown or black insects on the plants you have an infestation of spider mites. These insects suck the juices out of the needles and will eventually kill the plant.
- various fungal diseases – these can originate in the branch tips or in the roots depending on the type of fungus
The only treatment for either of the environmental conditions is to prune away the brown twigs back to the green, or if the entire branch is brown, to remove it entirely. The brown areas will never recuperate and become green again, but your plants will continue to grow well.
If you determine that the plants have spider mites, the recommended course of action is to use a powerful spray of water to dislodge and drown the insects. You will have to do this every few days for as long as 2 or 3 weeks to be sure you have eradicated the mites. Again, the brown areas will have to be pruned away. They will not grow back.
The fungal diseases will also require careful removal of the brown areas, being sure to sterilize your pruners as you go so that the disease is not spread to other areas of the plant. Fungal diseases on junipers can be difficult to combat. Watering at ground level rather than above the foliage can also reduce the spread of fungal diseases. Improved air circulation by ensuring the the plants are not crowded or congested can also help in preventing fungal attacks.
Here are a few links to useful references on diagnosing and treating juniper conditions:
https://hortnews.extension.iastate.edu/2002/5-10-2002/brownjuniper.html
https://homeguides.sfgate.com/stop-juniper-bushes-turning-brown-50466.html
https://www.redding.com/story/life/2017/07/12/master-gardeners-address-juniper-problems/472687001/
Good luck reviving your junipers!
22/05/22