We planted three Sumach (Rhus typhina) trees in early 2020. Still young and just a few feet high, they have so far not produced any of their distinctive cones and have displayed none of the “autumn colour” they are famous for. They have grown alright, but a lot of their leaves are shriveled and yellowy. Online research suggests a lack of water or a terminal fungal disease are to blame. Should I just destroy them and start with something new?
Prized for its architectural growth habit, cone-shaped pollinator-friendly flowers and fiery autumnal display of blazing foliage, this hardy, deciduous plant makes a magnificent multi-stemmed specimen shrub or small tree for a sunny garden.
Typically a resilient, vigorous, easy-to-grow species, its main flaw is its flaithiúlach habit of spreading by young suckers that, even though they’re easy to cut out, automatically puts this handsome plant in some gardeners’ bad books. It’s a shame yours look so unhappy, but before considering the possibility of disease, I’d suggest first taking a good, hard look at the growing conditions to see if this is why they’ve failed to become well established.
You mention a lack of water possibly being the issue, so I’m wondering if you’ve perhaps planted them into a very dry area of the garden close to the rain shadow of established trees, shrubs, hedging or tall buildings?
Rhus typhina, or Stag’s Horn Sumach as it’s commonly known, likes a sunny spot in a moist but well-drained soil of average fertility so young plants will struggle in very dry, compacted growing conditions unless they’re regularly watered in dry weather.
Working plenty of well-rotted organic matter into the planting hole before planting would also have helped. Alternatively, is there a chance that the trees’ young root systems are hitting buried builder’s rubble, or that the plants were badly pot-bound when you bought them?
If the latter, then they may still be growing in the same restricted, pot-shaped spiral and won’t establish well without some gentle help from you to loosen out their tangled root balls.
If none of the above applies, then disease is the most likely culprit. Rhus typhina is known for being vulnerable to verticillium, a soil-borne fungal disease for which unfortunately there’s no cure.
Symptoms include weak growth and shrivelled, yellowing, dying leaves. For this reason, I wouldn’t recommend transplanting your trees into a different area of your garden because it would help to spread it.
Instead I suggest digging one up, gently loosening out the root ball and then temporarily planting it back into a large tub/container. Use a good quality John Innes compost, water well immediately after potting it on, place it in a sunny, sheltered spot, and keep it sufficiently watered in dry weather.
To help prevent the possible spread of disease, clean your tools and gardening boots etc immediately after repotting. If the repotted tree shows clear signs of recovery next spring-summer, then the problem lies in the original growing conditions. Don’t worry if it doesn’t display great autumn colour as this usually improves with age.
But if it continues to struggle , then bin or burn all three trees and replace them with a species resistant to verticillium. Examples include dogwoods (Cornus), ceanothus, hornbeam (Carpinus), malus and the katsura tree (Cercidiphyllum japonicum).