What’s wrong with my mock orange?

Thanks to Jennie Ostertag for this great question and picture! In late spring 2015, she planted a mock orange, a small shrubby tree. Six months later, she noticed that some of the leaves appeared to be covered in mold or mildew.

Jennie says that she has a drip line to the plant, so the leaves don’t get wet when she irrigates, and she hadn’t gotten much rain leading up to this damage, so how could mildew have developed? Jennie also notes that the mock orange is planted in the corner of her yard, in dappled sun, so she wonders if it’s getting enough light.

After taking this picture, she trimmed off all the affected branches. But since the plant is so new, she was concerned that trimming didn’t leave a whole lot of foliage behind to support the young shrub.

Can she save it and what to do if so?

First of all, Jennie, you’ve done great detective work. Taking note of all the various environmental factors is definitely the best way to solve a plant problem and get to the best diagnosis. Location, rainfall, sunlight, planting time…all of those play a role in plant health, and taken together can actually have a synergistic effect, both positive and negative.

We reached out to Eva Van Dyke, of Barton Springs Nursery. Eva confirmed that 2015 was a hard year for gardeners, due to the monsoon-like rains. Yes, we needed and wanted the rain, but we got so much at one time and during a cool spring. Fungal spores thrived on it!

Jennie’s drip irrigation to keep water off the leaves and light situation is right on target. Eva notes that mock orange is a true understory plant, preferring no more than dappled sunlight.

With a few frosty nights, the mock orange will drop all those leaves. If cold doesn’t drop those leaves in this warm winter, do go ahead and prune back after the last frost.

Just be sure to clean away any leaf litter, and make sure to mulch heavily around the base of the plant, but not too close to the young trunk, to insulate that small root ball against the cold of its first winter in the ground.

If we have a wet winter, go ahead and remove that mulch in the spring and replace it with fresh, dry mulch, to remove any fungal spores that have been harbored over the winter.

Once the plant completely leafs out, you go ahead and do a preventative spray on the entire plant, and the soil surrounding it, with Serenade, a natural fungicide.

It’s also noteworthy from Jennie’s photos that the new growth, at the base of the plant, is entirely healthy. So it’s very likely that the older leaves are just senescing more quickly, due to transplant shock, making them more susceptible to secondary problems. I’m betting that your mock orange bounces back very quickly in its second year, Jennie, so keep us posted!