We have an approximately 20-year old circular area of pachysandra planted under a Norway maple (in midtown Toronto). For years these pachysandra seemed to be doing well, but last year, we noticed they were getting very yellow and sickly-looking. I thought it was a response to a harsh winter and hoped for improvement this year. But things look the same or worse this year. Basically, in addition to being yellow, many of the leaves are stunted, have brown areas, and in some cases, it seems the leaves have all fallen off, leaving only the stem. The stems themselves often have brown sections, sometimes close to the leaf area, sometimes close to the earth, sometimes in the middle. The brown areas may be withered and dry-seeming, they may seem slightly soggy, or, paradoxically, a combination of both. There are lots of very withered, dried stems on the ground, residue suggesting this problem has been going on for a while, without my spotting it. There are also starting to be significant blank sections in the circle – areas where the plants have presumably died off totally and shriveled up.
I have now been pulling out some of the worst looking stems, and they often pull out of the earth very easily, with no obvious root attached. It has been my habit to permit tree leaves to collect among the pachysandra, to act as mulch. During the last week, I have been trying to get rid of as much as I can of these old leaves. I have not noticed any obvious insects or other animals among the plants, with the exception of one large reddish centipede, one or two large greenish grubs or caterpillars and lots of still hibernating snails. The stem sections that have turned brown may have a knobbly texture at times, but I cannot tell if scale could be involved, or a fungus. The texture appears to be part of the stem, not something imposed on top of it.
We would like to try to save this pachysandra patch. I don’t particularly like to use chemicals, especially if I don’t know what I am fighting, but am willing to do so if required. Should I call in a professional, and if so, what kinds of services treat this type of plant? Should I try providing fertilizer and clean (commercially packaged) mulch? Would commercially packaged manure be good?
And what might be going on with these poor plants?
Thank you in advance for your help.
Thank you for contacting Toronto Master Gardeners.
Pachysandra is best grown in organically rich, medium moisture, well-drained soils in part shade to full shade. It is useful under maples, where little else grow.
Most likely the planting is suffering from volutella blight commonly called leaf blight, the most common fungal disease that affects pachysandra. This disease starts as discrete tan or brown spots that eventually merge together and kill the entire leaf. Volutella will progress from the leaves down to the stems, and as happened in your bed, large patches of pachysandra can be killed.
- It is very important to stay out of pachysandra infected with volutella blight when the foliage is wet.
- Sanitation is key. When the weather conditions are dry, remove any parts of the plant that show disease. Carefully dispose of any infected plant material including any mulch around the plant. Do not use infected plant material for composting, but discard into the garbage.
- Be sure to disinfect your pruning shears so that you do not spread the disease. Use a solution of 7 parts rubbing alcohol and 3 parts water.
- Thin the bed to promote air circulation.
- If all else fails, you may decide to utilize chemicals to help control fungus on your plants. Various chemicals are certified for use in organic gardening. Many of these organic fungicides are relatively safe for you and the environment. Carefully follow label instructions about rates, timing and method of application. Take care to ensure the proper handling of the chemical product.
- Once the area is cleared of infected plant material and the area is dry, add well-composted organic material to help add nutrients and improve the soil; this compost can be worked into the top inch or two of soil.
- Keep your Pachysandra healthy
- Avoid overhead watering. Since water favors disease development, it is best to water early in the day so the foliage dries before the cooler, nighttime temperatures that are conducive for fungal infections.
- Don’t use mulches that retain water or let autumn leaves accumulate on the plants because they, too, tend to trap water.
- Thin plants periodically during dry periods to promote good air circulation
- Adding well-composted material to your garden beds on an annual basis will help to continually improve your soil; and of course, the soil will feed your plants.
Here is an excellent article with good pictures on Volutella Blight of Pachysandra put put out by The Connecticut Agricultural Experiment Station