Fungal infection attacks landscape

Q: Our yard is showing signs of widespread fungal infection. I have lost aconites and digitalis in the past. This previous summer, the roses were stunted with black leaves and the phlox, poppies and monarda did not perform very well. Any suggestions?

A: It seems likely that more than one kind of problem is at work in your landscape. The roses have black spot, which should be addressed now with a good cleanup of all diseased foliage. Next spring and summer, regularly apply a rose fungicide.

Phlox and monarda are subject to powdery mildew, a grayish powderlike substance on the leaves and should be cleaned up now and sprayed with a fungicide that states on the label it works against powdery mildew. It is not the same fungus that causes black spot on roses. After flowering, foliage of garden poppies tends to deteriorate normally and could be cut back.

It is possible that the aconites and digitalis simply played out and had a natural death. Digitalis is a biennial that grows vegetatively for one year, then blooms and fades the next. That is likely what happened to yours. Digitalis is easy to keep going with seeds that develop in the flowers.

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Q: I have oleanders in my backyard and I was wondering what the best winter care would be. Should I cut them back?

A: Don’t cut them back. Oleanders are marginally hardy in the Charlotte area. Should there be cold damage, you will have to cut that back in late winter to green, living wood. Keeping the stems at their current length will give you some room to maneuver on this.

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Q: I have two large plumbagos in pots on my patio. How do I get them through the winter? They’re so beautiful in the summer, I don’t want to lose them. Should I cut them back and put them in my basement, or are they OK outside?

A: They are definitely not OK outside. Your plant, Plumbago auriculata, with its lovely sky blue or white flowers, is a tropical plant that originated in South Africa. You were wise to grow this plant in a pot because that means you can bring it indoors for the winter, provided the pot is not too heavy for moving. An enclosed sunroom with good light would be an excellent place so that it can slink into semi-dormancy. Water the plant occasionally though.

A well-lighted, cool, but never freezing, location would be best.