How to remedy pesky powdery plant mildew and get that red clay ready for growing
Q: My otherwise healthy looking Brazilian verbena has suddenly developed white or light gray spots on its leaves. Am I overwatering it? – Vanessa P., Raleigh
A: Brazilian verbena (Verbena bonariensis) is certainly a low-care, drought-tolerant plant and shouldn’t need too much watering unless it is grown in a container. It sounds as though you have powdery mildew. Powdery mildew is a common fungal problem here in the warm, humid southeast, where it can attach to everything from crepe myrtles to cucumbers. A mild infection generally isn’t terribly harmful, but it will slow growth, retard flowering and fruiting and if severe enough, it can kill your plant.
Control options include commercially available fungicides or the very effective home remedy of 1 tablespoon of baking soda mixed in 1 gallon of water with a few drops of liquid dish soap. Spray all affected areas of the plant with your mixture and allow to dry before a rainfall. For a quick-growing plant like your Brazilian verbena, you can also cut back the infected plant and get rid of the affected foliage. Your plant should be back up and flowering in no time.
Q: We moved to Durham last fall from the Midwest and I am trying to learn how to plant in clay. How do I amend the soil? Do I use pine bark fines or compost? Will the roots grow outside the lovely hole I am making? – Susan, Durham
A: Carolina red clay is the bane of many a transplanted gardener’s existence, but there is an upside. Our red clay is chock full of nutrients that plants love. The secret is turning the clay into productive soil, and the answer is to add organic matter. Organic matter will help aid porosity and drainage in clay soils, or if you have sandy soils, it will help with water retention – it’s good for whatever ails you.
Good compost is probably the best material to add to your soil, but bark fines are good as well. For best results, add organic matter to your entire bed; don’t put it into that lovely hole you’ve dug. Mixing compost into a hole dug in clay will not help your plant; rather, it will create a bathtub and your plant will stay too wet after it rains. Whenever digging a hole in clay for planting, make sure to rough up the sides of the hole and have them slope from the bottom up to the surface. This will help roots escape that clay bowl and get into the surrounding soil.
Plant Spotlight
Common name: Florida anise
Botanical name: Illicium floridanum
Family: Schisandra (Schisandraceae)
Category: Evergreen shrub
Primary uses: Hedges, shade gardens.
Dimensions: 6 to 12 feet tall, but it can be pruned to stay low
Culture: Sun to part shade. Once established, Florida anise is tolerant of a wide range of conditions, from damp soils to droughty spots. It has few pest problems. In full sun, the foliage will have some yellow undertones but will be much deeper green with some afternoon shade. In heavy shade, it may be open and leggy unless pruned regularly.
General attributes: Florida anise is an evergreen shrub native to north Florida and around the gulf coast, but it is surprisingly hardy. Late-spring flowers are strappy-petalled stars in shades of red to maroon. The seed pods that follow the flowers look much like their close relative, the spice star anise. Perhaps one of its most useful characteristics is that it is exceptionally deer resistant.
This story was originally published July 28, 2017 at 11:00 AM with the headline "How to remedy pesky powdery plant mildew and get that red clay ready for growing."