By Nebraska Extension Horticulture Educator Kathleen Cue
Leaf scorch, also called sunscald, is the bronzing of leaf surfaces and crisping of leaf edges. Even plants that are well-adapted to our climate can be scorched. Plants have amazing resiliency, especially when Mother Nature eases them into changing seasons. But taking into consideration a spring like this one—cold and rainy—with an abrupt change to record heat, then scorched plants are to be expected.
Plants don’t have to be in the sun to suffer from scorch. Hosta, which likes and appreciates a shady location, will be scorched by high temperatures.
It’s instinctive for plant owners and gardeners to water more when plants are scorched. A key thing to remember here is that it is not the lack of water but the plant roots’ inability to take in water at the same rate the leaves are losing it that is the crux of the problem. It’s normal for plants to respond to high temperatures by letting some of the foliage die back so water uptake by the roots equals the amount of water loss from the leaves. Certainly it is important to keep the roots evenly moist, but adding water when roots are already moist puts plants at risk for root and crown fungal diseases. And it doesn’t force plant roots to take up water any faster!
Some considerations:
●Erect temporary lattice or shade cloth over newly planted perennials, shrubs and trees to minimize the sun’s burn potential.
●Mulch plants with wood chips or shredded bark to decrease water evaporation from the soil. Mulch should be 2-3 inches deep and not piled against the crown of the plant. Forget the landscaping fabric which interferes with oxygen intake at the roots.
●Always check the soil moisture before automatically watering. Push your finger past the mulch and into the soil, up to the first digit on your finger. If the root area feels moist, don’t water.
●Vegetables, trees, shrubs, fruit trees, annuals (not in containers) and perennials do best when they receive 1 inch of water each week (precipitation and irrigation combined).
●If improving the plant’s appearance is desired, use scissors to trim away the scorched parts of the leaf.
●Be mindful that fertilization and high temperatures are not compatible and can lead to greater scorching.
Mike Schomaker, Colorado State Forest Service, Bugwood.org
Ag.purdue.edu