Extension News

Ask the ISU Extension Garden Experts: Watering Your Plants and Cherry Leaf Spot

Note to media editors: Got gardening questions? Call the Hortline at (515) 294-3108, Monday-Friday from 10 a.m. to noon and 1 to 4:30 p.m., or e-mail us at hortline@iastate.edu. For more gardening information, visit us at Yard and Garden Online, http://www.yardandgarden.extension.iastate.edu

7/23/2009

How frequently should I water a perennial flower bed?

Many perennials perform best when they receive 1 to 1½ inches of water per week, either from rain or irrigation.

When watering, soak the soil to a depth of 8 to 10 inches. Watering frequency is largely determined by soil characteristics, weather conditions, and plant species. A thorough soaking once a week is adequate for most perennials.

Perennials, such as sedum, coreopsis, blazing star, and most ornamental grasses, possess excellent drought tolerance. Once established, these drought tolerant perennials require little or no watering.

Are there ways to reduce water use in the garden?

Apply a mulch around landscape plantings and garden areas to conserve soil moisture. Mulching reduces the rate of evaporation from the soil surface and also limits weed competition. Organic materials, such as grass clippings, straw, and shredded leaves, are excellent mulches for the vegetable garden. Wood chips and shredded bark are good choices for trees, shrubs, and perennials.

The depth of the mulch depends on the type of material used and the area. Apply wood chips and shredded bark to a depth of 3 to 4 inches around trees and shrubs. The optimum depth in the vegetable garden ranges from 2 to 3 inches for fine materials, such as grass clippings, to 6 to 8 inches for straw.

The leaves on my cherry tree have small holes in them and are turning yellow. What is the problem?

Cherry leaf spot is probably responsible for the symptoms on your cherry tree. Cherry leaf spot is caused by the fungus Blumeriella jaapii. The fungus produces small purple spots on the upper surface of the leaves. Eventually the spots turn reddish brown. After several weeks, the centers of the spots may drop out, producing a “shot-hole” appearance. Affected leaves often turn yellow and drop prematurely.

Cherry leaf spot occurs on both sour and sweet cherries in Iowa. Mild wet weather in spring creates a favorable environment for cherry leaf spot.

The cherry leaf spot fungus survives the winter on dead leaves on the ground. Spores that are released from these leaves during rainy periods in spring may infect newly emerging leaves. Raking and removing fallen leaves helps to break the disease cycle. The risk of infection can also be reduced by improving air circulation within the tree canopy with some light pruning. The application of fungicides, beginning at petal fall, is another way to control cherry leaf spot.

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Contacts :

Richard Jauron, Horticulture, (515) 294-1871, rjauron@iastate.edu

Del Marks, Extension Communications and External Relations, (515) 294-9807, delmarks@iastate.edu