June 4, 2008
Several species of violet (Viola species) are native to Iowa. Violets usually grow in colonies and can be found in a wide variety of habitats ranging from dry, rocky prairies to moist woodlands.
Bloom on apple trees was much later than usual this spring. This was just as much due to below normal temperatures we experienced during the winter months as well as during the spring. For the buds of apple trees and other deciduous plants to emerge in the spring, the dormant buds must be exposed to so many hours of chilling to break dormancy. For apples this is typically around 1,000 hours of exposure to temperatures between 32 to 45 degrees F, but can vary from about 800 hours to over 1,200 hours.
The frequent rains this spring have created ideal conditions for the development of apple scab on crabapples. Apple scab is caused by the fungus Venturia inaequalis and is a serious problem on susceptible crabapple varieties. Scab appears on leaves as roughly circular, velvety, olive-green spots on both the upper and lower leaf surfaces. The spots eventually turn dark green to brown. Margins of these spots are feathery rather than distinct. Heavily infected leaves may curl up, become distorted in shape, turn yellow and fall off.
Diseases and Disorders
One of the familiar pests of the garden is the Colorado potato beetle, also known as the "potatobug." It's interesting to note that potatobugs were very familiar to Iowans through the fi