Yard and Garden: Timing of Spring Lawn Care Chores

March 14, 2018, 2:52 pm | Richard Jauron, Greg Wallace

AMES, Iowa — As green color spreads across lawns, homeowners are becoming anxious to get outside. It is important to remember that spring is a sensitive time for yards – the soil is spongy, the plants are tender and the weather is unpredictable. Proper timing and gentle care will pay off as homeowners complete a few important spring tasks. Iowa State University Extension and Outreach horticulturists offer tips on spring lawn care chores. 

Tips YardWhen is the proper time to apply a pre-emergence herbicide to the lawn?  

A key to the successful control of crabgrass in lawns is the correct timing of the pre-emergence herbicide application. A pre-emergence herbicide must be applied before the crabgrass seeds germinate. If the material is applied too early, crabgrass seeds that germinate late in the season will not be controlled. If applied too late, some crabgrass seeds will have already germinated. Pre-emergence herbicides should normally be applied in early to mid-April in southern Iowa, mid-April to May 1 in central Iowa, and late April to early May in the northern portion of the state.  

Longtime residents of Iowa realize that this state’s weather is rarely “normal." Apply the pre-emergence herbicide early in the recommended time period if the weather in late March and early April is warmer than normal, late in the recommended time period if the weather is colder than normal. If still uncertain as to when to apply the pre-emergence herbicide, Mother Nature provides some helpful clues (phenological indicators). Crabgrass seed germination usually begins with the end of the forsythia bloom season or when redbud trees reach full bloom. Apply a pre-emergence herbicide when the bright yellow flowers of the forsythia begin to wither and drop to the ground or when the flower buds on redbuds begin to develop their pinkish purple color.  

When should I apply a preventive type insecticide to control white grubs in the lawn?  

White grub populations and damage to lawns vary greatly from year to year and place to place, even varying from spot to spot within the same lawn due to variations in beetle numbers, weather, turfgrass vigor, soil conditions and other factors.  

There are basically three approaches to grub management in the home lawn. One approach is to apply a preventive insecticide to the lawn on an annual basis. The second approach is to wait and see and apply a curative insecticide only when damage symptoms or signs of a grub infestation appear. The final approach is to do nothing (in regards to insecticides) and repair damaged lawn areas when grub damage occurs.  

Late June to early August is the best time to apply a preventive insecticide. Preventive insecticides available to home gardeners include imidacloprid (Bayer Advanced Season Long Grub Control and Bonide’s Annual Grub Beater) and chlorantraniliprole (Scott’s GrubEx Season Long Grub Killer). When using insecticides, carefully read and follow label directions.  

When is the best time to aerate a lawn?  

Lawns are aerated to relieve soil compaction, improve water and nutrient movement in the soil, and discourage thatch accumulation. Aeration improves the growing conditions for the turfgrass plants and results in a healthier, more vigorous lawn.  

In Iowa, April and September are the best times to aerate Kentucky bluegrass and other cool-season lawns. While the overall results are beneficial, core aeration causes some initial damage.  Aerating in April or September allows the grass to recover quickly during the favorable growing conditions in spring and early fall. When aerating the lawn in April, apply a pre-emergence herbicide after aeration to prevent the germination of crabgrass seeds.  

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