Fall Landscaper Questions

Your lawn should be left at a good height before the snow comes down. (Saklakova/Shutterstock)

Q: My landscaper told me a couple of things that I don’t understand. I think he is just trying to make some money. Is this a good time to fertilize a bluegrass lawn? Is this a good time to apply weed controls in the lawn or flower bed? How low should my lawn be mowed at the end of the year?

A: Your landscaper might be right if he is using the right fertilizer and applying it at the right time. A late fall fertilization of water-soluble nitrogen (not slow release) is good for northern lawn grasses. This could be October or November, depending on how far north you are. If the grass is still green, it is photosynthesizing, and the food produced will be stored in the crown and roots of the plant. The fertilizer will boost the food production.

These food reserves will help the plants survive the winter and then they will help the plant grow at the right rate in the early spring. Applying fertilizer in the early spring can be harmful to lawn grass because it causes the plants to grow leaves at the expense of roots. Early fertilization forces the lawn to grow leaves that need to be mowed but fall fertilization doesn’t do that. It doesn’t cause the grass leaves to grow now or in too early in spring.

The best weed control begins with preventing weeds from growing. A healthy, dense lawn and mulched flower beds reduce the need for herbicides. There are two main groups of weeds. The ones that sprout in the spring and the ones that sprout in the fall. A preemergent herbicide stops the seeds from growing. Applying a preemergent now will stop the fall weeds from sprouting and becoming big weeds next spring.

Once weeds have germinated, applying mulch is not as useful and the next best thing is hand-pulling young weeds before the roots become established. A hoe can be used on larger areas but be sure not to just move the weeds around with the hoe.

If there are larger perennial weeds, then a fall application of an herbicide can be beneficial. Perennial flowers and weeds transfer carbohydrates into the storage root, bulb, or stem tissue. If herbicides are applied, they transfer them to the storage area too. This helps kill hard-to-kill weeds. If the weeds are already dormant the weed killers won’t work, but if the temperatures are still above about 50 degrees, then follow the weed control directions and apply them soon.

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Some people believe that lawns should be left tall in the fall and others believe they should be mowed short. If the lawn is otherwise healthy, it probably doesn’t matter too much either way. Long grass leaves may insulate the grass plant crown, but the leaves may become matted down and allow disease organisms to grow under the snow. Grass mowed very short exposes the crown to the extreme cold and the mower blades may even damage the crown during the low mowing. So just mowing at the proper height all year long is probably best. Mow bluegrass between 2 to 3 inches, tall fescue 2 1/2 to 3 1/2, and Bermuda grass 1 to 2 inches tall.

(Courtesy of Jeff Rugg)