How to seed bare spots in your yard, control insects on plants

August in the garden

I do not like blanket spray programs to control insects. In fact, I’ve only sprayed my garden once in 35 years and that was to control viburnum leaf beetle. At this point, I plan to stop treating for it and will replace the arrowwood viburnums if this insect ends up killing them. Arrowwood viburnum is a favorite target of viburnum leaf beetle, and I am sad to lose one of my favorite shrubs.

It is important to identify the insects on your plants before treating them with an insecticide to determine whether the insect really is a problem. If it is, try to assess whether the damage being done warrants control. The presence of insects feeding on the plants should not mean automatic treatment. Some insects are beneficial and help control other insects naturally. If an identified pest is causing significant damage, it is important to use the correct control with proper timing. If a variety of treatments are available, use the least toxic control possible.

Keep an eye on any plants you have installed over the last couple of years when there are dry periods. The recent heavy rains have helped, but as the summer season continues, it’s a good idea to provide supplemental water. Any plants installed this year will need regular watering during hot and dry periods for the rest of the year.

Mid-August to mid-September is a good time to seed bare spots in your lawn. Choose a seed mix that is appropriate for the amount of sun at your site. Grass grown from a mix blended for shade can look different from grass from a mix blended for sun. If your yard has adjoining areas of full sun, shade and partial shade, use a single mix of grass varieties for both sun and shade to give the lawn a more uniform appearance.

Prepare the site for seeding by removing weeds and loosening the soil. Low areas will need additional topsoil. Rake out large dirt clods, stones or debris to create a smooth seedbed. Then gently rake in the seed. Keep the soil moist. On warm days, this may require watering two or three times a day. A light layer of compost spread over the soil helps keep seeds moist.

Bluegrass takes about two weeks to germinate. It is important to keep the grass seed moist for successful germination. Watering can be scaled back to less frequent but deeper soakings as the new grass fills in.

When establishing a lawn by seed, you can expect weeds to come in before the grass can get fully established. You should mow a newly seeded lawn four times before treating with an herbicide for weeds. Pulling the weeds is also an option and can be done before mowing is necessary.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.