How to maximize the size of your dahlia flowers

If you want to maximize the size of your dahlia flowers, then keep the main stems free of side shoots, allowing only the terminal bud to develop, resulting in one flower per stem. This will be most effective when growing the large dinner plate-sized cultivars. Likely the plants will need some support to prevent wind damage and the stems breaking from the weight of the flowers.

• There has been adequate rain for the most part this year to keep bluegrass lawns green and growing. Established bluegrass lawns need about an inch of water a week to continue to actively grow and stay green throughout the summer. Water deeply once a week rather than lightly multiple times a week. This promotes a deeper root system so the grass will hold up better to stress. To determine how long it takes your sprinkler to deliver 1 inch of water, set out a coffee, tuna or other shallow can with straight sides and time how long it takes to fill it with an inch of water. Be consistent with your watering practices-either water on a regular basis all summer or let your grass go dormant during hot, dry periods. If your soils are heavy and long periods of watering start to run off, then you may need to split watering into a couple times per week. Mowing your lawn at a height of 3 inches or more will also help the grass withstand stress and keep out weeds.

• If your hybrid roses have been losing their lower leaves and the remaining leaves have yellowish foliage with dark spots, then it is likely you have blackspot, which is a common fungal disease. Begin a spray program with approved fungicides immediately. The fungicides need to be applied once every 7 to 10 days, as they work to prevent the disease and do not cure what is already infected. Be sure to clean up any leaves that have fallen from the plants. Many landscape shrub roses are resistant to blackspot and do not need to be on a spray program.

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