Q. Can you recommend an inexpensive, low maintenance mulch to keep my vegetable garden and shrubs thriving during the heat of summer?
A. Mulches are a good way to reduce evaporation, improve water penetration, moderate soil temperature fluctuations and control weeds, among many other benefits. Organic mulches are used on a vegetable garden and can be used for flower gardens as well. Inexpensive and readily available mulches include grass clippings and dried leaves. Do not use clippings from a lawn treated with herbicides, and do apply grass clippings in thin, loose layers to reduce matting. Avoid using leaves from plants with diseases such as powdery mildew. Dried leaves don’t mat as easily as grass clippings, and because they re thin, they decompose over one season. This can be a drawback when mulching perennial plants such as shrubs. Purchased wood mulch lasts longer, and for a lower cost alternative, you can pick up shredded wood from some tree trimming companies. Apply wood mulch to depths of 3 or 4 inches to help control weeds and retain moisture around shrubs. Do not use thick layers of wood mulch that can deprive plant roots of needed oxygen.
Q: Growth of my Kentucky bluegrass lawn is starting to slow. Should I still be fertilizing?
A: It’s normal for cool-season Kentucky bluegrass, the most popular lawn grass in Colorado, to slow as daytime temperatures increase. Lawns may go dormant if there’s no rain or watering. Fertilization is generally not recommended for bluegrass during the hottest months of July and August.
The recommended amount of fertilizer for bluegrass if clippings are not collected is 2 to 4 pounds of nitrogen annually per 1,000 square feet of lawn. This means two to four fertilizer applications at the rate listed on lawn fertilizer bags and timed as follows: April, late May, late August, and early October. If applying only 2 pounds in two applications, fertilize in late May and early October. Fertilization can be paired with the two lawn core aerations recommended annually.
Q: What makes the ends of the leaves on a spider houseplant turn brown and die?
A: Leaf-tip burn is a problem common to spider plants, and is usually the result of too much fertilizer, or water that is high in soluble salts. To avoid leaf tip burn, do not allow plants to become excessively dry but don t overwater. Overwatering can deprive the roots of oxygen and lead to a buildup of salts.
When watering, allow 10 percent of what is applied to leach from the bottom of the pot, and remove any excess water from the saucer. Use a complete, soluble fertilizer for houseplants every two months if your plant is growing in an area with high light, and once every three months in medium light. Refer to the manufacturer’s recommendations to determine the appropriate amount of fertilizer to use.
Q: Late last fall, I found rust on four of my roses. I removed the roses for fear the rust would spread to all the other roses. Now I have concerns about planting new roses in the same location. Are there rust-resistant roses available?
A: Rust and powdery mildew are both fungal problems caused by water remaining on plant surfaces over an extended period or high humidity. Daytime temperatures of 65 to 70 degrees F for two to three hours provide conditions favorable for rust development.
Rose varieties resistant to these fungi are available, but there also are methods of control, including use of fungicides and removal and disposal of infected leaves and stems. Refer to the Colorado State University Cooperative Extension fact sheet 2.946, Diseases of Roses in Colorado, at www.ext.colostate.edu for details, or call the extension office in your county.
To avoid these problems, apply water at the ground level. If watering with a sprinkler, water in the mornings so plant leaves can dry more quickly than in cooler, damper evenings. Probably the best disease management method other than resistant varieties is to prune out interior crossed stems to provide better air circulation and speed surface drying.
Kevin Ritter is a Colorado State University Cooperative Extension master gardener in Denver.
