Ask the Master Gardener: Pinching back flowers, what potting mix to use for starting seeds
The Springfield News-Leader in Springfield, Missouri, partners with the Master Gardeners of Green County each week to bring readers a question-and-answer column with some of the expert horticulturists in the region.
Colleges and universities in the U.S. typically offer Master Gardener programs, which provide "intensive horticultural training," according to the American Horticultural Society. The certified Master Gardeners then volunteer as lecturers, researchers and gardeners in their communities. For more information about Master Gardener programs in your community, the American Horticultural Society created this page with local resources.
Here's a sample of some of the recent questions amateur gardeners had for the masters of the craft.
Some of my taller flowers last summer grew too tall and flopped over. Can I pinch these back next year to control height without losing flowers?
Most types of annual and perennial flowers can be pinched back to control growth and also to encourage more branching and more blooms. The important thing to remember is to pinch back before any flower buds started to appear, otherwise you will be removing future flowers. Certain flowers such as asters, mums, bee balm, and phlox benefit greatly from being pinched back a few times before mid-summer before bud formation is in progress. Mums and aster in particular need pinching about three times beginning in spring, stopping before July 4. Other flowers, such as campanula, cockscomb, dill, larkspur, and most sunflowers, do not benefit from this and should not be pinched back. These techniques also work for flowering shrubs that bloom most of the season, pinching back more in early and late spring will help create a thicker plant.
How late into the season to pinch these plants can be an experiment. After pinching back plants that bloom in late summer and early fall, pinch back a few others for a few weeks longer, to see what develops. Gardening is a learning process, so experiment to see what works in your garden.
What type of potting soil is best for starting seeds inside?
The best choice for seed starting indoors would be a commercially-produced, soilless mix formulated specifically for starting seeds. These mixtures are made from vermiculite and peat moss. The mixtures are sterile, lightweight, and without weed seeds. Using this type of seed-starting medium can avoid many problems with seed starting, allowing you to avoid difficulties with drainage, moisture retention, soil density, and nutrient levels.
A DIY version of a seed-starting medium can be made with equal parts of compost and topsoil, adding a bit of coarse sand. These components need to be sterilized before to avoid soil-borne pathogens. Old potting soil can also be used, but should be sterilized first. Avoid any type of soil containing fertilizer, as new seedlings do not require this.
How do I care for my potted azalea while I have it inside?
Flowering azaleas tolerate normal room temperature well, however will last longer if kept at slightly cooler temperatures, around 60-65 degrees F. The plant needs to be in a well-lighted location, however avoid direct sun. Sun directly on the flowers will cause them to fade and they won't last as long. After blooms stop, the plant can be moved to a sunny window. The soil should never be allowed to dry out completely. Watering should be done from the bottom, submerging the pot in a bucket of deep water, removing when bubbles stop rising, then allow the pot to drain before putting back in its saucer. The plant should be fertilized every two weeks with a complete, soluble liquid fertilizer. Deadheading spent flowers will help to disease problems and will also give the plant a more tidy appearance.
Readers can pose questions or get more information by calling 417-874-2963 and talking to one of the trained volunteers staffing the Master Gardener Hotline at the University of Missouri Extension Center in Greene County located inside the Botanical Center, 2400 S. Scenic Ave., Springfield, MO 65807.