By Dayle Davis
Q: I bought a salvia plant a few weeks ago and have planted it into a large pot. Now the bluish-purple flowers are dried up. What’s going on? Is my salvia dying? Also, I planted large salvia plants in my garden last summer. Well, now they are even bigger. How do I split them?
A: The common name for salvia is sage. In general, this herb prefers quick-draining soil and full sunlight. If the foliage is healthy on your salvia, all is well. Salvia normally produces flowers over an extended blooming period. It sounds as though you simply need to deadhead those dried flowers to stimulate production of new flower buds. If faded blossoms are allowed to set seed, this signals the plant’s cycle is complete. Removing them helps new flowers to form.
To divide salvia, mound soil around the plants in autumn or spring, leaving just the tops uncovered. Roots will develop from the buried stems. Then you can divide the stems into sections that have roots attached and transplant them. Keep the growing tips pinched out to help stop salvia from getting too leggy.
Q: I planted a perennial Shasta daisy and “Rising Sun” tickseed beside each other this year. Both plants grew well at first, but the leaves of both now have a grayish, dusty film and the blooms have decreased noticeably. Is it mildew? What can I do about it? Also, what’s the best way to dead-head the daisy and tickseed?
A: Ah, yes, powdery mildew has made its summer appearance in your garden. Most powdery mildew fungi produce airborne spores and infect plants when temperatures are moderate — 60 to 80 degrees — and will not be present during the hottest days of the summer. Unlike most other fungi that infect plants, powdery mildew fungi do not require free water on the plant surface to germinate and infect. Some powdery mildew fungi are favored by high humidities. Overcrowding and shading keeps plants cool and promotes higher humidity. These conditions are highly conducive to powdery mildew development.
Before using fungicides, you should attempt to limit powdery mildews by other means. The following cultural practices should be beneficial for controlling powdery mildews.
Purchase only top-quality, disease-free plants of resistant cultivars and species from a reputable nursery, greenhouse or garden center.
Prune out diseased ends of woody plants, such as roses, during the normal pruning period. All dead wood should be removed and destroyed. Rake up and destroy all dead leaves that might harbor the fungus.
Maintain plants in a high vigor.
Plant properly in well-prepared and well-drained soil, where the plants will obtain all-day sun or a minimum of six hours of sunlight daily.
Space plants for good air circulation. Do not plant highly susceptible plants such as phlox, rose and zinnia in damp, shady locations.
Do not handle or work among the plants when the foliage is wet.
Water thoroughly at weekly intervals during periods of drought. The soil should be moist and 8 to 12 inches deep. Avoid overhead watering and sprinkling the foliage, especially in late afternoon or evening. Use a soil soaker hose or root feeder so the foliage is not wetted.
Generally, powdery mildew diseases do little damage to overall plant health, and yearly infections can be ignored. For example, lilacs can have powdery mildew each year, with little or no apparent effect on plant health. But on some plants, powdery mildews can result in significant damage. Thus, fungicides must be used to achieve acceptable control on the latter. For best results with fungicides, spray programs must begin as soon as mildews are detected. Spray on a regular schedule, more often during cool, damp weather. Use a good spreader-sticker with the fungicides. Be sure to cover both surfaces of all leaves with the spray.
To deadhead daisy and tickseed, pluck the blossoms off by hand, or use a handheld pruner to snip the spent stems off just above a set of leaves.
Q: I bought lisianthus at the Stan Hywet Plant sale a few weeks ago. Well, they are all wilting in their pots. Nothing I do seems to work. I kept them in full sun, but they wilted, so I moved them to part shade and that didn’t help. They are well-watered also. Why are the leaves wilting? It looks like there is a bud on them, but it hasn’t bloomed. What am I doing wrong?
A: Here I think the telling phrase is well watered. Lisianthus prefer sunny sites with fertile but well-drained soil. If yours are potted, there is a good chance they have become waterlogged. Try trimming them back by one-third, including the flower buds. Move the pots so that they receive a minimum of six hours of sunlight and do not water again until the soil feels dry when you poke your finger into the soil almost to the knuckle. Do not fertilize until the plants have recovered and produce new growth. Another slight possibility is if you have planted the lisianthus repeatedly in the same pots without changing the soil, your plants may have developed verticillium wilt. The wilt organisms usually enter the plant through young roots and then grow into and up the water-conducting vessels of the roots and stem. As the vessels are plugged and collapse, the water supply to the leaves is blocked. With a limited water supply, leaves begin to wilt on sunny days and recover at night. Wilting may first appear in the top of the plant or in the lower leaves. The process may continue until the entire plant is wilted, stunted or dead.
Dayle Davis is a freelance writer and avid perennial gardener, with a B.A. in communications and course work in botany, geology and wildflowers. Davis is certified as a Master Gardener under The Ohio State University’s Horticultural Extension. Readers can send in questions regarding lawn and garden issues, which could be featured in a future edition. Questions can be e-mailed to kcollins @leaderpublications.com, faxed to (330) 665-0908 or sent to Leader Publications, 3075 Smith Road, Suite 204, Akron, OH 44333. Please do not send any leaves, seeds or other organic material.