Steps you can take in the garden now will help prevent your favorite flowers from falling to disease.
Many flower and shrub diseases won't be noticeable for several more months, but there are things that can be done now to reduce disease problems. Rotate the types of flowers that are placed in pots, planting beds, etc. Continuous planting of the same species can result in carryover of certain root and foliar diseases.
Select plants adapted to the planting site and relatively free of disease problems. Certain flowers or shrubs may show resistance to specific disease problems. Use these varieties as much as possible.
Roses often suffer some cane dieback as a result of cold winter temperatures. These damaged canes are an infection point for many fungi. Prune out all damaged canes before bud break. It's still a little too early to be making these cuts now. Make the pruning cut at the node (the slight swelling of the stem) below the damaged tissue. Try to make the pruning cut at a slight angle rather than horizontal to the ground. Don't leave dead stubs on the plant. Canker fungi invade the stubs and continue to progress into healthy tissue during the summer months. Many rose cultivars require routine fungicide applications during the summer to protect against foliar diseases such as black spot. Apply fungicides at 10- to 14-day intervals.
Flowering bulbs and corms
Discard any bulbs or corms showing rotting, discoloration or insect injury before planting. Gladiolus corms may be treated with a fungicide (thiophanatemethyl, captan) to prevent Fusarium crown rot. Destroy all canna root pieces which have water-soaked buds.
Botrytis and phtophthora blights may damage plants early in the growing season. Remove and destroy all dead plant foliage before bud break. Plant peonies in well-drained soils. A soil drench of captan or Bordeaux mixture will help suppress early season diseases.
Remove old leaves and flower stalks from last year. Be sure to thin iris beds regularly in late summer by digging them up, separating them and replanting. This promotes better air circulation and prevents overcrowding. Throw out plants infested with the iris borer or that show signs of bacterial soft rot. If iris leaf spot was a problem last season, apply a fungicide (chlorothalonil, others) periodically in the spring.
Fertilizing perennial flowers
Most flowering perennials are not heavy feeders, and once established, they may not need fertilizing every year. However, if needed, apply fertilizer to perennials as growth begins in the spring. You can determine if the plant needs fertilizer by a soil test and/or by visual symptoms. Plants that are not vigorous and/or the foliage is light green or yellowish will probably benefit form a nitrogen containing fertilizer. Perennials which tend to need more fertilizer than the average perennial include astilbe, chrysanthemum, delphinium, lupines and summer phlox.
-- The garden calendar is sponsored by K-State Research and Extension-Douglas County and is written this week by County Extension Director Dennis Bejot. For more information call 843-7058 from 8 a.m.-4 p.m. Monday-Friday.