University of Maryland Extension

May Ornamental Plant Tips

zinnias
Photo: Plant zinnias directly into the garden when soil warms in spring. Germination occurs in only 4 to 7 days.

(More tips from HGIC)

  • Plant all warm-season annual plants at this time. Purchase stocky, transplants with healthy, white root systems.
  • Gently break up the roots of root-bound transplants. Summer annual bulbs like gladiolus, tuberous begonias, cannas, caladium, and dahlias can be planted now. Perennial plants can be safely divided and moved at this time.
  • This is a good time to lay down organic mulches, like pine bark, to moderate soil temperature and suppress weed growth in flower beds.
  • You may notice streaking in iris foliage caused by young iris borers. The larvae then tunnel down and feed on the rhizome. The leaves and flower stalks may wilt. The best control is prevention. Do not mulch your irises, plant rhizomes high in the planting bed and select full sun sites. If you suspect borers, dig up the rhizomes after bloom, cut off rotted and infested portions and re-plant.
  • Four-lined plant bugs are feeding on a wide range of woody and herbaceous plants, especially mint. The adults are yellowish-green with 4 black stripes. The nymphs are bright red. The bugs leave rows of small, round dark spots on leaves. Plants typically grow out of the feeding damage. 
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