Zonal Geranium

Zonal Geranium (Pelargonium x hortorum)

Common Geranium, Bedding Geranium

Full sun to part shade; medium moisture, well-drained; cannot tolerate waterlogged soil; pH 5.8–6.5.

12–24 inches tall and wide; blooms continuously from spring through frost with large rounded flower clusters in red, salmon, pink, white, or bicolor; circular leaf zones (darker banding) give the plant its common name; propagated vegetatively, does not produce true seed in commerce.

Propagation: tip cuttings root in 3–4 weeks at 65–70°F; overwintered as cuttings or dormant root ball in frost-free conditions; replace with new transplants each spring in Zone 6b.

Native region: Not native to Tennessee; hybrid of South African Pelargonium species.

Zonal geraniums are a Middle Tennessee staple for container plantings, window boxes, and sunny borders, but the humid summers create conditions favorable for Botrytis cinerea (gray mold), which attacks spent flower heads and stems when air circulation is poor. Remove faded flower clusters promptly and space plants to allow airflow — the single most effective disease-prevention step in Tennessee's spring and fall humidity. Watering at the base rather than overhead substantially reduces Botrytis incidence. Southern blight (Sclerotium rolfsii) can devastate in-ground plantings during hot, humid summers in poorly drained clay — raised beds or containers largely eliminate this risk. Tobacco budworm (Chloridea virescens) is the most damaging insect pest in Middle Tennessee, chewing flower buds before they open; Bacillus thuringiensis (Bt) sprays applied at first sign are effective.