Black Leg disease is a disease of stem cuttings where the base of the cutting turns black.
The symptoms manifest as oval, sunken, light-brown to black cankers with purple-to-black margins near the base of the stem.
The cause of Black Leg Disease is bacteria and the predisposing factors are soggy soil and overcompaction of the soil which prevents proper drainage.
Many plants can be affected by Black Leg Disease but Pelargonium cuttings are especially susceptible to the disease.
1.Remove the infected cuttings as soon as possible. Discard or burn the affected cuttings.
2.Maintain the rooting mix on the drier side whenever you are rooting stem cuttings.
3.Use loose, free-draining rooting mix to avoid soggy soil and overcompaction of the soil.