Water management is the
main preventative measure. Frequent watering, even
in moderate to dry sites, can make conditions
favorable for development of branch blight and root
rot. Annual vinca and Vinca species are fairly
drought tolerant, so water only as needed. When
rainfall is insufficient to supply an inch of water per
week, apply deep supplemental irrigation once, or
possibly twice per week, depending on soil type,
exposure and weather conditions. Avoid excessive
amounts of fertilizer as well. To help prevent root
rot, it is also important to provide excellent
drainage. When preparing a plant bed, thoroughly
dig up the whole area. Adding organic materials,
such as composted pine bark, to the soil will help
increase drainage due to improved soil structure.