QUESTION: How do I keep my beautiful zinnias from getting
powdery mildew? It may be too late for this year, but what
should I do different next year? Powdery mildew is a fungus that
thrives when nights are moderately cool and foliage stays damp.
It travels by airborne spores, and appears as gray or white
splotches on leaves, stems and flowers of susceptible plants,
such as zinnias. A mild case is merely unattractive; a severe
case of powdery mildew can cause distorted shoots and leaves,
misshapen flowers or can prevent flowering altogether. The best
defense is to give zinnias room to grow without crowding, which
allows air to circulate better around the plants, and water only
in the morning, so the foliage has time to dry before nightfall.
Cut back on the use of high-nitrogen fertilizer, which produces
succulent new growth that is a major powdery mildew magnet. Grow
them in full sun; hot temperatures (above 90 degrees) inhibit
the growth of mildew. There are fungicides available that should
be applied as soon