Thursday, August 13, 2009
Every year, around the Fourth of July, a disease called Southern Blight appears in gardens and nurseries. And while it is not something you want to have in your garden, it one of my favorite plant pathogens. And yes, only dorks have a favorite plant pathogen.
This is how it happens: When it gets so hot outside that it hurts to breathe and we start to get afternoon thunderstorms, this fungus awakens from dormancy. It begins to grow around the bases of plants like Hosta, Ajuga, Iris, Creeping Jenny and other perennials.
As it grows, it feeds on the crowns of the plants and actually severs the stems from the roots at the soil line. You can see the white fungus on the petiole base of this Hosta leaf:
Seemingly overnight, affected plants wilt and and begin to turn brown. And if you look closely at the soil, you will see tiny spheres that look just like mustard seeds.
These "seeds" are how the fungus survives until the next summer. They hang tight-protected in their own little shells- until the days are hot and humid, causing destruction in your garden all over again.
And the worst part? The seeds can survive in the soil for up to seven years. That means you could put these seeds (they are really called sclerotia) in an envelope, file it away and in seven years disperse the sclerotia in a rival gardener's flower bed.
Since this disease is soil-borne, it is hard to manage. The best way is to remove the infected plants carefully (put them immediately in a plastic bag and do not compost) and then dig out the soil to about 1-foot deep.
If plants are growing in a nursery, there are additional tools for management of this disease- call for information.