Crown rot is a disease which affects many different types of plants. Plants afflicted with this disease experience rot around their stems, in the area where the stem joins the root. Typically, crown rot is fatal, although it can be treated in some cases if a gardener is willing to put in some extensive efforts. As with many other plant diseases, prevention is easier than curing.
Several different organisms can cause crown rot. One of the most famous is Phytophthora, an organism which is often mistakenly referred to as a fungus, although it is actually a protist. These nasty garden visitors were responsible for the infamous Irish Potato Famine, and they continue to wreak havoc on plants all over the world.Fusarium fungi can also cause crown rot, as can several other fungal species, and sometimes the condition is linked to bacteria or nematodes.
The “crown” of a plant is the point at which the stem and roots join. It is a critical part of the plant's anatomy, and when a plant is attacked by crown rot, the symptoms show up very quickly. Typically, the leaves start to discolor, wither, and die off, and the whole plant may droop. Occasionally, the visible part of the stem above the ground may acquire a dark color, a slick texture, and a mushy feeling. Eventually, the plant will die off altogether, because the crown rot effectively separates the plant from its roots.
When crown rot starts to develop, the best thing to do is to discard the plant and the soil around it. If the plant is valuable or particularly beloved, treatment can be attempted by removing the plant from the soil, washing the plant and its roots, trimming away obviously dead material, and replanting it in sterile soil. Applying a fungicide may sometimes work, if a fungus is causing the crown rot. The plant should also be isolated so that it cannot infect other plants.
Prevention of crown rot starts with using good quality, sterile soil for new plantings, so that plant pathogens cannot be passed around the garden. Plants should also be given a stable supply of water which meets their needs, and gardeners should avoid over watering or allowing plants to dry out totally, as these conditions can both promote the growth of unwanted organisms in the soil. Maintaining healthy soil and keeping plants unstressed will also help to prevent crown rot and other diseases.