A few days ago a gardener proclaimed to me that an expert had told her that Lichens are found only on trees that are no longer growing. I don’t know what expert might have told her that but I’m sure she misinterpreted whatever may have been said.
The study of Lichens is a huge branch of Biology in and of itself. People who take an interest in that field of study often become quite rabid about the subject. I’ve been on expeditions where the Biologist talked as if the world existed for the sake of providing a place for Lichens to grow.
Lichens are actually a combination of two organisms, a fungus and an algae. They work together as one in order to survive in places where they couldn’t otherwise. The algae provides energy through photosynthesis while the fungus provides shelter and a place for the algae to live.
They can be found covering a wide variety of objects in addition to trees including rocks, roofs, bare soil and just about any other exposed surface.
On trees Lichens are harmless. They are actually quite attractive on trees adding an extra visual element to the landscape. Many gardeners will go to extreme lengths to get Lichens established on certain features in their garden. Lichens growing on the roof, on gravestones or other unwanted places is a whole different subject that we won’t cover here.
As for the gardener who thought that Lichens can be found only on non-growing trees, all she has to do is look in her own yard to see that Lichens are quite happy on actively growing trees.
Now that we are at the end of the summer gardening season, at lot of us will begin pulling out old and worn out plants and tossing them in the compost pile.
I found this root attached to a sweet potato plant:
Notice the knobby, bumpy nodules. This is not normal for a sweet potato root. The abnormal growth is caused by a nearly microscopic worm-like creature called a nematode.
Nematodes are the bane of sweet potato farmers in the southern states where sweet potatoes or other vegetables are grown year after year in the same spot. In addition to gnarled roots, nematodes also cause reduced yields. Often the damage shows up as black spots under the skin of the tuber that are not seen until the root is peeled leaving an unusable potato.
This nematode damage can occur on almost any common vegetable plant. If you find a root that resembles the one in the photo, destroy it and don’t attempt to compost it, otherwise you risk spreading the pests to other parts of your garden.
There is no method of control for nematodes in the garden except rotating your crops. You must rotate to a grass-related crop such as sweet corn in order to break the life cycle of the nematodes. “Regular” garden crops will support nematodes in the soil.
Knobby roots on legume plants such as peas and beans are normal and not caused by nematodes, so don’t dispose of them. Beans and peas have nodules on their roots that harbor beneficial bacteria. In this case the bacteria are beneficial to the plant and actually produce fertilizer in the form of nitrogen that the beans use to grow.
Chances are you won’t see these symptoms in a new garden because the nematodes have not had enough time to multiply.