Friends don’t give friends a friendship potato

This "friendship potato" is not edible and grows into an invasive vine. (Courtesy of Beth Peck)

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This "friendship potato" is not edible and grows into an invasive vine. (Courtesy of Beth Peck)

Q: A friend was shopping for gardening supplies. He ran into a fellow from South Georgia who gave him this thing in exchange for a purple hyacinth bean plant my friend had. He called it a friendship potato and said to plant it along a fence. Do you know what it is? Beth Peck, email

A: I checked with tropical plant expert Winston Eason, who agreed with my initial guess that this is a bulbil from air potato, Dioscorea bulbifera, sometimes called tater vine. The bulbils grow from the main vine at intervals and resemble small Irish potatoes initially. They are not edible. The reason this is not a friendly gift is that the vine is terribly invasive in Florida and parts of South Georgia. A vine might drop dozens of bulbils, which are scattered by birds, chipmunks and mice. Ask your friend not to plant this. Perhaps you could give him a nice crossvine as a sercy in exchange?

Q: There is brown granular stuff dropping underneath my birch tree. It turns to brownish red mud if it gets wet. Brenda Waldrop, Conyers

A: They are probably droppings from a big population of sawflies munching on your tree’s leaves. They very much resemble caterpillars but instead are the children of the dusky birch sawfly, a wasplike insect. Since they are not caterpillars, products containing Bacillus thuringiensis won’t kill them. Imidacloprid is a systemic insecticide that can be applied to the soil around the tree in early spring before feeding activity is noticed.

Q: I read in a garden magazine that Asian dogwood berries feed monkeys but our native birds don’t eat them. If that is true, why not plug disease-resistant native dogwood cultivars instead of the kousa dogwood you recommended recently? Barbara Lewis, Marietta

A: Several native plant enthusiasts have made similar complaints. I should have given the gardener choices among the good native dogwoods. But I still love kousa dogwood, whether it is native or not. We don’t have foraging monkeys here, but I have not noticed kousa dogwood fruit piling up, uneaten, under a tree. So maybe it’s mice and chipmunks that enjoy the fruit while I enjoy the flowers.

Q: I planted Zeon zoysia about a month ago and would like to fertilize. What fertilizer should I use? Helen Griffin, email

A: Any lawn fertilizer product can be used as long as it doesn’t contain a weed control chemical. I’d apply at half strength this first time. Thereafter, you can fertilize every six weeks at the rate recommended on the bag.

Email Walter at georgiagardener@yahoo.com. Listen to his occasional garden comments on “Green and Growing with Ashley Frasca” Saturday mornings on 95.5 WSB. Visit his website, www.walterreeves.com, or join his Facebook Page at bit.ly/georgiagardener, for his latest tips.