Q: We have pink hydrangeas that haven't bloomed yet. When they do bloom we want them to stay pink. I have been advised to keep the soil alkaline. D. P. Wilbanks, email
A: If you want to do it right, start by having a soil test done (www.georgiasoiltest.com) on the area where your hydrangeas are planted. You are shooting for a soil pH of 6.0 to 6.2. At this pH, aluminum is not available to the plant. Aluminum is what enables blue flowers. If you get above 6.4 the hydrangea might have an iron deficiency. A soil pH below 7.0 is not technically alkaline soil but 6.0 - 6.2 is still the recommended pH for pink flowers. Georgia soils are typically acid. Your soil test report will give you a recommendation of how much lime to apply for raising the pH to 6.0.
You can apply a little bit more than the recommendation to bump it up another 0.10 pH. If the recommendation specifies 40 pounds per thousand square feet, you can split it into four applications per year of 10 pounds per thousand square feet (or maybe 12 pounds each time). Lime’s action in the soil gradually declines. After one year of liming, do a second soil test to see what effect the lime has had. It is probable you’ll have to apply lime every year to keep the pH in the range of 6.0 to 6.2.
Q: I recently cut down a 30-year-old wisteria vine in my backyard. Now the whole stump is covered in new growth. Is there anything I can use to stop the growth, kill the root system, etc.? Marie Fievet, Kennesaw
A: Remove the existing new growth. Then use a machete or small hatchet to chop into the top and sides of the stump. Use a foam paintbrush to dribble herbicide into the cuts. Look for a weed killer that contains both glyphosate and triclopyr as the active ingredients. Both of these chemicals inhibit resprouting but the combination is better than either one alone. That said, you'll probably see lots of root sprouts popping up many feet from the main trunk. You'll have to be persistent at removing leaves any time you see them in order to eventually starve the roots to death.
Q: Will ginseng will grow in Georgia very well? Terri Milam, email
A: Ginseng grows very well in North Georgia. That's where shady, moist, rich, well-drained sites under hardwood trees can be found. Wild-simulated ginseng production is the most profitable and ecologically sustainable means of growing ginseng. You begin by planting seed in a favorable site. Deer and slugs will be your worst enemies. You can harvest your surviving plants and their roots after about seven years, remembering that older plants are more valuable. Virginia Tech has a great guide at bit.ly/GAginseng.
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