Question: We were given a blue hydrangea as a gift and told it needs special soil to remain this color. What should I do?
Answer: Keep the soil acidic and you should have continuing blue hydrangea flowers. Traditional French hydrangeas, also called mopheads, come in blue, pink and colors in between. Keeping the desired color is regulated by the soil acidity. When the soil is acidic, aluminum is more available to the plant and helps make the flowers blue. If the soil is alkaline aluminum is less available and the resultant color is pink. What is sometimes noted as a grayish dishwater color is found when the soil acidity is around the neutral pH of 7.0. Have the soil in the planned planting site tested. If acidic, you do not need to make adjustments. When the soil has a pH of 6.5 or above, incorporate organic matter with the site. Also, till in soil or agricultural sulfur as instructed on the label to reduce the ground by one pH unit. Retest the soil yearly and make more adjustments if needed.
Q. Our zinnia planting looks good right now. Will they last through the summer?
A. A lack of rain during much of May has kept zinnias attractive and generally disease free. This could end as the rainy season returns. Applying a leaf spot control fungicide can help when the diseases are first noted. A simple copper fungicide can be effective but newer systemic fungicides may give better control when applied following label instructions. Some zinnia varieties are more resistant to summer diseases. Lower growing and small flowered zinnia selections, which seem to resist leaf spots, include those in the Profusion and Zahara series. These can flower through the summer. If you are a California Giant or similar zinnia fan, keep the fungicide handy or do not plant until late summer when the rains subside.
Q. I get mixed signals about using Epsom salt as a fertilizer. When should it be applied?
A. Perhaps you have heard Epsom salt it is good for tired feet and it just might be good for plants too, but it’s not a panacea. Simply it is a source of magnesium and sulfur. If your plants lack either, this foot-soaking remedy might help them too. Sulfur is usually plentiful in soils and special additions are rarely added, but magnesium could be missing. Also, some plants have a high need for magnesium including roses, gardenias, palms, peppers, tomatoes and turf. Magnesium is normally made available to turf with lime during soil acidity adjustments. Sometimes when extra magnesium-using plants show signs of yellowing or reduced vigor due to a lack of this element, the application of a magnesium product may be helpful. An occasional Epsom salt application for any planting is probably not going to be harmful as a spray or soil treatment following a product label, but neither is it likely necessary.
Q. I missed the last fertilizer time and the next one is not until October. What can I do to keep the lawn green?
A. Hopefully your last turf fertilizer application was one with slow-release properties. This could feed your lawn into the summer. Otherwise, try a minor nutrient or iron application usually permitted in most areas with restrictions during the summer months. One application may be all that is needed to give the lawn a little boost that keeps it green until the fall fertilizer feeding.
Q. I have something boring into the trunk of a large crape myrtle. It also has webs covering two of the trunks too. What is causing these problems and how should they be treated?
A. Most likely you can take this weekend off as these problems don’t sound very threatening to your crape myrtle. If the boring marks are in a row and fairly shallow, they are likely produced by a sapsucker type of bird. It’s getting some moisture from the trunk and hoping some insects get stuck in the sap too so it can feast later. Such injuries pretty much have to be tolerated. Webbing on trunks can be a bit scary too but in this case, it normally belongs to psocids, often called tree cattle. They live on bits of old bark and lichens found on the trunks and cause no harm. During the warmer months, they spin webs to conceal their young. If they become a real nuisance, the webs and insects can be washed away with a strong stream of water.
Q. Two years ago we purchased a pineapple plant with fruit which we set in the ground and then started a plant from the top. This year we have two pineapple plants with fruits. How do we know when they are ripe? Also, there is a new plant near the base of one plant. Will it produce fruit too?
A. Ripening pineapple fruits make it quite clear they are ready to harvest. First, they turn a yellow to orange color and then they give off the very familiar ready-to-eat fragrance. If your plants flowered in March, as many do after a cool winter, the fruits should be ready in August. And yes, the shoot from the base is going to produce another plant that could be in bloom and fruiting by next year.
Tom MacCubbin is an urban horticulturist emeritus with the University of Florida Cooperative Extension Service. Write him: Orlando Sentinel, P.O. Box 2833, Orlando, FL. 32802. Email: TomMac1996@aol.com. Blog with Tom at OrlandoSentinel.com/tomdigs.
