Rett Davis: When mowing bermuda, don't go under 2 inches

Question: Our yard is primarily bermuda grass with some fescue and weeds in it. What mower height is best?

Answer: Most home lawns are uneven, therefore bermuda grass cannot be mowed much lower than 2 inches in height without scalping some areas. Although bermuda can be cut lower, the lawn surface must be entirely flat and reel mowers become the preferred mowing equipment. A bermuda lawn that is mowed between 2-2 1/2 inches is very attractive and easy to accomplish with the standard rotary lawn mowers. Mowing frequencies will increase, especially if you have a mix of high nitrogen fertilizers and lots of rain. Mowing every 5 days is not uncommon to avoid leaving brown stems. Forget going to the gym and push that mower more often.

Question: How often should you prune Knockout roses?

Answer: Knockout roses are a bush type of rose. They can be used as a hedge or screen. I have seen hedges or specimen plants that have grown to 8 feet in height. If that is their purpose, then no pruning is needed. However, if they are planted around your home or in flower gardens, annual pruning is needed to keep them tolerable. I recommend reducing their height to within 2 feet from the ground every winter, leaving the strongest and largest canes and removing all others. By late spring a healthy Knockout will be in full bloom and almost 4 feet tall. A second but minimal pruning is needed by mid-summer to encourage a second round of heavy flower bud production. Lightly trim off all spent blooms with a pair of hedge clippers. Rosarians will cringe at this recommendation, but this is bush rose and not a good candidate for cut roses. I equate this method of pruning to a bad haircut. The difference between a bad haircut and a good one is only 2 weeks. The same can be said for pruning Knockouts. By the way, a second round of fertilizer is needed by June 1.

Question: I bought several bags of potting soil with fertilizer for my potted plants. Is there enough fertilizer in this soil to last all summer?

Answer: Do not depend on the fertilizer that is mixed with potting soil to meet all the nutritional needs of your flowers or vegetables. There is a minimal amount of fertilizer in potting soils. They are considered as "starter fertilizers" and are gone after 2-3 waterings. Warm temperatures speed up their consumption. Therefore, supplemental fertilizer is needed every 2-3 weeks. I would advise using a soluble fertilizer mixed with water. Some of the popular brands in our area are from Miracle Gro and Peters. As plants grow they need additional nutrients for flowers or vegetable production. That demand increases with age. Select soluble fertilizers with a high nitrogen content such as Miracle Gro 24-8-16 or Peters 20-20-20.

Question: We have several magnolia trees that are shedding leaves profusely and look like they are dying. What is wrong?

Answer: Magnolias took a beating this winter, especially young ones. Low winter temperatures (5 degrees) and a dry fall and early winter took a toll on them. In addition, this is the time of the year magnolias shed many of their older leaves. Therefore, the combination of the two result in a very sad looking tree. But their resiliency is legendary. In a matter of weeks new leaves will appear and warmer temperatures should bring restore their beauty.

Rett Davis is a retired Alamance County Extension Director and certified arborist. You can email your questions to him at Rett_Davis@ncsu.edu

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