Spring Pruning

Okay, Nashville’s winter has been pretty darn good. These bright sunny days are a great time to get out and do the things that need to be done. We get questions about pruning every single day at our garden center, and we want to give you some directions before you get outside with your hedge trimmers.

TWO THOUGHTS ON PRUNING:
• Know why the plant is being pruned and what your goal is before you start
• Time your pruning properly. The wrong timing will result in no flowers or fruit.

SOME REASONS FOR PRUNING:
• Train the plant to a desired form or special garden form (i.e. topiary)
• Control the plant size
• Protect people and property
• Maintain plant health
• Remove dead or dying branches
• Remove branches that rub or are starting to grow through the center mass of the plant
• Remove unwanted suckers and water sprouts
• Remove branches injured by disease or severe insect infestation
• Rejuvenate and restore old plants
• Ensure the quality of flower, foliage, and stems
• Encourage flower and fruit development
• Maintain the density of a hedge
• Delay the bloom time for landscape plantings
• Encourage a second bloom on some plants by deadheading

IMPORTANT: Keep it clean! When removing diseased wood, clean your tools after each cut by immersing cutting blades in rubbing alcohol or wiping with a Clorox wipe.

For more information on pruning hydrangeas, click here.

FAQ: Why are my azaleas' leaves turning yellowish?

Sounds like chlorosis, a disease not caused by any bug or fungus. This is an iron deficiency in our plant, the plant version of human anemia. The most common cause of iron chlorosis in azaleas is a soil that's too alkaline. Even if you've been using iron-rich fertilizer, the iron is unavailable to the plant if the soil pH is too high. This problem shows up most commonly with relatively new plantings, by the way. Big established azaleas that have survived the first few years can actually influence soil conditions favorably for themselves.

Overly wet soil can also be a cause of chlorosis in azaleas, which have shallow root systems that rot easily in heavy clay soils with inadequate drainage. Middle Tennessee has a wide variety of soils, but clay soils that are relatively alkaline are quite common, thanks to the limestone bedrock not far below us.

WHAT TO DO:
Azalea chlorosis is cured by lowering the pH of the soil using sulfur and improving drainage by adding organic material to open up tight clay soil.

Get your soil pH tested by your county Extension Agent first, so you can figure out how much sulfur to add to lower your pH to the appropriate level.

Don't use aluminum sulfate to lower soil pH for azaleas and rhododendrons as it's easy to put on toxic amounts.

FAQ: My azaleas' leaves are pale. What's wrong?

That's the handiwork of the Azalea Lace Bug. If you look on the underside of a leaf, you may see the adult of the culprit species, a 1/8" long insect with transparent wings marked with a lacy pattern in a grayish brown. The suck sap from the leaf, causing light stipple marks, and a heavy infestation will pretty much suck the color out of the leaves. If you don't see an adult, you're sure to see lots of diagnostic black dots which are either cast of skins of the larvae or excrement deposits. Evergreen azaleas are their main target, although they will attack deciduous types, too. Azaleas planted in sunny sites are victimized much more than those in shade.

HOW TO CONTROL:
Control consists of using repeated foliar sprays containing acephate, horticultural oil, a pyrethoid like bifenthrin or cyfluthrin, imidacloprid, or disulfoton. (Don't get scared by all that jargon!) The last two have a systemic action, which means they're absorbed by the leaves into the plant's system to give longer protection. Pesticide containers always list the active poison on the front label, so look there for any of these chemicals alone or in combination.

Spraying should begin in early spring when the overwintered eggs start hatching (around the first week of April is a good rule of thumb for Middle Tennessee), followed by another application about 10 days later, and then once a month or so to catch any interlopers that come in on the breeze.