Waiting game begins
Garden experts still have high hopes for woody, flowering shrubs
As post-freeze garden cleanup continues, we’re starting to figure out what will make it into another season. Freezedamaged branches are browning up, withered leaves are dropping and in spots here and there, new growth is emerging.
Texas A&M AgriLife Extension agents Paul Winski, a horticulture agent, and Brandi Keller, coordinator of Harris County’s master gardener program, tackled questions on trees, shrubs and other plants.
Here are their answers. If you have more questions, send them to diane.cowen@ chron.com.
Q: I have several flowering shrubs — including azaleas and Indian hawthorn — that have withered leaves. How do I care for them now?
A: Azaleas and Indian hawthorn are woody ornamental shrubs and trees, and they simply need more time to determine how much damage they have suffered, Keller said. Don’t be in a rush to prune because another cold snap could create a new injury that makes the plant susceptible to further damage.
Wait until new growth starts to appear, and let that be a guide on where exactly to cut. Ultimately, we are all in the same boat of waiting and seeing what makes it and what doesn’t. A number of factors can make outcomes vary across the area, including local
temperature, location of planting, moisture at freeze, mulch or protection, health of the plant prior to freeze and general hardiness.
Q: My oleanders look dead. Will they come back?
A: Oleanders are hardy evergreen shrubs, but temperatures below 20 degrees can cause damage to leaves and stems, Keller said. The good news is that they should regrow from the ground. Wait to prune away the damaged parts, which will likely be entire plants in this area, until after the last chance of frost in mid-March. It won’t take long for new growth to appear.
Q: I trimmed the mushy stems and leaves from my giant elephant ears that froze despite being covered. Will they come back? Is there anything else I can do for them now?
A: You took the correct steps by removing any of the mushy, damaged stems and leaves, Winski said. Your elephant ear plants should make a full recovery, since the new growth emerges from a bulb below ground. The soil had enough moisture prior to the freeze event and the ground did not freeze. Once soil temperatures begin to rise, new growth should occur.
Q: I have viburnum hedges in front of the house and along two fences in our yard. They have never frozen before but are now totally brown. I’ve scraped the stems and don’t see any green. Should they be cut way down? Is it possible they will come back?
A: Most viburnums are cold hardy and should recover, Winski said. Even with the scratch test, the best course of action still is to wait and watch for new growth. Damage to woody plants may take longer to show up, and it is possible not all branches are dead. Once new growth appears, it can be pruned above those points.
Q: My ‘Little Gem’ magnolia trees are small and have patches of something bright green on them. I thought it was fungus and have sprayed copper-based fungicides on them, but they haven’t improved. I also tried a bleachwater mix in a spray bottle, and that didn’t do anything either. Do you know what this
is and what I should do about it?
A: Your ‘Little Gem’ magnolias have lichens growing on them, Winski said. Lichens attach to bark and use it for support, but they do not negatively affect the growth of the tree.
Lichens are unique organisms in that they are a fungus and an algae working together symbiotically to survive. They produce their own food and do not remove any nutrients from the tree.
Although lichens do not cause damage, their presence can be a sign that the plant itself is in declining health due to environmental stress, such as: too much moisture, drought, planted too deep, or planted in the wrong location.
A stressed plant typically will have less foliage, resulting in more sunlight, providing a great location for lichens to grow. Trying to scrape lichens off of the bark will do more harm than good, and applying a fungicide will have no effect at all.
There is an upside to having lichens on a healthy tree: They are extremely sensitive to air pollution and are only found in places with good air quality. If your trees are healthy, enjoy the diversity that lichens add to the environment. If you think that your tree is stressed, you may want to have it evaluated by a certified arborist.
Q: My neighbor never cuts back his angel trumpet and has lush growth and abundant flowering every year. My wife cuts back ours, but it has sparse growth and little flowering. Should we prune angel trumpet or not? How can I expect it to bounce back from the freeze?
A: Angel trumpet (Brugmansia) is a woody tropical that runs the risk of being damaged or killed if the ground freezes, Keller said. Dead, hanging leaves can be cleaned up, but postpone pruning to allow rest. There is no risk in leaving a plant, but always a risk in pruning too early, especially if we have another cold spell. If you can, wait to prune until you see new growth. Scratch the bark to see if green or light cream-colored live tissue is revealed. Dead tissue is brown.
Flowering can be affected by any number of factors, such as variety, location, water and sun exposure. Angel trumpets are heavy feeders and, depending on size, could use liquid fertilizer during bloom time up to three times a week. Potted plants can get root bound every few years, which also decreases blooms.
To keep the same pot size, remove from pot, loosen soil around roots and prune to allow for new soil. Focus on pruning the thicker roots by one-half to three-quarters, but leave the thinner ones.
One last suspect is that you may be pruning it too low on the stem. Be sure you are not pruning below the stems that form a “Y.” Blooms come from above that point, so pruning lower runs the risk of it taking too long before the end of the season to sufficiently grow and form blooms.