How to protect ornamental plants in winter

In anticipation of the colder weather to come, homeowners are beginning to think about how to protect their favorite shrubs and perennials from the lowest temperatures. The UGA publication "Winter protection of ornamental plants", by Extension horticulturist Robert Westerfield and horticulture professor Orville Lindstrom, explains that, with proper care during the rest of the year, many plants will take care of themselves.

They describe the process like this:  "During the late summer and early fall, the plants must prepare themselves for winter through a process called cold acclimation. This process is initiated by the cooler temperatures and shorter daylengths that naturally occur at this time of the year."

Proper care includes providing nutrients (through fertilizers) during active growth in warmer seasons, withholding excess nitrogen fertilizer in fall. Westerfield and Lindstrom explain:

"Fertilizing plants in the fall (after August or September) with a fertilizer high in nitrogen can cause a flush of new growth that is more susceptible to cold temperatures."

When Can I Prune My Knockout Roses?

PHOTO/UGA Horticulture Specialist Bob Westerfield

Easy-care Knockout roses provide summer-long color in many of our landscapes, but to bloom their very best a little pruning helps, and the best time for pruning in Cobb County is nearly upon us.

Clemson University's "Ask a Master Gardener" publication "Pruning Knockout Roses: When and How," says "Rose pruning should be done just as buds break dormancy...probably around late February or early March. When the buds have swelled but no new growth has yet appeared, it is the ideal time to prune bush or shrub type roses."

North Carolina State University (NCSU) Extension's "Pruning Knock Out Roses" agrees with that timing, saying "Rose pruning should be done just as buds break dormancy, usually around mid-to-late February or early March in Zone 7. A good rule of thumb to help you remember is 'prune your roses when the forsythia is in bloom.'"

NCSU's instructions include the qualifiers, to wait until the second and possibly even the third year of growth before pruning, and that some shaping and thinning can be done in the summer, if needed. This summer thinning is especially useful to eliminate any points of contact where branches touch or rub against each other, to reduce spots where disease might enter the plant.

Clemson's publication explains the best method of figuring out where on the cane to make a pruning cut:

"Prune the bush to make it more open in the center. This will increase air circulation and help prevent diseases. Since rose bushes send out new growth from the bud just below a pruning cut, try to make pruning cuts above a leaf bud facing out from the center of the plant. Make a cut 1/4 inch above the bud and angled at the same angle as the bud."

UGA's Georgia FACES article "Prune Roses Now for More Blooms Later," by UGA Extension's Frank Watson, adds an emphasis on checking the pith, or center, of the stem after it's been cut. If the center is creamy white or greenish, then the stem is healthy, but if it is brown or black, Watson recommends "continu[ing] to cut down the cane until green or white pith is revealed. In some cases this may mean a drastic reduction of the cane. Occasionally, the pith will become darker with each successive cut, and the cane will have to be removed at the bud union using a small pruning saw."

For further information, read the complete articles at the links as they appear above.

For those who have not planted Knockout roses, but who are planning to, the UGA publication "Roses in Georgia, Selecting and Growing Techniques," by Horticulturists Bob Westerfield and Malgorzata Florkowski and Technical Assistant Adrianne Todd, provides a clear and easy-to-follow description of how to plant and care for your new roses, to promote abundant bloom.

Figs Slow to Leaf Out?

We've had a lot of calls to the office recently about figs that still have put out no, or few, new leaves. We did have some unusually cold weather this past winter, and UGA's publication "Home Garden Figs" contains this caution about the relative cold-hardiness of figs in Georgia:

"There are many varieties of figs available, but only a few are well adapted to Georgia. If you want to try to grow figs in the mountains, select a protected site and try Celeste or Hardy Chicago. In addition, some varieties such as Brown Turkey will produce some figs on the current season’s growth after being killed to the ground by a freeze."

A Texas A&M webpage that contains Fig FAQs includes this statement:

"Normally we prune figs very little in Texas because of potential cold damage, ie. we usually have to prune back to live wood. This past year our varieties went dormant extremely well. We had a lot of cool, mild days prior to very hard winter freezes. The figs went through this very well and most were in great shape. Then we warmed up in February and the plants lost some of their accliminated dormancy and bam, they froze to the ground in March."

North Carolina State University's Charlotte Glen has this to add:

"The only other problem figs sometimes experience in our area is cold damage. This is more common in particularly cold winters or when extremely cold temperatures follow a stretch of unseasonably mild weather in late winter. It is very rare for figs to be killed completely, though they may have to be cut back to the ground and allowed to re-grow if heavily damaged. Cold damage can be minimized by planting fig bushes against a south facing wall."

The figs in Cobb County have been very slow to leaf out primarily because of the hard freezes that we experienced this winter. Some plants will have been killed back to the ground, while others will just have been damaged partway down the branches.

In the "killed to the ground" scenario, all the dead wood above ground should be removed. Less damaged plants need to have the dead wood pruned away after the extent of the damage is more clear. Since leaves are just now emerging on the plants, waiting another week or two before pruning away large portions of a plant would be prudent.

Green Industry Update - Tuesday, Jan. 28

A Green Industry Update, offered through UGA/Cobb County Cooperative Extension, is scheduled for Tuesday, January 28, 2014. Recertification credits are offered in the following categories:

21, 23, 24, 27, 41 - 3 hours
Private - 2 hours
ISA - 2 hours

8:30-9:00           Registration

9:00-9:50           1) Proper Pruning of Trees and Shrubs for Plant Health and Pest Reduction

                          Rick Smith – Owner of The Pruning Guru

9:50-10:00         Break with Q and A

10:00-10:50       2) Proper Pruning of Trees and Shrubs for Plant Health and Pest Reduction

                          Rick Smith – Owner of The Pruning Guru

10:50-11:00       Break with Q and A

11:00-11:50       Mosquito Biology and Control in North Georgia

  Elmer Gray – Medical and Veterinary Entomologist UGA Dept of Entomology

11:50-12:00       Evaluation and Recertification Forms

Moderator will be Neil Tarver, UGA/Cobb County ANR Agent.

To preregister: email emily.harper@cobbcounty.org, or call 770-528-4070.
Cost: $10 per person at the door
Location: Cobb County Water Lab, 662 South Cobb Drive, Marietta, GA 30060

Winterizing Trees

Kim Coder, professor of Tree Biology and Health Care with UGA's Warnell School of Forestry and Natural Resources, has published a list of steps homeowners can take to help insure that their trees make it safely through the winter dormant season.

The list has been posted on the Landscape Alert blog of UGA's Cooperative Extension. This is Coder's “Top 10 List” of things you can do to winterize your trees:

1. Remove or correct structural faults and deadwood that are clearly visible. Try to make small pruning cuts that minimize the exposure of the central heartwood core on branches.
2. Properly prune branches that will touch the ground when loaded with rain and snow. Foliage and branches that are in contact with soil can invite undesirable pests and problems.
3. Remove damaged and declining twigs, branches, and bark. Do not leave pests food and shelter for the winter.
4. Remove any new sprouts that have grown at the tree base, or along stems and branches. Pruning should conserve as many living branches as possible with only a few selective cuts.
5. Spread a thin layer of composted organic mulch to blanket the soil. Cover an area at least as large as the branch spread. Mulch is nature’s of recycling valuable materials, but be careful of pests hitching a ride.
6. Properly wrap new trees that have not developed a corky bark and could be easily damaged. Mechanical injury from the environment, including chewing and rubbing by animals, must be prevented.
7. Aerate soils if they are compacted and poorly drained. It is critical not to damage tree roots in the soil. Saturated and dense soil can suffocate roots.
8. Fertilize with all the essential elements, if they are in short supply within the soil. Be sure to go lightly with nitrogen, especially under large, mature trees and around newly planted trees.
9. Watering may be needed where soils are cool but not frozen, and there has been little precipitation. Winter droughts need treatment with water the same as summer droughts, except it is much easier to over-water in winter.

Pruning, Planting, Fertilizing

Such a busy time of year for the great outdoors here in Cobb County! Vegetable gardeners will have begun planting their summer crops within the last week or so; seedlings are coming up; early-flowering shrubs like azaleas will need to have any pruning done very soon; and the warm-season lawns (Bermudagrass, Centipede, Zoysia, St. Augustine) should have any needed fertilizers applied within the next several weeks.

Zucchini seedlings emerging.                               PHOTO/Amy Whitney

Vegetable gardeners who would like to verify that planting time is now for most of the summer crops can check UGA's Vegetable Planting Chart. The planting dates on the chart are for middle-Georgia, so the dates should be adjusted by a week or two for Cobb County.

With regard to pruning the azaleas, UGA's Frank Watson reports in the 25 April issue of FACES that azaleas should be pruned "now, after they have bloomed, to allow the plants to prepare for blooming next year."

Watson's article explains the two pruning techniques typically applied to azaleas - thinning cuts and heading cuts:

"Thinning refers to the complete removal of branches back to another branch or main trunk. Thinning is used to remove leggy branches that extend beyond the canopy of the plant, to reduce the size of the plant or to remove any damaged or diseased wood. Thinning can be done any time of the year without significant impact on flowering, growth or cold hardiness

"Heading refers to the cutting back of a branch, not necessarily to a side branch. Vigorous new shoots will emerge within 6 inches of the pruning cut. Heading is usually done with three goals in mind: to reduce the size of the plant, to increase the number of branches or to rejuvenate old, overgrown plants. Severe pruning of old, overgrown plants to within 6 to 12 inches of ground level is a common type of heading."

For more information, refer to Watson's article "Azalea Bloom Show is Over so It's Time to Prune and read UGA's "Selecting and Growing Azaleas."

Putting the Pruning Shears to Work

As winter begins to wane, the urge to get busy in the yard, preparing for the spring, is almost overwhelming for many gardeners. If the lawn is planted in a "warm season" turf-type like Bermudagrass, it's too early to do much work on the lawn. It's also too early for planting much of the vegetable garden. However, the flowering trees and shrubs can be a good place to focus some of that gardening energy.

According to the UGA publication "Pruning Ornamental Plants in the Landscape" by  Extension Horticulturists Gary Wade and James Midcap,

"As a general rule, plants that flower before May should be pruned after they bloom, while those that flower after May are considered summer-flowering and can be pruned just prior to spring growth."

The phrase "just prior to spring growth" means that the window of opportunity is going to be closing soon, for many of the summer-flowering shrubs.Wade and Midcap include not only instructions for how to prune woody ornamental plants, but also a useful list of shrubs and small trees to prune in late winter:

Beautyberry	Goldenrain Tree
Camellia	Japanese Barberry
Chaste Tree (Vitex)	Japanese Spirea
Cranberrybush Viburnum	Mimosa
Crape myrtle	Nandina
Floribunda roses	Rose-of-Sharon (Althea)
Frangrant Tea Olive	Sourwood
Grandiflora roses	Anthony Waterer Spirea
Glossy Abelia	Sweetshrub

For roses, an illustration within the publication (and pasted here) offers gardeners some additional guidance in how to shape the different types of roses. More information about rose culture in Georgia can be found in the UGA publication "Roses in Georgia, Selecting and Growing Techniques."

Additional information about pruning crape myrtle, an especially well-loved landscape shrub, can be found in the UGA publication "Crape Myrtle Culture."

Hopefully, the publications linked above will provide some direction for the gardener's pent-up energies as he or she contemplates the coming of another beautiful spring.