Problems with oranges may mean the rootstock is growing | Home/Garden

Garden columnist Dan Gill answers readers’ questions each week. To send a question, email Gill at gnogardening@agcenter.lsu.edu.

Is there any advantage or danger if I prune my hibiscus bushes from their current 6 to 7 feet down to 3 to 4 feet before the chance of hard freezes? If I prune them back to 3 to 4 feet, they will be easier to cover and protect during freezes. On the other hand, I don’t want them sprouting new growth right in the worst of winter. What is your thinking on this? Keith Lang

What you are proposing to do is reasonable and even necessary for tropical plants too large to practically cover when we experience severe freezes this winter. But, as to timing, I would wait and do this just before a major freeze. If you cut them back now and the weather stays mild, they will likely start to send out new growth. And you are right to be concerned about that happening. The new growth would be very sensitive to cold damage.

When it comes to light to moderate freezes in the upper 20s or higher, the larger the plant the more resistant to the cold it is. So, during this time of moderate weather and light freezes, leaving the plants larger is better. They don’t need to be covered. If some cold damage happens to the upper parts of the plant during light freezes, that is not a big issue.

So, wait for an imminent severe freeze to cut them back. When temperatures in the mid-20s or lower are predicted, cut back the hibiscuses to facilitate covering and protecting them. If temperatures will go down to 20 degrees or lower, add a heat source under the covers such as small, outdoor, incandescent Christmas lights.

I am trying to cover a fence with green foliage using yellow jessamine vines. The vines I planted last spring have grown very well and are nice and full at the top. When they reached the top of the fence, I cut them back hoping to increase the foliage at the bottom and middle of the fence. But those areas continue to be very sparse. Please let me know how I can achieve fuller vines at the base and middle. Jamie Simms

The problem is that you allowed the vines to run quickly up to the top without forcing them to fill in lower portions of the fence first. Cutting back the tops will not cause the lower parts to fill out. Plants sprout out where the pruning cuts are made — not from lower down. In other words, when you trim back the top you stimulate new growth at the top, not in the lower parts of the vine.

Many gardeners do not realize how important it is to direct how the vine grows from the time it is planted and through its life in the garden.

Vines generally want to grow straight up and get as tall as possible as fast as possible. When training a vine on a fence, trellis or lattice panel, it is generally desirable for the vine to be lush and full from the ground up.

Many gardeners training a vine are dismayed to find that the vine is all up at the top of the support, and there is nothing but bare stems on the lower part of the plant. Once that has occurred, it’s hard to correct the situation. It’s best to prevent it by training the vine properly from an early stage.

As soon as a vine is planted, begin weaving the existing vine stems horizontally along the bottom portion of the fence. As the vine begins to grow upward, unwrap the vine and continue to force it to grow sideways. Weave it horizontally through the fence while gradually allowing the vine to grow up the support. As you continue to do this over time, you will create a vine that is full and attractive on the lower part of the support as well as the upper portion.

Once the vine reaches the top of the fence, don’t simply cut it back. Instead, take the long stems waving in the air, bend them around and weave them back down the lattice panel. That will help fill in the top of the lattice panel without creating the thick, bushy top that pruning back would create.

It’s too late to train the existing vines like this. But, at this point you could plant additional vines along the fence and train them to fill in the lower portions of the fence using this advice.

Garden tips

ORNAMENTAL GRASSES: Most of them, other than pampas grass and pink muhly grass, go dormant for the winter and turn brown. Feel free to cut them back hard when the foliage is brown and no longer attractive. On the other hand, with their flower plumes and graceful foliage, many gardeners like the way ornamental grasses look when dormant; so, leave them if you like. Make sure to cut them back by early March at the latest, however, to make way for new growth.

FRUIT TREES: December and January are ideal months for planting hardy fruit trees, bushes and vines such as apples, pears, plums, peaches, nectarines, grapes, blueberries, blackberries, persimmons and others. I recommend planting citrus trees in late February or early March after the coldest part of the winter is past, since hard freezes could severely damage or kill the young trees. Tropical fruit, such as avocados, bananas and papayas, should not be planted out until April.

HERBS FOR NOW: Hardy herbs that can be planted now include thyme, sage, rosemary, oregano, French tarragon, lavender, chives, cilantro, dill, mints and parsley.

CAMELLIA CARE: Open flowers of camellias can be damaged by hard freezes in the mid- to upper 20s, but the buds are generally not damaged. They will bloom out normally later on. Camellia bushes appreciate a mulch two or three inches thick over their roots to help keep the soil evenly moist. Extended spells of dry weather can stress camellia and cause buds not to open.