If you think you need to regularly prune your landscape plants, Tony Gonzales wants to suggest a different perspective.
“There really is no reason to prune except for disease, a safety hazard or if the plant is dying,” says Gonzales, a gardener with Tucson Botanical Gardens.
“Really,” he adds, “you want to let the plants just do their thing and be beautiful.”
Many times people prune for reasons that have nothing to do with the plant. It may be growing into a walkway or street or overtaking its space in the yard.
Pruning often is done for our human sensibilities, not for the health of the plants. That’s why some gardeners tend to want to cut off dead or scraggly parts, suggests Robin Lansing, a fellow Tucson Botanical Gardens gardener.
“As an aesthetic, what can you handle looking at?” she asks regarding trees that might have drooping branches or plants that suffer sunburn that isn’t damaging.
Arborist Angelo Romeo says you need to prune with a purpose. “A lot of people are way too concerned and want to prune,” he says. “Ask why you want to prune.”
When it comes to pruning — or trimming and cleaning up — plants, the three plant-maintenance experts had some suggestions.
TREES
Trees can be pruned anytime for a “functional purpose,” says Romeo, owner of Romeo Tree Service and producer of “Mesquites & Palo Verdes, A Home Owner’s Guide Video.”
That includes branches that are affecting safety or access or are diseased, broken or dead.
Cuts that help the tree, such as reducing the canopy or strengthening the structure, should be delayed until the optimum time, he says. You’ll need to know how your particular tree grows.
Mesquite and palo verde, for instance, store nutrients for a blast of new growth in the late winter and early spring.
“The ideal time is to prune just before the tree gets its growth spurt,” says Angelo. If you cut right after that, all of those nutrients were just wasted on new growth that was cut away.
Also, pruning at this time allows you to control where the new growth will occur.
“If you don’t prune before budding or new growth,” he adds, “wait six to eight weeks, after the tree is fully leafed so it can take advantage of that material.”
Pruning these desert trees in the winter cold will cause wounds to heal slowly, opening it to disease and pests, he says.
Another pruning opportunity for mesquite and palo verde is in the summer, when wounds heal quickly. Romeo adds that some arborists believe more of the tree dies back when pruned in extreme heat.
Some arborists also believe that pruning at the end of summer can keep a mesquite or palo verde small, he says. This has not been his experience, however.
For citrus trees, Romeo suggests light pruning. Keep damaged leaves and branches in warm, sunny months to protect interior branches from sunburn and in the winter to protect the living parts from damaging cold.
SHRUBS AND FLOWERS
The idea of using frost- or freeze-damaged foliage to protect wintering plants also applies to many shrubs such as Texas ranger, says Lansing.
“Especially for a big shrub, the top part that has frosted over is now a protection for the layer underneath,” she says.
After the threat of damaging cold is over, go ahead and trim out the dead parts of the ranger, as well as Mexican bird of paradise, bougainvillea, lantana and other woody plants. But it’s not necessary in order for them to grow out.
Many plants that go dormant in the winter, such as Mexican bird of paradise and lantana, tend to look nicer in their growing seasons when the dead parts are cut away, Lansing says.
Rangers shouldn’t be regularly trimmed from the top and especially not into a “sculpture,” says Lansing. Instead, thin out the entire plant to maintain its natural shape. “You want to get the old stuff out of the way so the sun can get in it,” she says.
Reducing some flowering plants forces them to continue blooming. Roses, in particular, need regular pruning twice a year — once each in winter and fall — to encourage flowering.
Deadhead, or remove, spent flowers anytime to do the same thing.
The idea is that taking away the source of seeds will force a plant to continue flowering to produce more seed.
Deadhead “when the flower starts to look poorly,” Lansing says. “You don’t have to wait until it’s super dead.”
Some flowers have seeds in a casing below the petals, not within the flower itself. Be sure to snip those off, too.
SUCCULENTS
Gonzales makes one loud plea: Stop needlessly trimming agaves.
“With the blue agave, a landscaping technique is to cut off the bottom leaves,” he explains. “They turn into pineapple things.”
Agaves, like all plants, need their leaves to make energy to grow, he says. Cutting away healthy leaves slows growth.
Bottom leaves in an agave eventually do die. They’re no longer needed if it’s easy for you to pull them off.
Do not cut off freeze damage from a cactus or succulent until the threat of damaging cold is over, Gonzales says.
The cut won’t quickly scab over in the cold and the plant may become infected. Often, succulents will grow around or over the freeze damage.
“If you’re worried that the damage is too severe and the plant continues rotting, you can cut off the rotting part,” he says. Use a very clean blade to avoid spreading any disease.
If you have to prune a succulent because it’s a safety hazard or overgrowing its space, you can plant that removed piece and get another plant.
