Late Winter Pruning Primer

By: Sherie Caffey, CSU Extension-Pueblo County Horticulture Agent

With the holidays behind us, spring is right around the corner. It might seem too soon to start thinking about the outdoors, but it is actually the perfect time to start thinking about pruning your trees and shrubs. Timing is key when it comes to pruning. You also need to consider what you are pruning and what your goals are. 

Late winter is a great time to prune

Any dead, diseased, or damaged tissue on a tree can be removed any time of year. If you are doing very light pruning (less than 10% of the foliage) of live wood, that can also be done at any time of the year. Late winter is considered the routine time for pruning mature trees, before the buds start to swell. Some trees like Elms, Hackberry, Maples, and Mulberries may “bleed” when pruned in late winter. This a cosmetic concern, but if you prefer to wait to prune these species, you can prune them midsummer, after the spring growth flush.

Maples and other trees may "bleed" when pruned in winter

Young shade trees require very little pruning if any, but the training a tree receives when it is young will determine its structure for life. Late winter is the perfect time to do some structural training of a young tree. CSU Extension has a multi-page document that describes in detail how to properly train a young tree, it can be found here: http://www.ext.colostate.edu/mg/Gardennotes/613.pdf.

Spring flowering shrubs such as forsythia, viburnum, lilac, and honeysuckle bloom on the twigs that grew the previous summer. The flower buds develop starting in midsummer and go through the fall to make buds for the following spring. If you were to prune these shrubs in the in the fall or now, you would be removing the wood with next year’s buds, which would prevent flowering. To thin these shrubs, prune right after they bloom. It is also recommended to deadhead spent flowers so the plant can focus energy on foliage and new buds rather than making seed pods.

Prune lilacs after they bloom

Summer flowering shrubs like butterfly bush, blue mist spirea, and rose of Sharon bloom on wood that grew earlier in the same growing season. These types of shrubs set buds in mid to late spring, and then bloom in the summer. You can prune summer flowering shrubs now into early spring before growth begins. Removing older wood will allow better sunlight penetration, and will encourage flowering throughout the shrub, rather than just on the top where there is a lot of sunlight.

            Pruning large, mature shade trees is often a task that can become unsafe for most home gardeners. Hiring a professional to handle these large pruning jobs is the safest approach. Look for an arborist that is certified by the International Society of Arboriculture (ISA). You can find a list of ISA certified arborists here: http://www.treesaregood.org/findanarborist. 

The Lesser of Two Weevils

Posted by Jessica Wong, CSU Department of Bioagricultural Sciences and Pest Management

I like weevils. Weevils are funny little beetles with silly looking “snouts” and they have a name begging to be made into puns. It’s too bad that some of them are also annoying pests that chew on the roots and leaves of a variety of garden plants. Perhaps some might even call them weevil (sorry, but you knew it was coming).

Weevil. Photo by Stephen Luk, bugguide.net

In Colorado some of the more common root weevils include strawberry root weevil (Otiorhynchus ovatus), rough strawberry root weevil (Otiorhynchus rugostriatus), black vine weevil (Otiorhynchus sulcatus) and lilac root weevil (Otiorhynchus meridionalis). Lilac, privet, peony, euonymus, heuchera, hosta, rose, strawberry, raspberry, white clover, dandelion, dahlia, and mint are few examples of plants that can be fed upon by one or more of these root weevil species.

Lilac root weevil on peony. Photo by Whitney Cranshaw

Root weevil larvae are legless, cream-colored grubs with orange-brown heads that can be found in the soil in winter. Starting around late-winter through early-spring the grubs pupate in the soil before emerging as adults mid- to late-spring. The adults cannot fly, so they will likely feed on the same plant it developed on as a larva. 

Black vine weevil larva. Photo by Peggy Greb, bugwood.org

Grubs feed on roots, which may cause decline or dieback in plants if the feeding is extensive, but this is quite uncommon in landscape plantings. Adults feed on leaves at night and cause leaf notching. It’s likely that a gardener will not notice the damage until the daytime, but just because one sees no weevil does not mean weevil is not there…. Fortunately, adult root weevil damage is typically only aesthetic and the plant will tolerate a bit of herbivory. If you think you need to manage the pest, check out Dr. Whitney Cranshaw’s Root Weevil Fact Sheet for control methods. 

Circular shaped cuts from leafcutter bee. Photo by Whitney Cranshaw

Adult root weevil U-shaped feeding damage. Photo by Whitney Cranshaw

Sometimes adult root weevil damage is mistaken for leafcutter bee damage, or vice versa. Leaf notching caused by root weevils tends to be jagged and U-shaped, while leafcutter bee damage is smooth and shaped like a half-moon. If you’re still having a hard time identifying the insect or the damage contact your local Extension office. Weevil help you!