That’s right, I don’t like boxwood; do you want to know why I don’t like boxwood?
Before I get on my soap box about boxwoods did you know there are around 90 species of boxwood worldwide, but only a few are temperate plants. The rest are topicals. There are over 180 taxa (species, varieties, and cultivars) being grown in the national boxwood collection at the National Arboretum.
Looking on the bright side there are very few plants that radiate elegance like the boxwood, but somehow that elegance is being overshadowed by a plethora of problems. Thus the reason why I don’t like boxwoods.
Boxwoods are the number one plant with problems that I receive phone calls about, almost every day. Just this past week I have had three samples brought to my office plus four phone calls cornering my dying boxwoods.
The problem your boxwoods are experiencing is more than likely caused by the grower, yes that’s you. Wow, what, wait, how can you say that Mr. County Agent Man? I can say that because when I make a visit to examine a suffering and dying boxwood I see the same problems over and over that have been caused from the lack of proper care.
Problems such as wet soil, improper pruning, improper mulching, not to mention all the dead leaves and excess mulch piled up on the trunk sometimes a foot or thicker. I find the insect boxwood leafminer having a jolly good time ravaging the leaves of the boxwood along with other insects such as scale sucking every bit of nutrition out of the plant. Oh, did I mention mites and mealy bugs. What about the 2016 and 2007 drought that killed a lot of plants, think your boxwoods suffered? Trees and shrubs are still suffering today from those droughts.
When I ask questions about fertilization I get the “yes I have fertilized my boxwood” which leads me asking more questions. One such question is “have you had a soil test done to determine soil pH and what nutrients your boxwood might be needing?”
But Boxwood Hater Guy, my boxwoods are 100 years old and have been fine until now! In all actuality they have not been fine, they have been declining for years, you just did not recognize that your boxwoods were declining.
Almost every time when I start asking questions folks get defensive. Is this because you feel like you’re being accused of boxwood abuse? I bet you’re guilty!
Next question comes from you, “What can I spray or pour on it to make it all better?” Sorry, I don’t have some magical whiffle dust to fix a problem that has been festering for years. This problem(s) does not come with a simple fix. Many will not believe me and scoff at my recommendations, oh well even more reasons to hate the boxwood.
Boxwood do’s, don’ts, likes, and all stuff boxwood
Boxwood roots grow shallow, within the top 15 inches of soil, and the roots extend out several times the canopy spread. A mature boxwood is difficult to transplant due to the extensive root mass and percent of root loss during transplant.
Boxwood prefers an alkaline pH, in the range of 6.8 to 7.5 for optimum growth. It often suffers nutritional deficiencies at low pH. Dolomite lime is recommended to increase pH because it contains magnesium which boxwood likes. Do not plant boxwood adjacent to azaleas, camellias, gardenias or other acid-loving plants.
Boxwood respond better to late fall and early spring fertilization because it promotes root growth. Roots grow all winter and spring/early summer when soil temperatures are not so hot. Fall fertilization help minimizes winter leaf bronzing which is often linked to nutritional deficiencies. Tip bronzing for instance indicates magnesium deficiency.
Hand thinning is much better than shearing. Shearing results in a thick, dense outer canopy, poor air flow within the foliage, and encourages leaf and twig diseases. Branch die-back can often be attributed to shearing and poor cultural conditions.
Use hand pruners to make selective thinning cuts inside the canopy on selected branches. Thinning gradually controls plant size, but more importantly it opens the canopy and improves air flow and light penetration which are important for maintaining leaves.
Boxwood does not respond well to severe pruning. Exposing the old wood often results in frost/winter injury and sunscald on the trunk and branches.
Boxwood leaves remain on plants for 3 years before they shed. It’s important to keep them on the plant as long as possible by preventing inner leaves from becoming shaded. It’s also important to maintain leaves as far down within the canopy as possible.
Boxwood problems are caused by numerous insects and diseases, including leaf miner, mites and scales, but most of these are encouraged by poor cultural/management conditions or improper soil pH. English boxwood does not get leaf miners because the leaves contain an alkaloid that kills the insect.
Some key pest of the boxwood:
Insects: leafminer, psyllid, mealy bugs, mites, scale.
Diseases: Phytophthora root rot, Volutella stem blight, and Boxwood Blight
Boxwood Decline: caused by many stress(es) that weaken the plant over time. Stresses from lack of nutrition, wrong soil pH, incorrect pruning, insects, diseases, etc.
“And now you know the rest of the story!” Where have I heard that before, sure does sound familiar?