So, What Plant Problem Do You Want?

August 15th, 2017

   Not counting plastic ones, no plant is immune from trouble.

Lily of the valley very often ends up looking like this by mid-summer.

   Bad stuff can happen to any plant —  yes, even natives and ones on the low-care, “trouble-free” lists.

   Once you accept that, what makes the most sense is leaning toward ones with the best track records, in real-life gardens, in our area.

   Fortunately, that’s predictable. Watch plants well enough here for long enough, and it’s clear that some of them are way more likely to run into trouble than others.

   Read George’s Bottom 10 Annual Flowers, George’s Bottom 10 Perennial Flowers, George’s Bottom 10 Shrubs, George’s Bottom 10 Trees, and George’s 10 Landscape Plants You’ll Probably Kill.

   Then Read George’s Top 10 Annual Flowers, George’s Top 10 Perennial Flowers, George’s Top 10 Flowering Shrubs, George’s Top 10 Small Trees, and George’s Top 10 Shade Trees.

   The problem is that gardeners often don’t know which is which. Not everyone concludes the same thing either. New information and missing or misinformation gums up the plant selection further.

  A case in point is one of the newest threats to a common landscape plant – boxwood blight.

   This fungal disease came to the United States around 2011 and has been detected on a small number of boxwoods in nine Pennsylvania counties.

   The state Department of Agriculture began a disease-control, quarantine program in 2016, and experts have been advising “caution” about planting boxwoods. Some garden centers even stopped carrying them – or started steering gardeners toward alternatives.

   The reality, though, is that this isn’t nearly as virile and fast-spreading of a disease as, for example, the downy mildew disease that wiped out almost everyone’s impatiens five summers ago.

   It also isn’t shaping up as sure-fire species doom like the emerald ash borer that’s killing most every ash tree in its wake.

   So far, boxwood blight hasn’t translated into much trouble in Pennsylvania.

   Sara May at Penn State’s Disease Clinic tells me she’s seen just three cases of boxwood blight submitted statewide in the last two years.

Boxwood blight is a fatal disease, but so far it’s not causing big trouble in Pennsylvania.
Credit: Va. Tech Extension

   Dana Rhodes, a regulator in the state Department of Agriculture’s Bureau of Plant Industry, says the disease is lurking but has actually decreased in incidence in the past year.

“Since the boxwood blight quarantine was put into action in June 2016, Pennsylvania has seen a reduction in the number of positive boxwood for the disease,” she says.

   And, she adds, “No Pennsylvania boxwood producer has been found to have boxwood blight.”

   The good news here is that the fungus that causes boxwood blight apparently isn’t as rampant of a spreader as many bugs and diseases.

   The most likely way to get blight is by bringing in already-infected plants or by moving tools or other materials that are carrying spores from infected plants. (Pachysandra and sweetbox are other plants that can get this blight, by the way.)

   This characteristic gives growers and regulators a fighting chance of keeping a lid on this disease. Plants are being closely monitored at both the grower level and retail level, and so far, the state has come up clean.

   I mention all of this because the blight attention has skewed gardeners away from what I believe is still a solid choice and toward alternatives that have a better chance of failing from “old” and accepted problems.

   Some plants-people, for example, are advising gardeners to skip boxwoods and go with the similar-habit Japanese hollies if they want a compact, rounded, broadleaf evergreen.

   Others are touting the native inkberry holly.

   In my travels into thousands of local gardens over the past 25 years, I’ve seen a lot of trouble with both of those.

   Japanese hollies don’t transplant well, and so a high percentage of them die in the first year or two – especially if they’re sited poorly, planted in compacted soil, and/or not watered. Some plants are forgiving of that, but some – like this one – aren’t.

Here’s a planting of inkberry holly not looking so good in a Hampden Twp. office-building parking lot.

   Japanese hollies also often run into root-rot disease, which stunts or kills them.

   Inkberry hollies are picky about site as well. Look at the many dying ones along sunny driveways and in commercial parking-lot islands to measure their forgivability. The photo at right is just one example of the many suffering inkberry plantings I’ve seen.

   Even in ideal settings, inkberries tend to develop “bare legs” over time, and they’re notorious for growing at uneven rates, which is a detriment if you’re planting in masses or a formal line.

   Boxwoods have their downfalls, too, like psyllids, mites and leaf miners (bugs), winter wind, and a somewhat mysterious condition known as “boxwood decline.”

   But given what I’ve seen – and still see – you’ll likely have a better chance of success with boxwoods than either Japanese or inkberry hollies.

   I have no qualms about buying boxwoods. Until blight starts showing up in real life, I’m reluctant to write off this useful species.

   Knowing that growers and regulators are paying close attention makes me even more confident.

   I was talking to Reuben Fisher at Lurgan Greenhouses about blight a few weeks ago, and he said the state Ag Department inspector was just in there the week before checking his boxwoods.

   “If there was anything on them, they would have pulled them all right then and there,” Reuben said. “That’s fine with me. We welcome the inspectors to help make sure there aren’t problems.”

   If you’re still concerned, some cultivars have been found to be at least somewhat resistant to the new blight, including ‘Dee Runk,’ ‘Green Beauty,’ ‘Winter Gem,’ ‘Green Gem,’ and ‘Franklin’s Gem’ as well as the species Buxus harlandii.

   One other bit of input that carries a lot of weight with me. Longwood Gardens just reopened its Main Fountain Garden this May, a $90 million project that included replanting the entire 5-acre garden. Staff there went with hundreds of new boxwoods — primarily the ‘Green Beauty’ variety that I’d also recommend. If boxwood blight is such a threat and if Japanese hollies and inkberry hollies are such better options, why would Longwood make such a big investment in new boxwoods?

   The University of Virginia has an excellent bulletin all about boxwood blight if you want to read more.

   The lesson in this is that we shouldn’t overreact to every new threat. We should look at each one case by case and decide based on the best evidence at hand.

   The bigger lesson is that a whole lot of common plants bought every day come with near-certain problems. We shouldn’t under-react to those just as we shouldn’t over-react to a new problem.

   For now, I’ll take my chances any day with a boxwood over a mountain laurel, Japanese holly or inkberry.