What’s Happening Here?
I thought I’d open the newsletter with a problem I’m guessing many perennial growers have faced on at least one occasion, but most likely have observed this issue numerous times over the years.
You can easily see the obvious abnormal appearance of the penstemon and its leaves. I’d say this is a more severe case, as the symptoms often appear more subtle than what I’m showing here.
Did someone apply a chemical application incorrectly? Are the fertility levels out of whack? Was the plant exposed to a severe insect infestation? These are all valid questions, but does any of them led to the correct answer? Perhaps—you’ll have to wait to find out.
Fortunately, I’m not going to make you wait until the next newsletter. Simply stick around and I’ll reveal the answer very soon.
New from Terra Nova
Sedum Mocha Magic
Mocha Magic offers good color throughout the seasons. The young foliage starts off blue, turns gray blue and then transitions to a chocolate brown as it matures. It develops large clusters of light mocha foam-colored flowers, offering great contrast with the dark stems and foliage. The plants are sturdy, growing up to 26- to 32-in. tall and they don't fall open like other upright sedums often do. Hardy to Zone 4.
Cuttings are available through Danziger and rooted liners are available from ThinkPlants.
Agastache Prince’s Plume
Prince’s Plume exudes royalty with its stately, elegant, lavender-violet flowers. Plants with fragrant foliage cover themselves with fragrant flower spikes beginning in early summer and continuing until frost. It grows up to 36-in. tall and is a pollinator magnet, as Prince’s Plume attracts tons of bees, bumblebees, hummingbirds and other pollinators into the landscape. Hardy to Zone 5.
Upcoming Events
As the year winds down, there are several trade events to consider attending. Here are several I thought might be worth considering. Click on the name of each event to learn more.
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November 5-6, 2025 |
DeLand, Florida
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November 5-7, 2025 |
Shawnee, Oklahoma
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November 12-13, 2025 |
Manchester, New Hampshire
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November 13, 2025 |
Storrs, Connecticut
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November 13-14, 2025 |
Red Deer, Alberta Canada
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December 8-11, 2025 |
New Orleans, Louisiana
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December 9-11, 2025 |
Grand Rapids, Michigan
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The Answer is …
I showed this image of a penstemon at the top of the newsletter and asked if you knew what was causing this abnormal appearance. The only real clues I provided were that if you’ve grown perennials, you’ve likely experienced this problem and that it often appears less severe than what I’m showing you. Here’s one more clue for you: dozens of different perennials are susceptible to this problem.
When diagnosing plant issues, I encourage scouts and growers to take closer looks in addition to observing the bigger picture. As you can see in the image above, there isn't much that looks normal on these leaves.
Have you narrowed it down to your final answer? If you answered the penstemon has a virus, you earned yourself a virtual gold star. If your answer was more specific and you said INSV (Impatiens Necrotic Spot Virus), I’ll give you a bonus star. Congrats!
This Problem is Problematic
The unfortunate thing with viruses is there are no cures for them. Once a plant has a virus, there's nothing growers can do to remove the virus from the plant. This makes for a lot of unhappy growers (and perhaps a few happy refuse companies).
Impatiens Necrotic Spot Virus (INSV) is one of the more common viruses perennials are susceptible to. INSV is a tospovirus that's primarily transmitted to or vectored to crops by western flower thrips or with vegetative propagation.
Symptoms of INSV can appear as black, brown, reddish or yellowish concentric rings, spots or necrotic streaks on the leaves. It can also cause distorted growth, stunting and/or bud drop. These symptoms can vary with the type of plant infected, plant age, how long it’s been infected, the environment and the amount of stress it’s experienced.
ImmunStrip for onsite INSV testing.
It can be difficult to rely solely on visual symptoms to properly diagnosis INSV or other plant viruses. For this reason, I recommend growers send symptomatic plant tissues to virus testing labs such as
Agdia or plant diagnostic clinics at many reputable universities. Agdia has developed practical and cost-effective
ImmunoStrip test kits for identifying INSV and other viruses quickly and reliably onsite.
Since there's currently no cure for plants infected with viruses, it’s best to remove any symptomatic plants from the production facility and discard them once they've been found, tested and confirmed to have INSV (or any other virus). Failure to remove symptomatic plants from the crop area could result in significantly more infected plants down the road.
Follow These 10 Steps
grayscaleppc.com
Since there are no curable treatments for viruses, it’s important for growers to take steps to reduce the likelihood viruses will infect their crops.
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It’s important to start with clean, virus-free starting materials. When possible, obtain starting materials from companies who have virus indexing programs in place or when performing your own propagation, and obtain cuttings from stock plant producers who take numerous precautions and test their stock plants diligently to ensure healthy, virus-indexed cuttings reach their customers. Keep in mind this ensures a clean start, but viruses often occur after crops are placed into production.
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Properly clean the production facilities using good cleaners and disinfectants (I can help you with this).
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Remove all weeds from in and around the production areas to limit potential sources of viruses (weeds are a common carrier of plant viruses).
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Do not allow employees to smoke in production areas.
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Disinfect used containers and trays or use new ones for each crop.
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Take steps to reduce the mechanical transmission of viruses such as properly disinfecting scissors, shears and other tools used to maintain crops.
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Require employees to wash their hands or change gloves between each crop they're working on.
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Never propagate plants that are infected with viruses.
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Scout for insect vectors and watch for early detection of plants expressing virus symptoms. Implement preventive programs for managing insect vectors on susceptible crops.
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Immediately remove plants with virus symptoms to prevent the infection from spreading to other plants.
With no known control methods, prevention is the only approach growers can take to reduce the occurrence of plant viruses. The 10 steps above will go a long way towards preventing viruses from becoming problematic.
My email is ppilon@ballpublishing.com if you have any comments, article suggestions or if you'd just like to say hello.
Best regards,
Paul Pilon
Editor-at-Large—Perennial Pulse
National Sales Manager—Pace 49, Inc.
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