What’s happening now is the question of the day.
Lily-of-the-valley tree (sourwood, Oxydendrum arboretum) is blooming in all its panicled glory.
Hydrangeas continue to astound. Japanese beetle legions are — legions — on many plants.
Dog-vomit fungus adorns mulch and will continue to do so.
Salmon-colored joe-pye weed and electric-purple ironweed adorn meadow areas with their harbinger of late-summer and early fall flower heads.
Swamp rose-mallow (Hibiscus moscheutos) blooms in all its dinner plate-sized sensations.
The shapes of mature silver lindens and red oaks, oh my. So, let us look in a little more detail at our mid-summer and beyond environment.
Planetree Perseverance. As predicted on June 11, planetrees, especially the more susceptible American planetree (sycamore, Platanus occidentalis) that looked almost leafless due to sycamore anthracnose in May and June throughout much of Ohio, have now largely re-foliated and look fine. Cool, moist conditions during leaf emergence, so key to disease development, are past history and trees recovered nicely.
All Hail Honeylocust. Orange-yellow discoloration on stems, elliptical cracking on those stems. Are these fungal cankers on this backyard thornless honeylocust (Gleditsia triacanthos var. inermis ‘Imperial’) I saw in Denver? Not totally sure, but I suspect the smoking gun is the homeowner’s report of the environmental history of major hailstorms this spring and summer — and the “What Exactly Do You See” question #6 of Plant Problem Diagnostics. What I exactly saw was the damage in question only occurring on — upper stem surfaces.
Aesculus Avoidance. On a Denver street, a reminder of home — Ohio buckeye! Leaf scorch in the hot summer heat, and some insect feeding, but — whither the Guignardia leaf blotch fungal diseases, common on the genus Aesculus (buckeyes and horsechestnuts)? Not there because Denver has such low humidity and rainfall during leaf emergence in spring.
Waterlilies. Or is it water-lilies? It certainly is not water lilies. What am I going on about? Well, the rule of thumb is that when a plant, or an insect is not a “true” representative of its name, then it should be written as a compound name. Think pineapple. Neither a pine nor an apple, it would be misleading to call it a pine apple, making the reader think of a pine type of apple. This protocol is not always used, but can be useful.
So, waterlilies. Embarrassed am I that until a recent discussion I just assumed that waterlilies were a type of lily or at least closely related. Not so. True lilies are in the genus Lilium and at least you would suspect that they are in the Lily family, the Liliaceae. Talking with some of my plant buds about waterlilies, we discussed their family as the Nymphaceae, and soon got into their additional taxonomy.
Not only are waterlilies not lilies or in the lily family they are really divergent. Waterlilies or water-lilies are dicots (two seed leaves, cotyledons). Lilies are monocots (one seed leaf). This is a big difference. For example, monocots and dicots have different types of vascular systems, the phloem that transports food to the stems and roots from the leaves and the xylem that transports water and minerals from the soil and roots to the stem and leaves.
This has much relevance, including whether lilies and waterlilies are affected by specific herbicides. For example, the same herbicide that controls dandelions (a dicot) will not damage turfgrass (a monocot) at a given rate.
Phytophthora ramorum. As you may have read or heard, this water mold organism that causes ramorum blight on more than 100 host plants, including rhododendron and lilac, and sudden oak death (SOD) in coastal areas of California and Oregon, was intercepted by the Ohio Department of Agriculture in their plant regulatory program. It was found at Walmart and Rural King locations in Ohio and other Eastern states. Let us put this find into perspective.
SOD has proven to be deadly in California and the Pacific Northwest on oaks (Quercus) and tanoaks (Notholithocarpus). On other hosts, this pathogen causes leaf spots and branch dieback. This sounds ominous, but let’s put it into perspective. Though this pathogen was found on rhododendrons and lilacs intercepted here, there was no shipment of oaks with SOD.
For context, let us again remember the Plant Disease Triangle: a susceptible host, a virulent pathogen, and an environment conducive to disease are all necessary for a particular disease to occur. Over the almost 25 years in which SOD and ramorum blight have been regulated disease issues, we do not know of any cases of this disease becoming established in the U.S. other than those coastal areas of California and the Pacific Northwest.
Although it is impossible to completely know for certain the potential risk of this pathogen becoming established here, Ohio is not considered to be a particularly likely candidate for establishment of SOD. P. ramorum has never been detected before in Ohio production nurseries, landscapes, or forests. That said, the vigilance of Ohio Department of Agriculture and our plant regulatory system should be lauded relative to this interception.
Let us proceed with caution. If bought rhododendrons or lilacs at Walmart or Rural King between March and May of this year and you suspect they may be infected, drawing from the ODA news release, "Plants can be destroyed by burning, deep burial or double-bagging the plant, including the root ball, in heavy duty trash bags for disposal into a sanitary landfill (where allowable). Consumers should not compost or dispose of the plant material in municipal yard waste."
In addition, it is important to keep in mind there are many different diseases, insects, and physiological problems that may occur on rhododendrons, lilacs, and oak. To sharpen your plant problem diagnostic skills, we will make a point of reviewing some of these at diagnostic training events yet to come this summer and fall. This includes the Ohio Plant Diagnostic Workshop on the OSU-Wooster Campus on Sept. 6.
You can access the ODA news release by visiting https://agri.ohio.gov/wps/portal/gov/oda/divisions/plant-health/invasive-pests/p-ramorum-survey
And as the summer progresses, let us enjoy life to its fullest, a la Emily Dickinson. “Here is a little forest/Whose leaf is ever green; Here is a brighter garden/ Where not a frost has been; In its unfading flowers I hear the bright bee hum; Prithee, my brother, Into my garden come!”
Finally, as Albert Einstein said in a building-sized mural I saw in Denver recently: Question Everything!
Jim Chatfield is a horticultural educator with Ohio State University Extension. If you have questions about caring for your garden, write to email@example.com or call 330-466-0270. Please include your phone number if you write.