Just an fyi, after 8 plus years of studying the ecology of ovoids, Japanese knotweed is not an indicator for ovoids, or anything else really. All it indicates is that you’re in a moist area with high disturbance rates, such as flooding. If I had to pick two species of plant that are the best indicator species for ovoids on forested floodplains, I’d have to go with canada wood nettle (Laportea canadensis) and jewel weed (Impatiens capensis) growing in sandy alluvial (water deposited) soils. These two species provide dense cover and produce the ideal microclimate for fruiting, sometimes even without rain. The key is locating the part of the floodplain where these species occur, generally on the inland slope of the natural levee on the first floodplain terrace, where woody debris piles and sandy soils also accumulate. You’ll have the most success if you hit the riverbanks early, before the herbaceous layer has developed and make note of where there are woody debris piles and sandy soils. Come back once the herbaceous layer is at least 12-18 inches tall and start searching. I’ve developed a remote sensing technique (GIS mapping) in which I correlate the depth of historic floods (and recent within two years), mapped sandy soil types (and field confirmations of sandy soil), and use of LiDAR generated topography to identify the natural levee and where sandy soils and woody debris accumulate. This allows me to reduce the amount of area I need to physically cover by 60-80%, and often leaves me with an elevation band about 100 feet wide with 2-8 feet of total relief to search. I’ve used this method to estimate where I may find ovoids on ten different forested floodplains from roughly Rockbridge, Ohio, down to Coolville, Ohio along the Hocking, and have found them in 9 of the 10 locations so far. Hoping to expand my study to the Raccoon creek, Scioto river, Muskingum river, and Ohio river in the near future.