By Bryan Fischer, Curator of Plant Collections at The Gardens on Spring Creek
Thanks to our generally dry climate, we Front Range gardeners have historically contended with relatively few rose pests and pathogens. That’s changed in the last decade with the arrival of the Japanese beetle, which has rapidly become a barrier to growing good-looking roses. Trying to eliminate beetles from your yard is a waste of effort, as these pests are highly mobile and emerge from any untreated, irrigated turf in the area, even including lawns down the block. Because pesticide use is often an unappealing option, many growers now favor rose varieties that bloom early or late and pause mid-season—avoiding peak Japanese beetle activity, which occurs in a massive flush from mid-June through late August. Keep reading to explore Front Range rose selections known to skirt the worst of Japanese beetle feeding.
Among the most vigorous and adaptable for tough or large sites, species roses like Rosa spinosissima (previously Rosa pimpinellifolia) provide a spectacular spring display. R. spinosissima, or burnet rose, is a personal favorite thanks to its effusive covering of gently fragrant, five-petaled, pure white flowers with fuzzy yellow anthers at their centers. Plants also bear smaller-than-typical, dark green leaves that provide a refined look. Also worth hunting down is the Austrian copper rose (R. x foetida), with glowing yellow or burned orange, five-petaled flowers on vigorous, vase-shaped shrubs. Other reliable heirloom roses based on Rosa foetida, including ‘Harrison’s Yellow’ (AKA the “yellow rose of Texas”) and ‘Persian Yellow’, make vigorous, waterwise shrubs for our regional gardens and reach 5 feet. Both Rosa x foetida and R. spinosissima run somewhat and are best in larger planting spaces.
For a more traditional rose look, seek out roses with doubled flowers. A tough, reliable, old garden rose that fits this bill is the autumn Damask (Rosa x damascena nothovar. semperflorens), growing to 4’ tall and wide. This heirloom perfume rose is a hybrid known originally from the Damascus area, which is also the source of its common name. Semperflorens, in its scientific name, references the fact that this rose reblooms in fall, conveniently taking a break during “Japanese beetle season”. Even without roses actively flowering during beetle season, some amount of foliar damage by beetles is likely; most species of roses grow out of such damage without issue, though some gardeners pick the beetles off their plants to
Experts anticipate that, over the years, the gradual arrival of pests that feed on the beetle at various life stages will somewhat suppress the populations of this troublesome insect. For now, our best bets are to employ simple cultural controls, like selecting roses that don’t easily provide sustenance. If motivation allows, we can actively remove beetles during their population peaks each year, or, as a last resort, tolerate the little buggers.