Goldenrod, a Lovely Garden Thug
There are nearly two dozen Solidago species in the Midwest flora and all but one are native -- the exception being the interstate goldenrod. Yet, while I enjoy seeing goldenrods enliven the late summer and fall landscape, I do not want most of them in my flower beds. They are invasive, especially tall and Canada goldenrod (S. altissima and S. canadensis). Goldenrods can reproduce by seed but they also are especially good at making colonies asexually (i.e., vegetatively) by shallow spreading rhizomes. These rhizomes are easily distinguished from the fibrous roots, radiate from the base of the stem, are much thicker and firmer, and usually at least somewhat lavender or violet. A robust plant might produce 10 or so of these offshoots every year after established. The offshoots can in turn do the same. The power of compounding. Moreover, goldenrods in general are remarkably tolerate of human disturbance which contributes to their weedy potential. -- The plant police will take issue with my use of the word invasive in association with goldenrods. I did it just to rile them. The police reserve the more severe sounding adjective invasive for exotics, that is non-natives, and instead use the term aggressive for native taxa that behave the same way. This distinction, essentially ecological grammar -- think may v can -- is lost on most people.
Like oaks and maples, goldenrods are perennial (i.e., capable of living more than two years) so to eradicate they must be pulled. Attempting to do so when the ground is dry and hard can be difficult thus ineffective. My strategy is to remove almost all of them from my manicured beds -- the younger they are, the better. Instead I enjoy them in the wildlife corridor I promote along the sunny stretches of an intermittent stream that meanders through my property -- sunny because I periodically remove most of the woody plants that appear there. The goldenrod stems, which can sometimes reach 8 feet tall, look better in this more natural setting. I prefer the mixed species arrangement this promotes (i.e., with ironweed, cut-leaved coneflower, cup plant, etc.) but I also do some editing there as goldenrod is a thug. Goldenrod will take over if you let it. I try not to let it and am selective about when I do the culling; e.g., when the ground is moist and never when the floral display (the fireworks, technically referred to as anthesis) is happening, but I do the removal before seeds have developed. FYI, 'Fireworks' is an attractive cultivar of rough goldenrod (S. rugosa). I will repeat, since goldenrods are perennial, you must get the subterranean portion with the rhizomes. Cutting the stems is NOT an eradication action. Furthermore, if you attempt to eliminate goldenrod with herbicides you are both foolish and ignorant and would still have to deal with the substantial dead and nearly woody stems. After the growing season is finished, the stems naturally die, gradually turn brown-gray, and separate by decay from the subterranean part of the plant. One of my winter chores is gathering these stems, along with those from other similar plants, and disposing of them in my boulder ringed fire site.
Goldenrods belong to the sunflower family (the Asteraceae AKA Compositae). It is one of the biggest plant families. There are more than 300 asteraceous species in our midwestern flora (i.e., naturalized plants, species that are able to survive year round outside). About half of this total are non-natives and a high percentage of these are weeds. Some members, because of the fact they can pierce and cling, are both unwelcome and unpleasant (e.g., burdock, beggar's ticks, cocklebur, Spanish needle, and most thistles). Want to get to know the composites better? I recommend you give a look at The Sunflower Family in the Upper Midwest (Antonio & Masi). Published by the Indiana Academy of Science in 2001, this 421 page case bound book features all the genera and the majority of our species, with nearly 500 full color photos including very useful in situ shots. Full disclosure: I was the editor and production manager of the book. Moreover, all goldenrods are insect pollinated. The beautiful, numerous, clustered small rayless "flowers" attract a wide variety of nectar-sipping species. Related, goldenrods only connection with hay fever (allergic rhinitis) is seasonal concurrence with the condition and the wind dispersed pollen and spores which are to blame, yet the "cause" myth persists.
Native plant purists often are reluctant to badmouth goldenrods (i.e., remark on their thuggishness). If these zealots garden they cannot help but realize that goldenrods can be a problem but the fact that the genus is almost entirely native in the Midwest causes them to temper their remarks. A conundrum. Too many people presume or have been convinced that ALL natives are good and ALL non-natives are behaviorally bad, and that only native plants will attract insects. Balderdash! In late summer go to any garden that has Caryopteris (bluebeard), 'Autumn Joy' stonecrop, or Heptacodium (seven-sons), for example. All are non-native to North America, and all are insect magnets.
I was a co-founder of the Indiana Native Plant Society (INPS, formally INPAWS) and know this -- many weeds are native. For example, in addition to goldenrods, Rugel's or red-stalked plantain/buckhorn, sweet autumn clematis, carpetweed, ragweed, purslane, pink weed, common evening primrose, wild grapes, common peppergrass, marestail, dogbane, trumpet vine, boxelder, silver and red maples, cattail, Virginia creeper, blue or honey vine, numerous grasses, common violet, et cetera. Get the idea? Good v bad, desirable v undesirable involves more than nativity. The label native can be an important consideration, but it is only one factor, a designation that in many ways is meaningless, especially when making the "native" claim based on state or province, the boundaries of which are almost all artificial and geopolitical. For example, plant nativists in Fort Wayne (IN) would claim as "native" a species found only in the Evansville area despite the fact that unglaciated Vanderburgh Co. (Evansville) is 300 miles SW from glaciated Allen Co. (Fort Wayne) never mind the variation in substrate and climate. Native is often something like team Indiana, a tribal thing. At the same time the cultists will frequently exclude (refuse to consider native) a species not found in Indiana but whose closest locality is south central Michigan (50 miles N) or northwestern Ohio (18 miles E). This is unsound reckoning and biologically absurd. Nativity is a complex topic -- not always only binary as many want to think. Moreover, consider this real article title, Tips For Killing Weeds in a Native Plant Garden. (See lead sentence) The author's response might be: "you know what I meant," to which I might reply, "perhaps, but I know you are confused. It is an ignorant title but I doubt you will change your way of thinking because that is just what we do, or should I say don't do, most of the time." Conditioning, illusory truth, and blind bias. Besides, we like to keep and protect "our own" stuff, both things and ideas, sometimes even when they are broken. And, not surprisingly, since most of us are change averse, even when a better option is readily available. You might consider reading my rant for next month in which I will point out gardening impediments like GULLIBILITY, DENIAL, and IGNORANCE.
A final thought -- goldenrods should be kept in check, but boy are they beautiful in September and October. Afterwards, consider pulling at least some of them, especially those primed to take over your beds.