So what is a weed, after all? I believe it was Emerson who stated that a weed is a plant whose virtues have not yet been discovered. It seems that this future virtue will be in the eye of the beholder. I once grew out a lawn (meaning I did not mow -to the neighbor's displeasure) around a house I had rented just to see what would rise up. I had cataloguedd seven flowering plants in the lawn that summer or, to the neighbor's eye, seven weeds. I am no enemy of plants so that certain "volunteers", as my grandmother calls them, are always visible in my garden. Fortunately, this means little to my Brooklyn neighborhood, where weeds and garden plants seem to equal each other in number. Weeds are the green mass around the mass of concrete.
I allow, in my current garden, a selection of weeds that I feel I can manage, namely Dayflower Commelina Communis and Smartweed Polygonum caespitosum. They self-sow each year, have pleasant visual attributes, and are easy to pull should they get out of hand. I allow them to fill in blanks the way another gardener might with annual seeds bought at the garden center. Now I must admit I also have a knack for picking perennial plants for my garden that become "weedy." It took me two years to eradicate plume poppy Macleaya cordata from the garden. At times it seems that everything I like is weedy in the garden: Solidago, Spiderwort, Perennial Ageratum, Maximillian Sunflower, and Boltonia. It has become a matter of learning how to manage these perennials so that they do not behave like weeds. So even cultivated plants become weeds in the garden, and often they do so out of the garden.
Do we think the same of a weed that pushes through our sidewalk as we do of a weed in the garden, farm or park? I think the context with which you engage these plants gives them their offensiveness or virtue. For instance, if you are trying to tackle a weedy back lot that has not seen sustained attention in years, you will curse the perniciousness of certain plants till your death. A friend in Williamsburgh, Brooklyn has been battling morning glory vines since they moved into that house 11 years ago. Decades of seeds sitting in the soil, simply waiting for the right stimulus to sprout. Weeds to the farmer hit his bottom line, infiltrate his harvest, and so are cursed, yet some commercial crops are weeds themselves. In parks, especially wilderness parks, the weeds are often called "invasives" or "aliens". Yet the native plants found in many parks may be considered weeds to the farmer or in our home garden. As a way of distinguishing, maybe it is that weeds seem to inhabit our most cultivated landscapes, whereas invasive plants inhabit our natural places. No matter, because all these plants have the ability to adapt to and exploit their new environment. Some will be weeds in your garden and some invasives will be your beloved garden plants. What's a gardener to do?
We have to make choices for our gardens. It’s worth checking online lists of weeds and invasives so that you can make informed choices, learn about the habits of these plants so that if you do plant them, you may try to keep them under control. The New England Wildflower Society has a great website with lots of information, including their definition of native, exotic, and invasive plants. (Update: There are many lists now available by simply searching the Web with a search engine.)
Certain plants are illegal to cultivate in certain states and often these will not be for sale in those states. I have not found a listing of illegal plants for New York State (at time of publishing), but state government has established a council, the Invasive Plant Council of New York State (possibly defunct as of 2022). I believe, as in some other states, that sales of certain garden plants (ex. Purple Loosestrife, Japanese Barberry) will be made illegal in the state of New York. A list has recently been put together by Suffolk County.
Ultimately, I have mixed feelings about the whole issue. Weed versus cultivated plant, native versus alien invasive. I am concerned about the ecosystem disruption brought on by the non-native invasive plants. It has become a landscape management crisis. However, species do migrate on their own and as companions to other species (like us). When we think about this, we need to understand that it is human need and desire that creates both invasive plant problems and native plant conservation. We want the native flora to flourish and to have our cultivated plants. How can we choose? Should we?
loosestrife