When I was a child, hemlocks made a big impression on me. Deciduous trees dominated in our yard and in most woods that I regularly played in with my sisters. Evergreens seemed special and magical whenever I came across them. A hemlock grew just off the porch at my grandparents' house, creating a mystical, shaded place, and providing compact cones that we collected and used as money, livestock, food--whatever our make believe games required.
When my parents took us to visit the deep, hemlock-filled gorges of the Hocking Hills, they seemed to me like something out of a fairytale--cool, fragrant, and inviting after the scorching heat of the parking lot on a summer day. Though their needles were delicate and fine, the hemlocks appeared incredibly tough as they towered over the trails, some seeming to grow directly from the rocks. I was left with a lasting impression of these trees as rugged and vigorous.
Years later I learned of the difficulties homeowners experienced in trying to get hemlocks established in their yards. The trees had a reputation for needing soil moisture to be just so. The merest hint of sogginess and the trees declined and expired before the end of their first season. A veteran of the landscaping industry explained to me why this was so: When trees are grown for sale, the individuals that thrive under the conditions of commercial propagation would naturally be chosen to be further propagated. At some point plant developers stumbled upon an individual whose seeds sprouted very quickly for example, or whose cuttings had a high rate of rooting success. Understandably, this superstar was propagated like crazy, so its genes came to dominate in commercially grown hemlocks. Unfortunately it was apparently more picky about drainage than a typical hemlock, and this trait was passed along as well. Because of this fast track evolution that plants in the industry undergo, they are different from wild specimens, and may behave differently.
The difference between natives and nativars is well know among native plant enthusiasts. Most of us are aware that nativars, or cultivated varieties of native plants, might not provide the ecological services that straight species offer. The modified foliage color, or flowers of different sizes, shapes, and shades, are simply not recognized by the native herbivorous insects that would ordinarily visit for pollen, nectar, and leaf munching. Fewer herbivores lead to lower populations of insectivorous birds and other animals, affecting the entire food web.
If you are interested in planting natives as a way of supporting wildlife, you can seek out straight species plants where they are available. Insects will recognize them as appropriate food sources and be able to get sustenance from them. However, nursery grown plants can have visually unobservable characteristics that make them different from wild due to the pressure of cultivation, as with the case of hemlocks. An unnamed variety of hemlock labeled as simply Tsuga canadensis purchased at your local garden center, will not be the same as one found growing wild. (I am by no means advocating for visiting wild areas to dig up plants for your garden.) I find it useful to think of any commercially propagated plant sold as straight species as an unnamed cultivar, to acknowledge that it might differ from its wild counterpart. I assume that as long as it is visually the same as the native species, it will attract and support wildlife equally well, but may require special care to get it established due to differences that arise under nursery conditions.
Another consideration when planting nursery-grown stock is that even if the plant is genetically identical to a wild plant, the pampered lifestyle it is accustomed to is radically different from life in your garden, and it will take time to adjust. Regular infusions of synthetic nutrients and water into its growing medium make for lush foliage, lots of blooms, and often a strong but tangled root system. Such plants may require some TLC as they ease into the real world of soil and natural rainfall. It's a process akin to an addict getting clean and living a healthier, more balanced, lifestyle.
It's important not to make assumptions about a plant's natural characteristics based on experiences with nursery-grown plants for the reasons I've explained above. Observing plants in the wild is the best way to understand their habits and preferences. However, here is something to keep in mind: It's an often unacknowledged truism that plants do not grow in spots that they like best, but in sites where they can best compete. This fact explains why understory trees can sometimes be grown in full sun in your yard. Such trees have exploited the space under the canopy because they can survive in shady areas, but they hey harbor the ability to live in full sun and often explode in size when given the opportunity. I'm witnessing this phenomenon with pawpaws growing in full sun as they colonize an abandoned field. This also applies to trees that grow on cliffs in thin soil or species often found in soggy riparian zones. You don't always have to recreate such conditions to successfully grow these trees at your site. A moist, well-drained soil amended with compost--in other words, a perfect, generalist spot--will often suffice.
One more thought before I end this meander: I've been working to create the condition I just described--moist yet well drained, rich but not too rich--in the potager for decades. Its soil is well-structured and abounds with life. It is a perfect spot for seeds of many types to germinate and thrive, which leads to lots of weeds, since the garden is surrounded by woods and fields. The weeds indicate, not a problem as is often believed, but a haven. I'm doing something right and nature is lurking and will turn my garden into forest in short order if I let her. I'm not working against nature; I've merely borrowed a plot of land to provide for myself and family for a brief moment in time. It will be returned someday in a fertile and productive state for her to do with as she will.
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