It could be said that there are as many garden types as there are gardeners. I have friends who, with Master Gardener certificates in hand, view the purpose of a garden quite differently than my own. I view almost all of them as legitimate.
For instance, I recently read a delightful book by Laura Simon entitled Dear Mr. Jefferson, Letters from a Nantucket Gardener. Dedicated to growing simply everything in her garden (mostly scores of vegetables) from seed, her “letters” (ie, little essays) dwell on her late 20th century gardening techniques, comparing and contrasting with the third president, a renown gardener of the late 18th and early 19th century. My vegetable garden at Uptop, after a quarter century of increasing shade and a confessed ennui with vegetable growing (all those nearby farm stands… all that produce ready to harvest in August when we are in Michigan), is now called the Parterre Garden, for my only crop these days is a tiny amount of cut-and-come-again lettuces for fresh salads in May and June, the rest a variety of carpet flowers, a few evergreen clipped shrubs, two rambling roses, and lots of tropical elephant ears (Colocasia).
I have two neighbors only a block from me, each highly accomplished and skilled gardeners (one, having published a book on weeds) who have observed the making of Uptop from the beginning. Each seems duly impressed (I modestly assert) by the intensity of the enterprise and the density, breadth – and beauty! – of the collection. However, I think each, being friends, holds (mostly) in bay their horror at some of my resident plants. How could I allow such aggressive/invasive pests?
No gardener should ever sublimate far from their daily thoughts the staggering problems we humans have created for Mother Earth. If we enjoy pushing Hardiness Zones (I do!), there is an underlying and ominous reason it can often be successful. If we enjoy taking a walk in the woods (I do, right behind my house, in a beautiful second-growth New England woodland, punctuated by stone walls laid down by farmers who found greener – and flatter and less rocky – pastures in the Western Reserve of Connecticut, ie, Ohio, long ago), it is also alarming to be confronted, aggressively growing amongst the natives, by what I – and many others – grow in our ornamental gardens only hundreds of feet away. Why and how did they get there? These are unquestionably the invasive species (perhaps aggressive, too) and should not be planted here.
During my time of creating the Uptop garden, the avant-garde of ornamental garden design has been focused on the use of native plants organized in the garden within a “matrix,” drifts being passe in this style. No debate here on this pioneering garden trend which I watch with increasing admiration. And, even as I introduce more natives – especially all the milkweeds to help the beleaguered monarch butterflies – Uptop garden is what it set out to be thirty years ago, perhaps a relic of the rear-garde: a collection of interesting plants from all over the world brought to us by the great plant explorers of the past 300 years, arranged in a way that is beautiful in all four seasons. In this last sentence of apologia, I will add that I tend this garden without fertilizers or chemicals, except a limited application of broad-leaf herbicides on the lawns and a very occasional shot of glyphosate to arrest weeds in the pebble driveway and a brick walkway.
Now, we can move on to the principal topic of this essay, ie, why an aggressive plant can be an acceptable garden choice (as long as the gardener realizes the issues involved in its maintenance) whereas an invasive plant (one that escapes into the wild) is not.
A neophyte creating a garden de novo is highly susceptible, when reading about the dangers of aggressive plants – and, perhaps, ignorant altogether of plants that are invasive – to ignoring this advice. What could be better than covering quickly all that newly available soil? The creator of Uptop – this writer – fell victim and was himself delusional in this regard. Wanting a full and robust planting as soon as possible, I was convinced that such warnings – and there were plenty from friends and from the literature – were for different kinds of gardeners, the timid ones… the ones who sought labor-nonintensive gardens (ie, not me) and valued tidiness above all. A mature 1-acre garden with 1200 species of living plants, no longer needs, if it ever did, a host of aggressive plants. And no garden should host invasive species, period. Sometimes, the two are one and the same. An aggressive plant is the gardener’s choice; an invasive plant must be Mother Earth’s choice. I list here my top six invasive/aggressive species that should never have been allowed at Uptop – and four aggressives that I would not be without. A final word: my aggressives may not be yours, i.e., the vagaries of soil, hardiness zones, moisture, etc, may produce different results in different gardens. But, for the most part, I assume that my invasives will also by yours. My easy definition to distinguish between the two: aggressives spread by roots (which a gardener can control, somewhat) whereas invasives spread by seeds which the wind and birds disseminate.
Invasives/Aggressives, Six to Shun:
Eupatorium rugosum ‘Chocolate’ – An invasive, this beautiful plant has many virtues: thrives in dry shade, easy to grow, fashionable brown leaves with white flowers which in early Fall, brilliantly light up the woodland garden…. But this pest reseeds like no other in my garden (even myosotis); it is simply everywhere, tiny seeds blown hither and yon take root wherever it lands. I relentlessly pull it up everywhere and whenever I can, hauling away cartloads of it to be composted for weeks at a time – and all the while still knowing that I will have it in excess come Fall (when I secretly applaud it). The only other good news here: it is so very easy (like myosotis) to pull up, its roots separating easily from the soil holding it, thus making the innumerable trips to the compost pile light work. This plant was introduced by the illustrious Dr. Richard Lighty, so important in the establishment of Mt. Cuba as the epicenter for the study and display of Piedmont flora, and with every yank I wonder what he must think of it now. Perhaps it performs differently in other areas.
Hedera helix – A long winter of ice and snow takes a toll on this not-always-so-green-evergreen (some cultivars better than others) aggressive ground cover and climber. But the June-September lush new growth is intoxicatingly beautiful and within weeks covers the winter’s expressed weariness. Its leaves bring to mind the laurels worn by Greek and Roman athletic champions or decorations of painted murals in Victorian homes. I have admired it since my youth, remembering how it made a little green lake beneath the pin oak in the Houston home garden of my youth. It also brought a feeling of calm, a relief from the incessant heat, even suggesting a sense of luxe. Years later, now in Connecticut and ready to make Uptop, it was an early must-have for the new garden. The problem: I still have it and in all the wrong places. Naively, I once even decided to contrast the textures of Hedera helix (my old Houston friend) with Pachysandra terminalis (my new Connecticut friend), two aggressive evergreen ground covers. What a mistake, each in a continual war to invade the other’s territory until I ended the war by ripping out all the ivy.
I will not conceal my admiration for ivy-covered mature trees which I first saw used extensively in England in the 1980’s. In fact, Uptop had such a tree when I acquired the property from my English neighbor. I never asked her, unfortunately, before she died, whether the extraordinary ivy growth (the “trunks” of the lower stems are 6-inches in diameter) on this nearly century-old Norway maple were consciously planted to remind her of her native land – or whether, it just got the better of this widow struggling, against the odds of advancing age, to maintain her beloved grounds. I will never know. But the effect is simply magnificent and, as the tree sits near the lane at the front of the garden, it became a signature of Uptop. So much so, that an enlarged photograph of the massive hedera vines was featured on the cover of a garden magazine which included an article about Uptop. An ivy-covered deciduous tree is at its most glorious in winter when the tree almost looks evergreen with it mounds of lush green leaves replacing the fallen deciduous leaves. This scene is all the more spectacular because Hedera helix, once it is about 30 years old, morphs into a different form (the “adult stage”) whose leaf structure changes to a more ovate form and produces a whitish flower in early fall followed by beautiful blue-black berries. Therein lies the culprit: the birds gorge on this feast and their droppings infest the nearby woodlands with easy-to-geminate seeds. But I do not need a trip behind my fence through the dense woodland to see the effect: a common “weed” throughout Uptop’s gardens is the juvenile plant, a few inches high, competing very well against all comers, prized perennials and other weeds alike. Another disagreeable trait of this particular ivy-covered tree: it is located next to the bluestone entry terrace to the Big House and those seeds dropping on the terrace is a continuous maintenance headache. Like all evergreens, Hedera helix does shed it leaves – not all at once – and the Spring fall can be prodigious. Partly because of all this but more because of the massive tree’s age and declining health (and adjacency to our bedroom and the glass conservatory), I decided with heavy heart to cut it down in late 2016. But that is another story: see An Old Tree Dies Hard in a future blog.
Net conclusion: if you must send English ivy up a tree, make it a very sturdy tree far from human activity below – and never use it as a ground cover. Not wanting to abandon this vine forever, I now content myself with growing the many so-called tropical varieties, trained on small tuteurs in the Conservatory. A smart compromise.
Chasmanthus latifolium – Wild-oats is its name and you should not sow them, especially in moist soil where self-sowing is exuberant, to put it mildly. It is overtaking areas that are far removed from the original sin of its planting. It is a handsome display in early-mid October, with its drooping “oats,” but I can no longer look at it with anything but disgust. Its tiny plantlets invade and successfully inhabit every small crack and crevice in the terraces and, of course, in and amongst wood-chip paths and stealthily hiding beneath the largest leaves in the woodland duff.
Euonymus Alatus and Berberis thunbergii – I group these invasives together since both of these genera were existing on the property when I bought it – not knowing then what I was to learn later. The problem here, as in so many invasives (Hedera helix, described above), is the seed, beautiful but fleeting red berries that 1) fall to the ground and root, every single one of them (which is why I have such an inexpensive and beautiful 3-ft hedge of burning bush, or 2) attract the birds who seem to like them, if not love them like viburnum berries, fly off and leave their droppings where they will take root, mostly, it seems, in the nearby woodland.
Houttuynia cordata – Where in the world did I ever get this aggressive (not invasive) plant? Was it sold to me from a Garden Center? Heavens, forbid. It is a horror to be avoided at all costs. In shade, with rich, damp soil, it will take over everything in its path. Improbably, it is actually – if one can adjust one’s knowledge of its invidious ways – a beautiful little unassuming plant with attractive heart-shaped foliage and a pert little white flower with four basal bracts with a terminal spike. Yet, as you rip at it trying to untangle its aggressive white roots from your garden beauties, you will begin to recognize its distinctive rank odor. Maybe there is a place for it in the garden. I would treat it like a bamboo, surrounding it with concrete or metal dams – or, perhaps better, isolated in a container. Be wary of any plant with fleshy white roots.
Lysimachia clethroides – An aggressive to shun, known as Gooseneck Loosestrife or Bishop’s Crook, with its arching crook of white flowers, it is a real beauty… and a beast to eradicate. I have tried for twenty-five years and the damned plant is practically everywhere. It spreads by very aggressive underground reddish roots which dramatically increase, even in winter! Uptop was started in 1993 when I relocated from my earlier garden around the corner, in the flood plain of Long Island Sound (down below) to my new fifteen-feet-above-sea level “mountaintop” (up top). Working carefully not to include any of those tell-tale red roots in any of my transplanted perennials, I obviously failed and within a year, the new garden started to exhibit this charming beast. Had I known what was to come, I could have easily eradicated it (as with Houttunia cordata) by painting on glyphosate. Again, it might be incorporated into a flower border if the roots could be completely restrained, accomplished with difficulty and, I suspect, limited success.
Four Aggressives to Love (Worth all the trouble, in spite of all the work):
Ajuga reptans – Perhaps its common name (carpetweed or bugleweed), warns us away but I find this low ground cover very useful and, when in bloom in May, a quite colorful addition of glamorous blues. I use it prolifically at the front of the double border at Uptop and in the Ericacious Walk as a path for walking on. While its dense matting will not root out all weeds (what will?) it does a tolerable job at this. More important, I find the inches-high scale extremely helpful in setting off – even showcasing – the taller perennials behind. I prefer Burgundy Glow, the leaves of which emerge a dark purplish-green, become ratty after the two-week spring bloom, soon regain their vigor. It grows by sending out near-surface roots with profligacy, making it easily transplanted, but also it is those roots that must be edged back from territorializing too much border real estate or running right into the adjacent lawn.
Pachysandra terminalis – Not only is this a non-native aggressive ground cover, it is also dreadfully common. Used by land-scrapers all over the northern hemisphere, serious gardeners shun it in favor of the Appalachian Mountain native Pachysandra procumens, which I find dull and a bit frightful in its winter dormancy. Once established, there is hardly a more beautiful ground cover than Japanese spurge – and it is evergreen even under snow! Few ground covers are more carefree under a large tree, so much more effective and beautiful than Hedera helix which breaks its ratty winter dormancy very late. Its use in large fields is particularly attractive and clipping those white aggressive underground roots at its borders is not really much work with an edger. The cultivar ‘Green Sheen’ is a real star. The commonness of this ground cover repels garden aficionados but not me.
Petasites japonicus ‘Variegata’– This huge-leafed water lover spreads like wildfire, but what a lovely “pest” it is. I rue the day when its spread invades its nearby neighbors but for now, it is an eye-catcher in the garden and I stay ahead of its stealth. My planting is not near water (for I have no water, sadly), and yet its aggressive behavior seems undiminished. I can only imagine if it were at the edge of my dreamed-for stream.Sasa veitchii – Beautiful in summer, extraordinary in winter when the leaves develop a bi-color arrangement with straw-white edges. This bamboo runs (and fast after it gets settled in) and I would be tempted to just let it run – it is that beautiful – if I had more space and better boundaries. The Brooklyn Botanic Garden does it right: large monoculture at the edge of the Japanese Pond, and bordered by concrete bulkheads, walks and curbs. At Uptop, I keep it in bounds, after 15 years of constant root clipping, with a concrete dam just under the surface of the 12-ft. diameter planting. So now it is restrained as has been from the start the Phyllostachys aurosulcata within a 2-ft deep x 1-ft wide concrete dam at the rear of the property. Meanwhile, my other bamboo, two cultivars of fargesia, are among my favorite plants in the garden, so effective as a border visual barrier and so green all winter long – and it clumps, not runs.