Monday, March 10, 2008

Bathing with Orchids

I’ve been gardening for at least 35 years now in some fashion, and I’m still learning as I go. If asked to name the most difficult aspect of the pursuit, I would put watering at the top of the list. It sounds like such a simple thing, but there are so many variables involved that one nearly has to develop a “sixth sense” over time in order to avoid what I believe is the number one recipe for gardening disaster, especially when growing in containers – overwatering.

I think I was lucky to begin growing epiphytic orchids at an early age, since there’s no better illustration of the way that plant roots function in (or even out of) a pot. Epiphytes in nature grow perched on tree branches, rocks, and even fences; included are plants from many families, notably orchids and bromeliads. Most of them are tropical in origin, although some (Spanish moss, for instance) do range into zone 7 on occasion. Their roots are designed to absorb water as it rushes across them, so they tend (and even this varies according to variety) to resent any potting medium which holds moisture against the root system for any length of time. These plants respond best to very high levels of ambient humidity, and would prefer to be inundated daily, as long as the roots can shed the water within a couple of hours at most. Some of mine are mounted on cork slabs or sticks of wood, with the roots totally exposed, and some are merely attached to wire hangers, with their roots dangling freely into the air.

The most extreme example in my collection is Angraecum sesquipedale, a monopodial (meaning it grows somewhat vertically from a single main stem) orchid from Madagascar which, many years ago, burst out of the clay pot in which it was growing. The pencil-thick roots now extend a good 3 feet below the ruins of the pot, and it produces 5 or six enormous, fragrant flowers at this time every year. It’s famous because Charles Darwin, on seeing the 18” (hence the Latin specific name), nectar bearing extension on the rear of each bloom, hypothesized that there must exist a nocturnal (this because the flowers are fragrant only at night) insect (it turned out to be a moth) which possessed a proboscis long enough for the orchid to have evolved in partnership with it as a potential pollinator. Mine is famous, in my house, at least, for being the only one of several hundreds of plants with which I shower on a daily basis while it’s in bloom. This is necessary for two reasons: my housemate loathes the sweet, but overpowering fragrance emanating from the blooms after sundown, so that it’s moved into the shower stall of my bathroom every evening before dinner; and dousing them is the best way to saturate those rope-like roots inside the house. Seeing me naked does not seem to have traumatized the plant yet, but I’m really glad it can’t talk, just the same.

At any rate, it has occurred to me in the last few years that almost all plants are epiphytic to some degree, in that the roots have a need for oxygen. Translation: it’s all about drainage. Realizing this has helped me to improve the growing conditions in our heavy clay soil as well as in the numerous containers I tend. I hoard perlite, oyster shells, and granite chicken grit for ramping up the drainage in potting mixes. The chicken grit I sometimes haul all the way home from our visits to western Pennsylvania, since it’s hard to locate here; ironically, it’s shipped there from North Carolina. I’ve also learned to add lots of extra drainage holes to pots, and not just on the bottom. Holes in the bottoms of pots are great, as long as the soil under them allows the water exiting said holes to run out, but if they’re sitting on clay, as many of mine are, holes drilled on the sides of the pots, near the bottom, are much more valuable. I tried covering these holes with landscape cloth, in order to save potting soil (a large percentage of the household budget goes in that direction), but even this caused pots to retain too much water for many plants. I’ve decided that even though some potting mix may eventually be lost to erosion, most of it will still end up on our property in some form.

I tried putting some scraps of plastic lattice under my stock hellebores, which are grown in four gallon plastic nursery pots, last summer, and found that this greatly improved drainage and aeration, thus resulting in many fewer plants being lost to “summer blight”.
As mentioned in a previous post, I’m experimenting this year with permeable fabric planting bags for hellebores and peonies, plants which require outstanding drainage to survive the summers here. I’m also installing water barrels to allow for the additional water I expect these containers will require, since moisture will hopefully evaporate from the entire outer surface of the container.

I was excited for a while about the availability of (very convincing, visually) fiberglass and foam half-barrel planters, and I now own dozens of them in various sizes. Unfortunately, they haven’t proven to be the perfect vessel in which to create mobile gardens. Although fiberglass will not break apart when it freezes, as does terra cotta, or rot away over time, as do half barrels, it just doesn’t “breathe” the way that clay or wood do. Some things do fine in these containers, especially after a major attack with the power drill on the sides last spring to create extra drain holes, but others are not faring as well. I’m in the process of hunting down real half barrels again, and pretty unsuccessfully, too, I have to admit. I’ve even discovered that their eventual deterioration may prove to be an asset over time. Deciduous azaleas are not at all fond of the clay in our yard, but they’ve done well for several years in half barrels. By the time the container rots away, the azalea has formed its own root ball which sits high and dry above the surrounding ground level (rampant Vinca major basically hides and shades the root ball). These plants appear perfectly happy to be growing in their own little “hummocks”, with only the base in contact with the actual native soil. This is high planting in the extreme, but it seems to work pretty well for anything susceptible to Phytophthera and other diseases, including Daphne, Gordonia, and Camellia.

A large percentage of my garden is growing now in identical 4 gallon black plastic nursery pots, which allows me to make the most of my small garden in that these can be rotated in and out of view as they come into bloom or growth. They're either nested in larger clay, fiberglass, or plastic planters (since all of the nursery pots match, they can be lifted in and out without disturbing the other plants in the larger containers), or concealed by the surrounding vegetation (out-of-control vinca, euphorbia cyparissias, and, yes, honeysuckle) or mulch. I'm still working out exactly what can be partnered in these containers - last year's major discovery was that South African bulbs (such as Eucomis and Galtonia) coexist well with tuberous gesneriads (Achimenes, Eucodonia, and Seemannia, for example), in that they both want moisture and light in the summer, but dry, cool winter storage. By grouping plants with similar cultural needs together, I don't spend hours every spring repotting each container. Seed grown Formosa lilies will share pot space this summer with red okra, which will cover the "bare knees" of the lilies and provide color and foliar contrast (not to mention ingredients for jambalaya). Dozens of pots containing daylilies and narcissus are coming into bloom in every odd corner of the yard right now; this is an idea I borrowed from the New York Botanical Garden, which has an enormous walk bordered by a combined planting of these two genera. Camellias can spend several years in these nursery pots, and it's a good thing, since I love to grow them from seeds and cuttings, and have amassed a huge collection over the years. One day, when I inherit a plantation, I can plant a camellia maze like the one at Magnolia Gardens outside Charleston. I wish I could say that I have (or take) the time to change out these pots as often as I'd like, but it's still easier than repotting gigantic containers three times a year.

So why do I grow all of these plants in containers anyway? Other than the aforementioned soil and drainage issues, there’s a nagging little voice in the back of my head that still wants to live on a much larger piece of land. I doubt it’ll ever happen, but if it ever does, I want to be able to take as much of my garden along with me as possible. After all, how could I even think of parting with a bathing partner of 15 years?

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