I hadn’t thought much about this question until beginning work as the manager of the Ketchum Farmers Market in Idaho. When farmers spread out their wares come opening day in June, it still took me a while to understand why the selection remained focused on salad greens, radishes and other early-Spring plants. I figured that they all would have greenhouses and be growing starts starting in February or March.

But such was not the case, although many of them have built greenhouses, or increased the efficiency of previous constructions, thus enabling them to produce crops for an extended season. I’m just getting started with my own here in Pennsylvania and thought it would be a good idea to drop in on the Mt. Cuba class.

So, why have a greenhouse? They help you control light, temperature, water (humidity) and air. Badda bing: your own microclimate. The structures I saw at Mt. Cuba consisted of framing, covering, vents, heat (pumped in from boilers in another room, cooling, thermostats, max-min temperatures, air exchange, fans, water availability and quality, alarms and back-up systems. I’m personally not going for the 4 a.m. alarm in my closet letting me know the heating system has failed.

The greenhouse employees at this DuPont estate focus on cultivating plants native to the Piedmont region, which extends from New Jersey to Georgia. They also cultivate plants for display in appropriate areas around the estate. Others may gather seed for the greenhouse people to propagate. Careful notes are taken to establish the collected seeds’ provenance.

They have enjoyed great success using cone-tainers to start many native plants, especially as these containers promote good drainage. I also learned about the importance of moving air – it keeps bacteria and fungus away to a large extent, as well as minimize microclimates that can change how plants will mature from one side of a table to another. Further, plants need air exchange; they do not just want to sit in stagnant tanning bed air.

Phil Overly, our guide and the head propagator (an extremely accomplished orchid propagator), prefers glass to plastic any day, although the Center’s 9 are constructed from polycarbonate. He also prefers clay pots to plastic, as they breath somewhat. Salts from fertilizers will build up on them though. He also recommended closing up the greenhouse in the heat of summer – when nothing is being grown inside – to roast the heck out of any bugs and such that might still reside in there.

The staff use green shield to disinfect pots, making them clean for next cycle’s use. For potting, they work with a variety of recipes but generally always employ Sun-gro metromix 560 with Coir and amend it with varying amounts of root aid (from Down to Earth Distributors), lyme, New Zealand sphagnum moss and more.

Books on the potting table: Native Trees, Shrubs and Vines by William Cullina; Native plant propagation by Jan Midgley; Growing and propagating wildflowers by William Cullina; Reference manual of wood palnt propagation from seed to tissue culture by Michael Dirr.