Greenhouse

Jan 29, 2015

Season extension is a fine thing, especially in a climate as hard on farmers and gardeners as Montana’s. The last frost is sometime in late May or early June, and October is usually reserved for preserving what little survives the frigid nights. For vegetables that normally get a head start in warmer climates, such as tomatoes and peppers, a few extra weeks on either end can mean the difference between delicious veggies and compost.

Most greenhouses you might see are big – 20 meters long and filled to bursting with tropical flowers and that lovely earthy smell. Walking in from a brisk outdoors you can feel a wave of heat and humidity wash over you. Anyone who has hopped into a car that’s been in a parking lot in mid-August will understand the concept of how a greenhouse works, but they’d probably also agree that a greenhouse is vastly more comfortable.

Our greenhouse, made by a 2013 FLAT intern out of reclaimed lumber and windows, greenhouse plastic, and recycled road signs, works the same way. It is much smaller, however, housing a wraparound raised bed and several shelves, with just enough room for two people to work. The clear roof admits and then traps sunlight, raising the inside temperature 5 to 10 degrees F above the ambient in the spring and fall. Operable windows cover two walls, allowing ventilation in the summer.

The raised beds, a departure from the traditional shelves normally found in a greenhouse, contain over 3 vertical feet of soil and allow us to choose between raising starts for transplant or raising plants for a full season (those who visited in 2014 were greeted by a veritable jungle of tomato vines climbing up to and across the roof, almost concealing the herb starts perched on a top shelf). In addition, the extra soil mass helps regulate the temperature inside, keeping it a little warmer in the cool season and a little cooler in the hot season.

Underneath the floor another treat awaits: the wooden floor panels lift up to reveal a deep vermiculture pit. Here we have a year-round colony of worms that speed up our composting operation. Every few weeks we mix some food scraps and other compost into one side of the pit and let the worms do their work, retrieving the beautiful soil some time later and switching the compost to the other side to attract the worms. The higher temperatures created by the composting process, and regulated by the additional thermal mass, keeps the worms alive through the winter and adds a little more heat to the greenhouse for the growing season. Burlap and a layer of stones at the bottom help drain excess water and keep the worms from escaping into the ground.

One of the challenges of having this greenhouse is deciding just how to use it – there are so many options! Between early starts for tomatoes, peppers, herbs, flowers, carrots, radishes, and many others, we have to choose which to begin in the greenhouse and which to wait to plant in the garden. We’re also (re-)discovering that vegetables grow differently in the diffuse sunlight and regulated temperature of the greenhouse than they do outside in the garden and ambient conditions. With tomatoes, for example, that means fewer big tomatoes outside or many smaller tomatoes inside.

But, whatever the challenges, the greenhouse has been a great addition to the FLAT. It serves as a demonstration for just how much can be done in a small space with basic, local resources to enhance any home food system.

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