Season Extension
What is a Greenhouse?
When it comes to extending the growing season in Maine, greenhouses, hoophouses, and high tunnels are invaluable tools for gardeners, farmers, and plant enthusiasts alike. The differences between greenhouses, hoophouses, and high tunnels can be muddy, but generally, a greenhouse is a structure typically made of glass or transparent plastic that is designed to let in sunlight, creating a warm and controlled environment for plants. Greenhouses are often heated (usually with electric or propane systems) to maintain an optimal temperature year-round, making them ideal for growing plants that need consistent warmth, especially in colder climates. Unless specified, we use the term greenhouse to encompass all of these systems.
Here at Whaleback, we have two hoophouses, a simpler, more affordable version of a greenhouse. Ours are made from cattle panels bent inside a wooden frame with plastic sheeting overhead. These structure are unheated, relying on solar gain and passive heating to maintain warmth inside. Hoophouses are mainly used to extend the growing season during spring and fall, but we also use them to overwinter some tender perennials such as Figs and Rosemary plants.
A high tunnel is similar to a hoophouse but tends to be larger and more durable. High tunnels are also unheated and rely on natural sunlight and passive heating to warm the space. The higher ceilings and greater height allow for more airflow and greater plant variety, and they often feature roll-up sides for ventilation. Like hoophouses, high tunnels are generally used for season extension and improved crop protection.
Why Build a Greenhouse
As we mentioned, in colder climates like here in Maine, greenhouses can be invaluable for producing crops and vegetables both earlier and later in the year than would be possible with in-ground plants only. Even in our unheated hoophouses, we can start producing cold-season crops like spinach, arugula, radishes and bok choy in Mid-March, nearly two months earlier than we could in our outdoor beds.
During the peak summer months, we use our hoophouses to exclusively grow hot-weather crops such as okra, hot peppers, and ashwagandha. Once these plants begin to die back in the late summer, we can usually get one last round of cold-weather crops to grow before the deep winter freeze sets in. Even during this frozen period, we have fig trees planted in the hoophouse that are able to overwinter with a thick layer of mulch. A winter greenhouse is also useful as a space for chickens to escape harsh winds and to store stratifying seeds (as long as they are kept moist/frozen).
Issues with Greenhouses
Like any system, a greenhouse has unique challenges, first and foremost, the lack of rain. Some well rooted plants will be able to tap into soil water if it has been a rainy season, but for the most part, greenhouses will need to be irrigated. This can be done by hand, with a watering can or hose, or with a more permanent system like a sprinkler or drip tape. In our small hoophouses, we have had success drilling holes into old hoses and threading this between the plants as a low cost drip tape alternative.
Greenhouses are also prone to fungal diseases like downy and powdery mildew. These diseases are exacerbated in places with stagnant airflow and close plant spacing, which tends to be the case in greenhouses. One way to prevent this is to have some form of ventilation even in the simplest greenhouse. In our hoophouses we have a roll-up back side and can prop the door open which facilitates a cross breeze.
How to Build a greenhouse
We are often asked how hard it is to build a greenhouse, and this question really depends on the size and scope of your plans as well as your experience with basic construction and tools. Building the hoophouses on our farm only took about two days each and less than $300 in materials. The overall design is quite simple and robust. That being, said we learned a lot between the first and second build and made many design changes and plan on making more for any future hoophouses.
If you run a commercial farm or enjoy large scale gardening, investing in a larger greenhouse or high tunnel from a kit can be a great option for expanding your growing capabilities. These kits provide a comprehensive solution, often including the frame, covering materials, and necessary hardware. However, even with instructions provided, there are still many factors to consider when setting up a large (or small) structure. The ideal orientation for maximizing sunlight exposure, proper wind protection, and effective drainage are all critical to the success of your greenhouse or high tunnel.
If a greenhouse, hoophouse, or high tunnel is what you're looking for, we can work with you to determine the best fit for your specific needs. We can assist with everything from site selection and preparation to full installation, ensuring that your greenhouse is ready to brave the Maine winters and provide food for you for years to come.
