Building Raised Garden Beds in your Hoop House

by Stacey Cooper, Organic Garden Manager

Raised beds can be built and back-filled with a variety of materials.  It is usually handy to utilize materials you have access to on site or at your home.  Some examples of reclaimed materials that you can utilize to help keep expense down are concrete blocks, untreated barn boards, re-bar, sand, compost, or topsoil.
I choose to use wood to build the raised beds in the Shaker Organic Garden hoop house largely because access is an issue in the winter and spring months.  Concrete blocks would have been a chore to get on site, while lumber could be carried to the greenhouse by hand or with the tractor.  To facilitate using the tractor to move materials, I pre-cut the lumber into 6' lengths. This helped in a few ways: I was able to fit the lumber in the tractor bucket to move it, the shorter lengths allowed for more flexibility with the varying grade of the hoop house floor, and it readily marked where 25% were needed to stabilize the lengths of the beds.
I chose to construct the beds at 3' wide, which is about a foot more narrow than the average raised bed.  I choose to do this because it is easier to reach across for fertilizing, weeding, and harvesting without needing to rest my arms on the soil surface, which can lead to compaction. 

I also set the raised beds in about 2' from the outside edge of the hoop house. This allows the outer area to be used as an access path. The outside strip of soil around a hoop house collects the run-off condensation that is produced inside the house and leads a strip of soil with leached nutrients.  This outside edge is also the first to freeze and last to defrost.  By setting the raised beds in a little, I am able to use the least conducive soil for access and the best for growing plants.
The weight of growing medium along the length of a raised bed can cause the boards to bow out and eventually break.  By placing stakes or rebar hammered into the soil, every 6' or so, we have alleviated this pressure.  I prefer to place stakes on the inside of the beds.  This allows easier weeding and cultivation of aisles and also keeps clothing and equipment from snagging on the sides of the beds when working around them.

To backfill the beds I used some onsite loam, stockpiled from the existing floor of the hoop house that accumulated from grading and leveling the area along with compost, sand and greensand.  The approximate ratio for the 10" beds was 2" of loam, 2" of sand, 5" of compost and then appropriate amounts of greensand to improve drainage and prevent clumping of the compost. A bit of balanced organic fertilizer is all that will be needed to get seedlings or seeds started in the beds.
The first crops I plan for these beds are beets, peas (for tendrils), and radish.  The heating system is not yet operating, so getting seedlings going and planting them is risky. I've selected cold hardy direct seeded crops to start the season to better utilize the space.  In a few weeks mizuna, lettuce, pac choi and kale should also be ready to transplant.
I have a few early season flats that were in need of sunlight, but not ready for the cold nights in the hoop house.  I experimented with digging out a section of the raised beds, placing the flats into the channel and then placing an on site Plexiglas door over the flats, creating an improvised seedling chamber. So far the experiment has worked as the seedlings were left in the chamber over the weekend and seem to be growing fine.  The mizuna and lettuce seem to be responding the best.  Since this system seems to be working I will get a few more flats seeded this week and move them to the chamber once germinated.
One of the most gratifying components of small scale farming for me is the constant need for improvisation.  Using what is on hand, creating new processes and sometimes finding success makes for a good days work!