We do not have local information on underground greenhouse construction and uses, but are you interested in the structure for home use or commercial use (like a cut flower, herb, or other business)?

Greenhouses in the broad sense are varied structures built to accomplish different things, from protecting semi-tender or mostly-hardy plants from the brunt of winter weather (like a hoop house or cold frame does) to housing tropical plants intolerant of cool temperatures (like a heated conservatory). Your goals for using a greenhouse will dictate which type of structure best suits your needs, and therefore how to build it and what plants it can accommodate. Goals can range from simply starting vegetable or flowering annual transplants to get a jump-start on the growing season, to season extension (to keep producing a harvest just a bit longer into the autumn), to year-round food growing, to overwintering (or housing year-round) tropicals like citrus, jasmine, Ficus, and Philodendron.

Here are some other Extension resources that provide detailed information about home greenhouses:

• The Hobby Greenhouse - Oklahoma State University
• Hobby Greenhouse Design Notes [PDF]
• Hobby Greenhouses - University of Georgia Extension

If your goal is increased food production by way of shielding crops from cold in early spring and late autumn, you can use a small high tunnel or greenhouse. Either one can be a DIY project or purchased as a kit. In comparison, a greenhouse is more permanent and will need to be ventilated with a fan and probably heated (even if partially or fully sunken). You can also find how-to videos by searching the web for "garden" and "high tunnel" along with search results narrowed to ".edu" pages.

• Starting a Garden: Season Extension - Illinois Extension
• Extending the Garden Season with High Tunnels - Penn State
• High Tunnel Construction [PDF] - Mississippi State Extension

The simplest use of a greenhouse would be to consider it a large "cold frame," which are unheated structures meant to shield young seedlings and transplants from the brunt of the cold while allowing them to acclimate prior to planting outside. Otherwise, you can heat a greenhouse to accommodate cold-intolerant plants, but that tends to be expensive depending on how well insulated it is along with the type of heat source. Seed starting may also benefit from supplemental artificial light, depending on the plants involved and what time of year the process is begun, and this can be difficult to provide in a greenhouse where temperatures and high ambient humidity may impact the performance of the light fixture.

How cool the plants prefer to get will also determine what type of structure makes more sense. For example, potted Rosemary, citrus, and flowering Florist's Cyclamen do well with insulated but cool conditions during winter where they might experience nights in the upper 50s, but Alocasia, many members of the African Violet family, and basil should not be chilled to that degree.

One other aspect to keep in mind is that natural daylight in the winter is not long enough or intense enough here for most plants to continue growing, whether they are decorative plants or those used for harvesting foliage (like salad greens) or fruit (like tomatoes). So, while plants may stay alive when the right temperatures are provided, they tend to stagnate in size and not actively grow (or may grow very slowly) until spring. For plants that don't have very high light requirements, the use of artificial light to supplement natural light might allow them to grow or bloom during this time, but it will be difficult to supply plants requiring strong light (like tomatoes again) with enough light energy and daylength for them to continue bearing crops. The reduced natural light will be a greater challenge with a sunken structure, since that further limits how much sunlight will reach the interior since it can't enter through the full height of the walls.

Miri