Vegetable Growth in the Winter

Hi there,

I live in Zone 5 in MA and am helping start up a greenhouse this spring. The owners of this greenhouse would like to continue growing vegetable throughout the winter to harvest and we plan on insulating it and using passive solar heat as best we can. However, we are also looking to invest in a heater just in case. With that said, would I need to have artificial lights in place to promote the continual growth of vegetables so that they can be harvested over winter? We are also hoping to invest in some heating mats which should lower the overall heating cost of the greenhouse - have you had any experience with those?

Thanks for your help.

Doug says you don't say what kind of vegetables you want to grow. If you're talking about low-light crops such as kale, spinach etc then you may very well get through without any supplemental lighting. You won't get a high growth level in Dec-Feb but if you have the crop well grown by then, you should be able to set it up so a small family can eat fresh greens. If you want continual growth from new plants, then you're going to require some supplemental lighting designed for that crop (tables for light levels in greenhouses are in most ag libraries)

If you're talking about tomatoes or peppers - then you're going to require both supplemental lighting and supplemental heat.

A MA winter will be too cold to run without heat for heat-loving plants and too dark/short day length. Solar greenhouses (even my 1500 square foot one) are just not energy self-sufficient to run at growing temperatures of low 60's F without supplemental heat. They'll run (with a lot of work and care) at maintenance temps for cold-weather crops 33-40F in most years but don't bet money on it through a January freeze. :-) And maintaining a crop isn't the same as growing a crop.

Heat mats - well, the cost of heating a greenhouse is calculated on the cost per dleiverd btu of your energy source. So using electric heat is 100% efficient but the cost per delivered btu is usually higher than other sources of energy. (delivered btu - how many btu's you actually get to the greenhouse) You'll have to run the numbers to see if a furnace (gas) running at 95% efficiency is more cost-effective than an electric system is 100% efficiency. Do not confuse efficiency with cost per delivered btu.

Frankly, the cost of installing and running both heat and light in small greenhouses is cost-prohibitive unless this is a hobby and nobody cares about the cost. You might recover those costs in a greenhouse for a high-value crop such as roses but you won't for a vegetable crop (far cheaper to purchase organic produce).

But in answer to your immediate question, yes - you'll require supplemental lighting if you want to continue actively growing vegetables through a MA winter.

Good luck with it