I love greenhouses and their potential.

I've always found, though, that smaller "hobby" greenhouses don't live up to their hoop-la. The small size makes it difficult to control temperatures -- too hot in the summer (even with "venting") and too cold in the winter (little heaters heat uneveningly in such small houses).

And, maybe more importantly, the small size doesn't allow for good placement of plants, enough space to actually grow anything in worthwhile quantity, and good traffic flow. They almost always quickly get stuffed with miscellaneous items just for storage. Along with spiderwebs and dust.

With that said, get the biggest one that will fit your site. I've always told my gardening and design students that the minimum for even a "hobby" greenhouse is 14 by 21. That allows for side benches and a middle "work" table/bench.

Use the greenhouse for seed germination (flowers, veggies, specialty plants, etc.). Move transplanted seedlings out to a tall coldframe to actually grow them on and harden them off.

Grow tomato plants in the ground. There are hundreds of cool-season/short-season tomato cultivars that will do well in Sonoma. In a greenhouse, you'd have to grow them in small pots and tomatoes don't really like small pots.

Grow lettuce outside in the winter and hose off those aphids. Lettuce grown in a greenhouse suffers tremendously from the occasional overly-hot winter day (compounded in the greenhouse).

Grow some just-too-tropical plants that need a little winter protection and a little more heat than your summers provide: various orchids, bromeliads, epiphyllum, Eucharis, begonias, plumerias, and so much more.

Joe

Thanks for the advice! I've actually got a pristine spot for a cold frame and have been considering that as a cheaper alternative. Sounds like that might be the way to go. I appreciate your thoughts!

I am in your neighborhood and agree pretty much with Joe. I have a small 9x12 redwood greenhouse. I built hydroponic or hot water heating into the concrete floor which worked well when I could afford the propane to heat the water. I use it primarily for propagation during the winter and it is too hot for summer use without cooling which I also can not afford! I bought a plastic covered carport from Costco, it is 10x20 feet, and instead of using the brown plastic I covered it with 6 mil plastic from Harmony Farm Supply. It has lasted for almost 10 years so far. As I live in the woods my work area is partly shaded so I do not use shade cloth. The cold frame is full much of the time with plants propagated during the winter now being taken out. If you have any further questions feel free to email me. Al

Thanks so much, Al. Yep, I'm thinking the much more inexpensive cold frame is the way for me to go. I can do everything I wanted except attempt at growing those summer tomatoes. Oh, and fantasizing about walking into the lush earth-scented arboretum my greenhouse was going to be. LOL But honestly, I think you both are right. It would have been an expensive toy that probably isn't worth it unless I'm willing to go big and heat it.

Sure would love to see your greenhouse, Al. Could you post a picture?

I live in the SF bay area, and have a small greenhouse made from old windows and french doors (about 8x10). With doors on both ends and 2 large window openings on each side there is barely adequate ventilation in the hot months. A small fan on a thermostat helps some, and the windows have the automatic vent openers - what helps most is shade cloth hung on the OUTSIDE of the roof. I take it down for winter. The greenhouse is next to another small building so there is shade next to it - this helps a a source of cooler air in summer. If I could re-design one thing - I would have made roof vents...

For heating I have a small, plastic-enclosed area inside the greenhouse with a heat mat on each shelf. This has been adequate for keeping sub-tropical cuttings (think Coleus etc.) happy for the winter. It also is a good place to start seeds of heat loving plants. I grow tomatoes "on" in 1-2 gallon pots before putting them out in the garden (last weekend actually).

My plumeria and similar plants do OK in the main greenhouse over winter. I am tempted to make a larger enclosure within the greenhouse just for them, with a heat cable and jugs of water to absorb warmth and release it at night.

Chad