I have also reached a point where I am just going to have to break down and build one. I am reluctant because I have worked in them for most of my adult life. Here is what I know:

1. No matter how big you build it, it will never be big enough.

2. Over heating on a sunny day is a bigger problem then freezing during the winter. (a lot of tropicals can take it down to around freezing)

3. Any environment perfect for growing plants is also perfect for growing plant diseases. That is why people that have greenhouses for many years have to spend money and time spraying chemicals during part of the year. Going organic is easy the first couple of years but once you catch some sort of disease it is next to impossible to get rid of it completely. You have to be very careful about what you bring in to the greenhouse. The big guys with deep pockets haven't figured out a way to keep their greenhouses disease free so don't expect it to be easy.

When I build mine I plan on making at least part of it removable, that way during the warm season I can open it up and let Mother Nature take care of the pests.

John - I was hoping that you would respond. I have those same concerns about the summer and pests/disease. My shade house system is working pretty good (just too small) and my thought process is to expand that and make a part of it more protected during the winter. I also have a screened in porch and thinking about maybe a collaspable greenhouse on there for those cold months - ahhhhh decisions ......

Lynne

Don't forget how much you have to water plants inside a greenhouse. Another reason I would like to remove sections of the roofing to allow rain to handle that job for me.

For years I have built a temporary greenhouse out of pvc pipe or lumber and just covered it with plastic sheeting or greenhouse plastic. I got amazing results and never had huge problems keeping it warm in the winter.

The problem with those successful years is that now my baby tropical fruit trees are way too big. This year, most of them will go into the largest sized pots I can find (I'm guessing 25 gallons) and that is it - hard pruning from here on out. Having a permanent place to keep them will help my aging back, instead of rolling them in and out with a dolly.

Most commercial greenhouses use a lot of fiber in their potting mix which keeps tender plants from getting water logged - but it also means you have to water things more than once each day, sometimes 4 times a day. I imagine that if you are just trying to maintain a collection of large potted plants you could use a less free draining media and reduce the times per day (but probably still need to water every day at least once). The problems are when you try to use your greenhouse to grow a bunch of seedlings to be planted out in the yard. Then you pretty much have to do things the commercial way if you want every seed to sprout and thrive. That means airy fibery media and lots of hand watering, which means no vacations during the growing season.

We just finished building my greenhouse last fall so I don't have lots of experience with it yet, but thus far it's been a dream come true. I waited for it a long time and the longer I waited the bigger it got in my dream, so hopefully I won't be outgrowing it any time soon.

I'll be using it year round so I put in a cooling system that includes two large fans in one end wall and an evaporative cooling pad and a smaller wall vent in the opposite end. The system has handled our hot weather this year quite well. I also took advantage of my wooded lot and positioned the greenhouse where deciduous trees provide shade in summer. I heated to ~50 degrees last winter, since I grow a lot of tropicals, but I let many plants enter dormancy. I think I watered the actively growing plants about 2-3 times a week, but that was probably not more than half the total plant population, since many things need a dry dormancy. Those only got watered once a week or once a month, depending on whether or not any top growth remained. I've been watering more since it got warm, and all the air movement from the fans dries things out faster. Still, I went 3 days over Memorial Day weekend without any losses, and I have a friend I can depend on for longer trips.

As for pests, things may change down the road, but Mother Nature has moved into the greenhouse already to provide some control measures. I was pretty careful when I brought my plants in last fall but still grew a robust crop of aphids by late winter. I sprayed insecticidal soap several times a week and finally even defoliated the brugmansias, but this spring the daddylonglegs/harvestmen moved in and now I have a veritable army on patrol and no more aphid problem. There are also skinks and toads taking care of the slugs. I'm sure there will be more pest adventures down the road but I'm going to enjoy the honeymoon period while I can.

As for pros and cons, pros for me include:
1. I can grow (even) more tropicals
2. No more tropicals in the garage in winter so we can park cars in there
3. No more tropicals in the bathtub in the winter
3. I can grow winter blooming bulbs that require dry summer dormancy
4. I can finally enjoy the winter blooming salvias
5. All my tender plants enter spring happy and healthy rather than tortured and near death from being kept in the garage
6. I have a squirrel free place to start seeds and a more controlled environment for cuttings

Cons are
1. A big investment in plants dependent on electricity to run the fans, heat, and cooling system. I got through winter storms, but still need to install a back up generator.
2. One-size-fits-all winter temps really don't fit all, so now I want a cold frame.

Thanks Karen for the feed-back. I can totally relate to the bathtub deal - my beautiful garden tub holds my tropicals in the winter also - good thing hubby and I are shower people :D Right now we keep the dormat plants in the crawl space under the house and check them on a monthly basis - other plants stay in the house ......

Lynne

My greenhouse is mainly just a big fun hobby to me and I love it. If it never saved me a penny, I would still see it as being worth every penny I paid for it and whatever resources I put into it. There is nothing like going out there during a cold winter day and enjoying the sunshine and warmth and feeling my hands in the dirt. It's a great escape.

Outside of that, I concur with everything else that has been posted. The humidity is a big thing I have found difficult to control which the spider mites love. I have had to result in defoliating brugs as well to control a pest infestation. We are discussing building another one and I am with John, I'd like to have a structure that the top can be taken off of to let nature do its thing. That way I too can have a more permanent place for things that are not hardy without having to drag things in and out of the greenhouse.

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