Tricking vegetables into thinking it's spring

For those of you who are doing greenhouse gardening 12 months a year, will seeds sprout and grow any month of the year if the proper lighting/temperature/ humidity conditions are met?  What kinds of words would I use to research this topic?

Yes, if you provide the proper elements, you can grow anything year-round in your greenhouse. Look for topics like 'year round greenhouse', 'winter greenhouse', etc.

Is it possible to also get fruit trees to fruit out of season as well?

Fruiting is probably difficult with many fruiting trees and shrubs because many of them fruit reacting to day length, and may also need very long days of good sunlight to ripen delicious fruit with plenty of natural sugars. But it is sometimes possible to get fruit a month or two earlier or later by tweaking this and that or with certain varieties.

I grow vegetables and flowers in my attached solar greenhouse all winter. While there's ice skating outside, I've got leafy greens, carrots, herbs and hardy flowers going like blazes inside. But I'm only at 34N so my winter days aren't too short.

Tom Connolly wrote:Is it possible to also get fruit trees to fruit out of season as well?

If you control the temperature and amount of light then sure (though the type of light and the length of the lighting period/temp may come into play). Thing is the cost and space requirements for medium to large plants, much less trees, would be prohibitive in most cases since it may require huge structures and involve very expensive lights/heaters that result in exorbitant power bills (expect a visit from the Drug Enforcement Agency). Plus for indoor crops, pollination would be another challenge (most flowers need to be pollinated in order to produce fruit) though theoretically that could be done manually as well.

However starting seedlings indoors during the dead of winter is very very common and easy to do since the lighting/heat requirements are modest.