obdiah

well for the last two years I have been working on a way to grow edible bananas in zone 7 in a pit type green house with no supplemental heat after some experimenting I have a rajah puri with a bunch hanging mature enough to harvest the method consists of a 6 ft dia hole 5 to 6 ft deep with a framed octagonal top of 2x4 construction and covered both sides with poly green house covering on both sides ( doubled walled ) the plant is in the ground at the bottom of the pit normal fertilizing methods were used watering needs are almost zero especially in winter the main obstacles were flooding the first year before installing a drain line even though the pits are on a steep hill side in flat land it would be nessary to dig a sump in the botom and to install a sump pump on a hillside a simple draine works great
the coldest temp measured in the covered pit in winter was 44 f with an outside tempature of 8 f the soil temperature of 51 F maintains an above freezing temperature although grouth is slowed in winter they still continue to put out new growth I remove the top after the last frost and they really take off

I experimented with several varites including dwarf cavindish, rajah puri blue java so far rajah puri has worked the best dc dosent like the cooler temps and blue java tends to be too tall I have dug a new pit and am finishing it up now and plan to try dwarf namwah I have also started a new 8 ft x 30 ft trench house along the same lines 6 ft deep I have the trench dug but it may be spring before I complete it and plan to have 8 or 9 plants in it year around not sure of the variety yet but dwarfe types are better suited because of ceiling height limitations there several more pictures in my gallery if your interested
picture below was taken in September this year

subsonicdrone

when you build the trench greenhouse,
will you dig deeper and lay some loops of weeping tile

JustAGuy

Thanks for the update. Let us know how they taste. Please make a post about your trench greenhouse I'm very interested in it.

I just moved to 7b (north georgia) and play to dig a greenhouse 2-3 feet down, have a north wall that is insulated/no glazing, catch rain off the roof into IBC tanks inside greenhouse and then heat the water in tanks with a diy solar water heater drainback system which hopefully would be enough to keep above freezing through winter.

subsonicdrone