Building a raised box for a banana plant...
 

Last winter I overwintered an in-ground dwarf Brasilian by making a frost cloth tent around it (supplemented with large moving blankets on the really cold nights...26.5F was the coldest). In the late spring it looked alive but showed no signs of growth even with warmer weather. I later discovered half of the corm was rotted away underground, and I'm assuming this was from the winter rains...even though I covered the ground with plastic from the plant out for about 1.5 feet.

The only solution I can think of is to devise a way to keep the ground dry all winter, and I'm thinking of building a raised box(basically just 4 walls, no bottom) and planting a banana so it's 1-2 feet above the ground, in well draining soil that I can also keep covered with plastic. What I don't know is how wide/large this box should be. That's because I don't know much about the banana roots, how far they need to roam, and how deep they need to go.

The only success I've had with bananas has been growing them in the 2 cu ft plastic bags that potting soil comes in. I've overwintered them in these bags and they seem to do very well. The dwarf brasilian I mentioned above, was grown for one or two winters in a plastic bag and had some nice healthy roots circling around the inside of the bag (which was filled with good potting soil). It was easy to control the amount of water in the plastic bag/potting soil...I hardly watered it during the winters although it had a stalk and some leaves. So next time I plant one in the ground, I think the key will be controlling the soil moisture during the cold months.

Any suggestions about the size of this above ground box?

John

Re: Building a raised box for a banana plant...
 

Well draining soil is a good idea, but I would not keep it dry. Last year Tony (sunfish) helped me build a raised planter for my bananas. It is 4 feet across, 30 foot long, and 18 inches high. The 'naners love it.

Re: Building a raised box for a banana plant...
 

That sounds nice, wish I had 30 feet of space! Do you think the banana roots get down below the 18 inch depth? I'm going to have to have individual boxes, so 4x4ft sounds about right. Could you tell me what kind of soil (mix?) you used in the box, and also how cold you get during the winter.

John

Re: Building a raised box for a banana plant...
 

Re: Building a raised box for a banana plant...
 

If 4x4 ft is the interior dimensions it could work.

I excavated about 8 inches below the surface and then installed a french drain down the middle below that.

Soil Mix: http://www.plantsthatproduce.com/col...10_08_Soil.htm

There is about 4 inches of 1-inch diameter mulch on top of the soil.

Annual Temperatures: Weather Station History : Weather Underground

Re: Building a raised box for a banana plant...
 

I would have suggested a minimum of 6 feet square. They will probably not have roots deeper that 18-24" so will not likely have much, if any, roots in the surrounding soil outside the raised bed. Bananas should not be completely dry in the winter: moist, but not soggy, and not dry.

Re: Building a raised box for a banana plant...
 

I probably won't have more than 4 square feet since I'm planting on a hillside. And I see that my winter temperatures are about 10 degrees F lower than the San Diego area ones (usually 3 nights each year down to 28 degrees F). Given the colder weather, do you still think the soil should be kept moist during the cold months.

Re: Building a raised box for a banana plant...
 

There has to be some level of soil moisture. Otherwise you might as well dig them up and store them under the house like make cold climate growers do. You might want to mulch heavily to keep soil/roots from freezing on those coldest nights. Maybe make you raised bed longer (across the hill) and narrower (down the slope) - 4x8 so you have more root area. You also have to remember that bananas do not stay in one place like an apple tree (for example). The pups will come up around the existing plant, so over time there will be some drift in location, so you need to account for that in you thinking about soil/raised-bed area/shape.

Re: Building a raised box for a banana plant...
 

I've finished the box, and looking at it from a banana's perspective it doesn't look that big, especially if the bananas to survive and grow for a few years. It's a good idea to make the box longer across the hill, if I make another box I'll try to do that. But this will have to do for now, it is after all an experiment to find a way to get one plant to survive the winter here without the roots rotting.

For the cold nights I'll build a tent(frost cloth and heavy moving blankets) around and over the box...do you think that'll keep the ground warm enough? Last year it was enough to keep a dwarf Brasilian alive (one night was 26.5F), until the corm rotted in the spring. I wasn't too worried about the ground temperature(I assumed that if the trunk of the plant was protected, the roots would also be). And now I think the 2" thick sides of the box should keep the cold from penetrating from the sides.