The update on the sub-irrigated rain gutter garden is at about the 2-minute mark. Nikki Counts tells us that temperatures have gone as high as 106 degrees. Think about maintaining a garden like this without sub-irrigation. It is a testimony to her sub-irrigated rain gutter system that the plants are doing so well.
If you are new to sub-irrigation, know that the key to success with sub-irrigation is the water & oxygen reservoir system under the plants. The unique aspect of the rain gutter system is the fact that the reservoir is external to the planters rather then internal and provides auto-irrigation to all of the planters.
This is a very creative idea from Larry Hall in Minnesota. It is a major contribution to the field of sub-irrigated planter systems and has stimulated other gardeners to create variations of the system. You can see the evidence of this on the rain gutter garden Facebook group.