They simply lined the colander with a piece of burlap and then put in dirt and plants.
The area that holds the plant was fashioned out of chicken wire and lined with moss to keep the soil in place.
On a side note, Hubers Produce Farm is located on 7110 Mount Vista Rd. in Kingsville, MD. It is a great place to visit and they have done a great job of refurbishing an old barn into a great produce and flower stand.