Q.Filling A Tall Outdoors Raised Planter
Hi, I have built five square raised planters using new softwood railway sleepers. The planters are 60cm deep and open at the bottom, sitting on normal garden soil/mud underneath. We are looking to plant an ornamental tree in the middle of each one (maybe an olive – nice sunny garden?) with some grasses/flowers around the sides. My question is… can i fill the bottom of the beds with something other than soil to save money/aid drainage? and if so, what should i use and how deep would the soil on top need to be? Thank you

Certified GKH Gardening Expert
There is quite a bit of information to cover, here. These articles will help you to iron out those details:
https://www.gardeningknowhow.com/garden-how-to/info/are-railroad-ties-safe.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/best-soil-raised-garden-beds.htm
https://www.gardeningknowhow.com/edible/vegetables/vgen/raised-vegetable-gardens.htm
https://www.gardeningknowhow.com/edible/vegetables/vgen/raised-bed-soil-depth.htm