Many plants used in containers do not need a very deep bed of soil. In fact, if there is too much soil the roots may spread too far and the soil may not drain properly. Some annuals may only need 6” to 8” of soil. Additionally, less soil will mean less water and a lighter container, making it easier to move (for example, into or out of sunlight) and maintain. If you are starting from scratch it may be a good idea to check with your nursery and assess how much soil your plants will need as they grow larger.
If you’ve found yourself with a very tall container yet only need a foot of soil depth, here are some good options for raising the bottom of the container while maintaining good drainage.
1. Ups A Daisy: These plastic discs, with plenty of holes for drainage, are designed to raise the bottom of your container. Discs are offered in sizes 10” ($4.99) – 18” ($12.99) in diameter.
2. Packing Pearls: Packing pearls are large light-weight balls made from Expanded Polystyrene (EPS), made from 35% recycled materials. This is a great plant insert for odd shaped or wide containers. A drain shield and pot liner can be purchased with the packing pearls or ordered separately. A complete starter kit is available for $19.99.
3. UltraGrow Planter Insert: Fits planters 8” – 14” in diameter and is $12.95.
4. Empty Plastic Pots: This is probably the easiest and cheapest container insert. Just use the empty plastic pots that your plants came in and turn them upside down. This method would work well for small planters. Be sure that there are enough holes for drainage and that the plastic container is sturdy enough to hold the weight of the soil and plants.
For some great tips on container plants (and especially for those with small balcony gardens) check out this blog Life On The Balcony.