You generally want a drainage-friendly layer plus good potting mix , not random junk or just gravel, and the planter must have drainage holes for anything you put in the bottom to work well.

Key principle: real drainage vs myths

  • True drainage comes from:
    • A planter with holes so excess water can escape.
    • A loose, airy potting mix that does not compact.
  • A thick solid layer of stones under soil does not magically “pull” water away; water can still sit where soil meets stone and cause root rot if holes are missing or blocked.

Best thing to put in the bottom

For most planters:

  • Check or make drainage holes
    • If there are no holes, drill some appropriate for the pot material (plastic, metal, wood are easy; ceramic needs masonry bits).
  • Add a coarse drainage layer over the holes (optional but helpful)
    • Broken terracotta or pottery “crocks”.
    • Small gravel or pebbles.
    • Small rocks or crushed stone.
      These pieces sit right over the holes to stop soil washing out and to keep holes from clogging while still letting water flow.

Good materials to use

These work well at the very bottom, especially in large containers where you don’t want solid soil all the way down:

  • Broken pots / clay shards / crockery
    • Classic choice to cover holes and create small air pockets.
    • Helps prevent compost loss and clogged holes.
  • Gravel, small pebbles, or small rocks
    • Adds weight and stability.
    • Creates a space where water can collect temporarily before exiting through holes.
  • Perlite or coarse sand mixed into the lower soil
    • Perlite is very light and keeps mix airy and fast-draining.
    • Coarse sand can improve drainage in heavy mixes (avoid very fine sand).
  • Lightweight fillers for very large planters (under a drainage layer)
    • Clean plastic bottles or jugs with lids on.
    • Foam blocks or non‑dissolving packing peanuts.
    • Crushed cans, bundled plastic bags.
      These reduce how much soil you need and keep big planters lighter while still leaving space for water and air.

Simple rule of thumb: a thin layer of coarse material at the bottom + quality potting mix with perlite through the root zone gives better drainage than a thick rock layer and heavy soil.

What to line the bottom with

Liners help keep soil in while water drains:

  • Coffee filters, newspaper, or fabric scraps
    • Sit over the drainage pieces to stop soil falling through.
    • Still allow water to move out.
  • Landscape fabric or burlap
    • Useful for big planters with fillers (rocks, bottles, foam) underneath.
    • Keeps soil separate so it doesn’t sink into the filler layer.
  • Plastic pond liner (for outdoor planters)
    • Used as a liner with holes cut where drainage is needed.
    • Protects decorative containers and guides water to exit holes.

What not to put at the bottom

  • No drainage holes + “drainage layer”
    • A layer of rocks in a pot with no holes just turns the bottom into a hidden reservoir; roots will sit in stagnant water.
  • Dense, heavy garden soil alone
    • Compacts and holds water; poor drainage even with a rock layer.
    • Use container potting mix instead.
  • Biodegradable packing peanuts or corn‑based foam
    • They dissolve and turn mushy, blocking spaces and hurting drainage.

Quick setup recipe

  1. Ensure the pot has drainage holes.
  2. Put a thin layer (1–2 inches for small pots; 2–4 inches for large) of broken pots or gravel over the holes.
  3. Optional for large pots: add lightweight filler above that if you don’t need full depth for roots.
  4. Cover filler with landscape fabric or similar.
  5. Fill the rest with a high‑quality potting mix, optionally with extra perlite for better drainage.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.