Sure, you can start a garden just by digging a hole in the ground, but it can be a lot of fun to go the extra step and build or create outdoor planters for container gardening. A wide variety of household items can be repurposed into garden planters, and if you're handy with a hammer you can even build your own planter box from scratch
Assess your yard and decide where you would like to install a planter. Do you want to build window boxes on every side of your house, or would you like to build a round planter circling your favorite tree? Do you want to build a raised bed for your vegetables, or would you like a funky centerpiece for your front yard?
Consider what kind of plants you want to grow. Small annual flowers like marigolds or impatiens only need a container six or eight inches deep to spread out their roots, while bigger plants like tomatoes or calla lilies will do best in a two- or three-gallon tub. Dwarf trees and shrubs can be grown in containers, although they will need a very large container or will need an open bottom so the roots can access the earth.
Look around your house for items you can reuse as garden planters. Old buckets and pails are an obvious choice, but make sure they never held any solvents or other toxic chemicals that could harm your plants. There are paints specifically formulated to stick to plastic so that you can create your own color scheme and designs, just in case kitty litter jugs don't fit into your garden decor. Coffee cans, sewing baskets, tool boxes or fruit crates can also be made into planters.
Keep an eye open at estate sales, flea markets and thrift stores for deep, enclosed items that can be repurposed into garden planters. Planting flowers in old claw foot bathtubs, rusty wheelbarrows or carved wood dresser drawers can add a touch of whimsy to your garden.
Build a planter from scratch with lumber and nails. A wide variety of wood in a range of colors and finishes can be found at any home improvement store or lumber yard. You could also consider reusing the wood from old shipping pallets or railroad ties to build a planter. Before you purchase your lumber, measure the area where you would like to install your planter and draw up a plan so you have a rough idea how much wood you'll need. Buy a little extra wood, just in case---if the project takes you a month to build and you end up needing more wood, the lumberyard might be out of the particular variety you bought last time.