Building your own large outdoor planter is a practical weekend project that saves money and lets you match the size, material, and style your patio actually needs.
A store-bought planter big enough for a small tree or a row of shrubs can cost several hundred dollars, and it still might not have the depth or drainage your plants require. Building your own solves that — you choose the material, dial in the exact dimensions, and keep the project under budget. Whether you’re outfitting a deck, a balcony, or a rental patio, the key is matching the planter’s size, weight, and drainage to what you’re growing and where it’s sitting.
What Size Should Your DIY Planter Be?
The depth of your planter determines what can thrive in it. Shallow-rooted plants like lettuce, herbs, and most annual flowers need 12–16 inches of soil depth. Medium-rooted plants such as tomatoes, peppers, and small shrubs need 16–20 inches. Deep-rooted plants — citrus trees, figs, and small ornamental trees — require at least 22 inches of depth with the container several inches wider than the root ball.
For a statement planter that actually makes an impact, aim for roughly 80 centimeters wide by 35–45 centimeters deep. Large trough-style planters around 70–100 centimeters wide work well on patios without overwhelming the space. The wider the planter, the more root room your plants get, and the less often you’ll need to water during hot weeks.
Best Materials for Building Outdoor Planters
Each material brings a different trade-off between weight, durability, cost, and how it handles weather. Cedar and recycled plastic are the go-to choices for wooden planters that resist rot. Fiberglass and fiberclay offer a stone-like look at a fraction of the weight — UV-stabilized fiberglass is especially good for long-term low-intervention use on decks or rental patios where you don’t want to repaint or seal every season. Concrete planters are the heaviest option, which makes them stable but nearly impossible to move once filled.
For the best blend of weight and durability in a DIY build, consider fiberglass or fiberclay. Fiberclay is frost-resistant, lighter than real stone, and can be painted to match your outdoor furniture. If you need something that can handle a hard freeze without cracking, stick with fiberglass or recycled plastic.
Drainage: The Most Common Mistake and How to Fix It
Inadequate drainage is the single fastest way to kill plants in a large planter. Water that sits in the bottom creates a bathtub effect that rots roots. Instead of drilling holes flush with the bottom, drill at least three ¾-inch-diameter holes about 1 inch above the base. This leaves a small reservoir gap that keeps the lowest layer of soil from becoming waterlogged.
Add a minimum 2-inch air gap at the bottom using gravel, clay pebbles, or a plastic drainage grid, then cover it with landscape fabric so the soil doesn’t wash into the gap over time. If your planter sits on a deck or balcony, place a shallow drip tray underneath to catch runoff and protect the surface below.
Weight, Mobility, and Safety for Decks and Balconies
A filled planter is heavier than most people expect. On a deck or balcony, check the structural limit before placing anything that large. If the limit isn’t posted, assume no more than 100 pounds per square foot and calculate the total weight of the planter, saturated soil, and plant together.
If you need to move the planter seasonally — to protect plants from frost or to rearrange the patio — use locking casters rated for at least twice the loaded weight. For permanent planters, skip the wheels entirely; vibration from rolling can stress roots and loosen the soil over time. In hard-freeze climates, move frost-sensitive planters indoors or insulate them with breathable covers and a thick layer of mulch. Inspect for cracks or corrosion every spring and refresh the potting mix every few years since compacted soil loses the aeration and nutrients plants need.
If you’d rather buy than build, our roundup of tested options can save you time: best large outdoor square planters covers durable choices that skip the carpentry.
FAQs
How many drainage holes does a large planter need?
At least three ¾-inch-diameter holes, each placed about an inch above the base rather than at the bottom edge. This prevents a saturated layer of soil at the very bottom that can rot roots, and it allows excess water to drain freely.
Can I leave a fiberglass planter outside in winter?
UV-stabilized fiberglass handles freeze-thaw cycles well and is one of the best materials for year-round outdoor use. Fiberclay and recycled plastic also resist frost damage. Concrete and unglazed ceramic are more likely to crack in hard freezes unless they are sealed or moved indoors.
What’s the best wood for a DIY outdoor planter?
Cedar and redwood are naturally rot-resistant and hold up well without chemical treatments. Recycled plastic lumber won’t rot at all but costs more and can get hot in direct sun. Pressure-treated pine is cheaper but should be lined with plastic sheeting to keep chemicals away from the soil.
References & Sources
- ConsumerSearch. “Large Outdoor Planters: Choosing Durable Styles for Your Patio.” Provides sizing, material, drainage, and weight guidance for large outdoor planters.