Walk into any garden center or browse any outdoor furniture retailer and you will find deck planters in two dominant materials: cedar and composite. Both are marketed as durable, weather-resistant, and attractive — but they perform very differently over time and suit different priorities. Cedar is a natural material with a long track record in outdoor woodworking. Composite is an engineered product designed to eliminate the maintenance drawbacks of wood. Neither is universally better; the right choice depends on budget, aesthetic preferences, maintenance tolerance, and how long you expect the planter to last.
This article compares both materials across the factors that matter most for deck planters: durability, weight, cost, maintenance requirements, appearance, environmental impact, and suitability for different plants. If you are still figuring out which style of planter fits your deck layout, start with the deck planter style guide before committing to a material.
Cedar: The Natural Standard
Western red cedar has been used in outdoor construction for over a century. Its natural oils make it resistant to moisture, rot, and insect damage without chemical treatment. It is lightweight relative to its strength, machines cleanly, takes paint and stain well, and weathers to an attractive silver-gray if left unfinished.
Cedar Durability
Western red cedar in outdoor applications typically lasts 10 to 20 years depending on conditions, finishing, and care. In a planter context — where the interior is in constant contact with moist soil — the interior walls degrade faster than the exterior. Lining the interior of a cedar planter with EPDM rubber membrane or heavy-duty plastic sheeting (6-mil poly) dramatically extends the life of the wood by preventing direct soil-to-wood contact. Unlined cedar planters that hold moist soil continuously may show interior rot in as few as 5 to 7 years.
Joinery is the most vulnerable point. Mortise-and-tenon and through-bolt joints that pull apart allow water infiltration. Look for planters with stainless steel hardware, exterior-rated wood glue, and tight-fitting joints. Avoid planters with galvanized hardware — zinc coatings corrode in acidic soil environments.
Cedar Weight
Cedar is one of the lightest construction woods by volume. An empty 24x18x18-inch cedar planter box weighs roughly 25 to 40 pounds depending on wall thickness and joinery style. This is a meaningful advantage for deck load management and for anyone who moves planters seasonally.
Cedar Cost
Cedar planter boxes are moderately priced at retail — typically $40 to $150 for mid-size freestanding units and $20 to $60 for railing boxes. DIY cedar planters can be built for $20 to $60 in materials. Cedar lumber is widely available at home centers, though prices have been volatile in recent years. Clear, knot-free cedar commands a premium; construction-grade cedar with tight knots is less expensive and still serviceable for planters.
Cedar Maintenance
Cedar left unfinished weathers to silver-gray and holds up reasonably well outdoors, but it benefits from periodic treatment. Applying an exterior wood oil or deck stain every 1 to 3 years slows weathering, maintains color, and reduces checking (surface cracking). Teak oil, linseed oil, and penetrating wood sealers all work. Avoid film-forming finishes like polyurethane on outdoor planters — they trap moisture and peel in freeze-thaw climates.
The interior of the planter should be inspected annually. If the wood shows soft spots, discoloration, or fungal growth, that area should be cleaned, dried, and treated with a wood preservative before the next planting season.
Composite: The Low-Maintenance Alternative
Composite lumber — a blend of wood fiber and recycled plastic resin — was originally developed for decking and has expanded into furniture, railings, and planters. It resists rot, insects, and moisture absorption far better than natural wood. It does not check, split, or splinter. And unlike wood, it requires virtually no annual maintenance.
Composite Durability
Quality composite planters are built to last 25 to 30 years or more under normal outdoor conditions. Unlike cedar, composite does not rot from the inside out when in contact with moist soil. This makes composite particularly well-suited for planters that will remain filled and in place year-round. Most premium composite brands (Trex, TimberTech, AZEK) carry 25- to 30-year warranties on their decking products; planter products typically have shorter warranties but still significantly outlast wood.
Composite is not immune to all degradation. Low-quality composite with high wood fiber content can absorb water and develop mold on the surface. Capped composite (where a protective polymer shell encases the wood fiber core) resists this far better. When buying composite planters, look for "capped composite" or "fully capped" construction.
Composite Weight
Composite is heavier than cedar — roughly 1.5 to 2 times the weight per board foot. An empty composite planter the same size as a cedar equivalent will weigh 40 to 75 pounds. For large freestanding planters that will not be moved, this is not a major issue. For railing planters or applications where seasonal relocation is desired, the weight difference is meaningful. Verify deck load capacity before placing multiple large composite planters.
Composite Cost
Composite planters carry a significant price premium — typically 2 to 4 times the cost of comparable cedar products. A mid-size freestanding composite planter retails for $150 to $400. Railing planters in composite are $60 to $120 each. The higher upfront cost is offset by lower lifetime maintenance cost and longer service life. Over a 20-year horizon, a composite planter often costs less than the combined cost of a cedar planter plus refinishing materials and eventual replacement.
Composite Maintenance
Annual maintenance for composite planters is minimal: rinse with water, scrub with a soft brush if mold or algae develops, and inspect hardware. No staining, oiling, or sealing is required. This makes composite the better choice for homeowners who want plants without a maintenance burden.
Appearance: Natural vs. Engineered
Cedar has genuine wood grain, natural variation in color, and a warmth that engineered products do not fully replicate. Freshly finished cedar has a rich, honey-gold tone that weathers gracefully. For gardeners who value natural aesthetics, cedar is hard to beat.
Composite has improved considerably in appearance, with realistic wood grain embossing and a range of colors from warm tans to cool grays. However, it looks more uniform than real wood, and some homeowners find it reads as obviously synthetic. The aesthetic gap is narrowing but has not fully closed.
Environmental Impact
Cedar is a renewable resource when sourced from certified forests (look for FSC certification). It is biodegradable at end of life. The concern is that western red cedar in old-growth forests is a limited resource; much commercial cedar lumber comes from plantation-grown trees that grow faster but are less dense.
Composite is made partly from recycled plastic and wood waste, diverting material from landfills. However, composite is not biodegradable, and recycling at end of life is limited. The environmental calculus is roughly comparable — neither material is clearly superior across all metrics.
Which Material for Which Application?
- Best for DIY builders: Cedar. Easy to cut, fasten, and finish with standard tools.
- Best for low maintenance: Composite. Essentially maintenance-free once installed.
- Best for railing planters: Cedar (lighter weight). Composite railing planters are heavy.
- Best for large freestanding planters that stay in place: Composite. Better long-term durability for permanently placed, always-filled containers.
- Best for budget-conscious buyers: Cedar. Lower initial cost.
- Best for long-term value: Composite. Lower lifetime cost when maintenance and replacement are factored in.
Other Materials Worth Mentioning
Ipe (Brazilian hardwood) is denser and more durable than cedar — sometimes compared to composite in longevity — but it is expensive, heavy, and sourcing from certified forests is harder to verify. It requires annual oiling to maintain appearance. Teak behaves similarly.
Pressure-treated lumber is inexpensive and very durable, but modern PT wood (ACQ or CA treated) contains copper compounds that can leach into soil in small amounts. Most research suggests levels are too low to affect plant health, but gardeners growing edibles in direct contact with PT lumber may prefer to use cedar or composite for the soil-contact portions. The soil amendments guide has information on soil health that is relevant to any container growing situation.
Frequently Asked Questions
Does composite get too hot in direct sun for plants?
Composite surfaces can get very hot in direct summer sun — sometimes reaching 140 to 160°F on the surface. However, the soil mass inside insulates roots from this heat. Plants close to composite walls in full sun may show some edge heat stress; a 1- to 2-inch gap between the soil surface and the planter wall, or a light-colored interior liner, reduces this effect.
Can I build my own composite planter?
Yes, though it requires more effort than cedar. Composite decking boards can be cut and assembled like lumber, but composite does not hold screws as well as wood — use stainless steel composite-specific screws and pre-drill all holes. Composite also cannot be planed or shaped easily, so joinery options are more limited than with wood.
How long does cedar last as a deck planter?
Unlined cedar planters in continuous contact with moist soil typically last 5 to 10 years before interior rot becomes a problem. Cedar planters lined with EPDM or heavy-duty poly, or that are emptied and dried seasonally, can last 15 to 20 years with periodic exterior refinishing.
Is there a significant color difference between cedar and composite?
Fresh cedar has a warm, honey-gold tone that weathers to silver-gray within 1 to 2 seasons if not oiled or stained. Composite comes in fixed colors that are more stable over time — they fade slightly but do not change character the way cedar does. If you want to match existing composite decking, a composite planter is the easier color match.
Which material is better for edible plants?
Both cedar and composite are considered safe for growing edibles. Cedar's natural oils are not harmful to plants at the concentrations present in lumber. Capped composite contains no wood fiber at the soil contact surface. Pressure-treated lumber is the material most often questioned for edible use; for peace of mind, line PT planters with heavy-duty plastic if growing vegetables.