A cedar planter needs a clear route for excess water to leave the growing compartment. A liner should not block that route, and a layer of gravel beneath potting mix cannot replace a functioning drainage outlet. Decide whether you will plant directly into the box or place separate pots inside it before you choose a liner or fill the planter.
The useful question is not simply “Does cedar need a liner?” It is “Where will water go in this particular setup?” A fabric liner, a waterproof sheet and a removable nursery pot do different jobs.
Choose your planting arrangement first
Direct planting into the cedar box
Here, the planter holds the growing medium itself. Confirm the base design and drainage openings for the exact model, and check whether the supplied liner, if any, is designed to let water pass. Do not assume every wooden planter is built the same way or includes the same accessories.
If you plan to add a liner yourself, ask the planter maker which material and installation method suits the construction. A sheet that turns the box into a sealed reservoir changes how it drains. Do not cover drainage openings or drill into structural supports without checking first.
Separate pots inside a decorative cedar planter
This can make seasonal displays easier to change and allows pots to be removed. But both layers matter: the inner pot needs drainage, and water must not remain trapped around its base in the outer box. University of Illinois Extension's container drainage guidance explains double potting and warns against leaving the inner container standing in accumulated water.
Before ordering, measure the widest part of each pot, including its rim and any saucer. Leave the clearance needed for your planned removal method. Use our inside-versus-outside measuring checklist to record the pot size, clear opening and maximum outside footprint separately. Send those dimensions with your custom planter request.
What a liner does, and what it cannot promise
- A permeable fabric liner can help contain growing medium, but “fabric” alone does not tell you its flow characteristics or suitability for your planter.
- A waterproof liner contains water unless an outlet is designed into it. It should not be treated as a drainage solution by itself.
- A separate pot or insert separates the planting container from the wooden surround, but still needs a practical way to drain and be checked.
Ask what the liner is intended to do, whether it is included and how it should be maintained. A liner is not a guarantee that the wood stays dry, the balcony stays dry or the planter lasts a particular number of years.
Should you put gravel under the potting mix?
Do not rely on a gravel layer to solve a blocked outlet, a sealed liner or standing water around an inner pot. Those problems need a clear exit for water. Gravel also occupies space that could otherwise hold growing medium and adds weight to the filled planter.
The broader claim that gravel always makes container drainage worse is too simple. UC Master Gardeners guidance warns that a coarse layer below finer growing medium can raise the saturated zone. However, a 2025 peer-reviewed study by Avery Rowe in PLOS ONE found that the tested drainage layers usually reduced or did not change overall water retention. Results depended on the growing medium, layer material and depth. The experiment used small plastic containers and measured retained water; it did not test plant growth or full-sized cedar planters.
For a cedar planter, start with the specified base and liner arrangement, suitable container mix and an unobstructed outlet. A gravel layer is not a universal requirement or a cure for overwatering. If you are considering a layered system, get advice for that particular mix, container and crop rather than copying a fixed recipe.
Putting growing medium above gravel is also different from supporting a separate inner pot. In a double-pot arrangement, keep the inner pot above any collected water and make sure the outer container can be checked and emptied safely.
Do not transfer instructions for a special rainwater planter or a designed self-watering reservoir to an ordinary cedar box. Those are different systems.
Inspect the setup before adding all the soil
- Check the empty planter. Identify the base, openings and any liner. Confirm there is a route for drainage rather than assuming one from a product photograph.
- Check the surface underneath. Make sure the planned position does not seal the outlet against the ground or leave water with nowhere to go.
- Check accessories together. A tray, mat, insert or added liner can change the water path. Confirm compatibility instead of adding them one at a time without a plan.
- Confirm usable depth. Do not estimate soil space from the overall height, especially on an elevated planter.
- Choose growing medium for containers. Follow guidance appropriate to the plants and container rather than treating a boxed growing space like open garden ground.
For crop selection and coastal planting considerations, see what to grow in a planter in coastal BC. For soil-volume calculations, use the internal measurements described in our raised garden bed sizing guide.
For patios and balconies, drainage is only half the question
Water leaving a planter still has to go somewhere. Discuss the receiving surface, nearby doors and where runoff may travel before settling on a position. Do not assume a drip tray prevents pooling, and do not cover building drains.
If your building requires a particular surface-protection arrangement, confirm it before ordering. A planter's dimensions do not establish that a balcony or raised deck can carry its loaded weight. The planter, wet growing medium, plants and accessories all contribute.
Our Vancouver balcony planter guide covers the wider access and placement questions. This article does not certify an installation as waterproof or suitable for a particular structure.
If your planter already holds water
Check for a blocked outlet, a liner covering the opening, a saucer that has not been emptied, or an inner pot sitting in accumulated water. If the growing medium remains persistently wet even when the outlet is clear, seek plant-specific guidance about the mix and watering rather than adding more gravel.
Avoid trying to move a heavy, filled planter to inspect its underside. Ask for help with a safe inspection and contact the maker before altering the base or supports.
Wet-weather checks for fall and winter
During wet spells, check how the planter drains rather than continuing a summer watering routine. The RHS container-growing guide identifies winter waterlogging as a particular risk for container plants. A clear outlet and a suitable growing medium remain important even when you are not watering.
- Look for trapped water after rain. Check accessible outlets, saucers and the space around removable inner pots. Clear visible loose debris only where it is safe to reach; do not tip or lift a filled cedar planter to get underneath it.
- Keep drainage and surface protection compatible. If a tray or mat is required on your balcony, agree a way to empty and inspect it without allowing runoff onto neighbouring areas. Do not remove required building protection simply to improve drainage.
- Check moisture before adding water. Rain does not always wet the growing medium sufficiently, and sheltered containers can stay dry. The RHS watering guide recommends checking each container and notes that evergreen plants may still need water during dry winter spells.
If drainage stays slow after an accessible blockage is cleared, review the growing medium as well as the outlet; the RHS maintenance guide identifies both as possible causes. Ask us before changing the planter's base or adding supports: a safe support arrangement depends on the actual construction and filled load, not a generic pot-feet tip.
Seasonal guidance reviewed October 29, 2026. Plant care and the planter's construction need to be considered together; this is not a guarantee against water damage.
Questions to ask before buying
- How does this model drain?
- Is a liner included, and what is it designed to do?
- Is the planter intended for direct planting, separate pots or either arrangement?
- What are the clear internal dimensions and usable depth?
- What placement and surface-protection details need to be agreed?
Compare Coastline Cedar planters, or request a custom size with a photo of the location and a description of how you want to plant. Ask us to confirm the base, liner and drainage details for your selected configuration before ordering. Custom build timing and delivery arrangements are confirmed with the quote.