All containers need thorough washing every so often to make sure they are clean and pest-free—but wood, metal and stone pots may benefit from a little additional care to keep them looking their best.
To prevent rotting, avoid exposing any part of a wooden container to wet soil. Treat wood before use by applying a wood preservative that isn't poisonous to plants, such as linseed oil (Image 1). Repeat this treatment every year in winter, after you have cleaned out the container. Alternatively, protect wooden containers with wood stain that contains preservatives (Image 2). Make sure the wood is clean and dry before applying the stain. Bear in mind the colors of your plants when choosing the paint color, to avoid alarming clashes. Quiet colors are invariably best because they blend with other pastels, and will set off brasher, bolder schemes. Finally, protect the inner surfaces of a container by lining it with plastic, ensuring that there are plenty of drainage holes in the bottom.
Since galvanized steel won’t rust, and stainless steel is unlikely to do so, rust isn’t usually a problem. A metal watering can, left outside for several years, will still be rust-free. But if you need to drill extra drainage holes in a container that break through the protective seal, rust may set in. To prevent this happening, apply an anti-rust treatment around and inside the drilled holes, following the manufacturer’s instructions. In general, try to avoid scratching metal containers, and keep them clean using any general-purpose nonabrasive household cleaner and a soft cloth.
Modern or reproduction stone containers (or statues) often defeat their purpose by looking too clean, too bright, and too new when they’re used to add instant antiquity. The quickest way to age a new stone pot is to promote the growth of algae by either smearing it with a mixture of cow manure and water, or painting it with natural live yogurt. You can also rub on some grass to encourage algae to grow. Some manufacturers of stone pots and ornaments make their own special aging solutions, which are quick and easy to apply.
If terra-cotta pots have been put in storage over winter, before you use them again give them a good scrub in warm water and detergent to get them scrupulously clean, and then hose them down. This helps eliminate the likelihood of pests or diseases affecting new plants. Also, clean the pots at the end of the season before you put them away. Before planting your pots, soak them in a bucket of water. This saturates the porous clay, which then draws less water out of the potting mix. Ornamental pots can be left out all year if they are frost-proof, but note that there is a difference between being frost-proof and frost-resistant: after a couple of winters outside, frost-resistant containers may start flaking and deteriorating. If in doubt, check with the manufacturer.
Like terra-cotta pots, synthetic containers should be cleaned and scrubbed in warm water and detergent before they are stored, and again when they are brought out for use. Stubborn stain scan be removed with a kitchen scourer, but test a small, discreet area first to ensure that this will not scratch the pot. Choose a dark-colored container that won’t show the dirt for permanent plantings that will sit outside all year.
Excerpted from Simple Steps: Containers for Patios
©Dorling Kindersley Limited 2007