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Container Gardening: Pots Galore!: Choosing Your Containers

Photo courtesy of Flickr cc/Eric Gross
Photo courtesy of Flickr cc/Eric Gross

You can grow just about anything in a container these days. As you tour The New York Botanical Garden, you will see containers full of tall, elegant bamboo; lush evergreen conifers and diminutive heathers; sassy sedums and graceful grasses; tasty tomatoes; and an endless supply of non-stop annuals and tempting tropicals.

One of the reasons for this surge in container planting is improvements in the products that you can buy, particularly the containers themselves. In the past if you were making a choice based on aesthetic appeal and looking for price-worthy options you would be limited to wood or terracotta. 

Today there are many containers of different synthetic materials that are inexpensive, lightweight and relatively durable. They are also much more attractive than ever before.

Reconstituted stone and concrete tubs are less expensive than real stone (and lighter). These pots are generally made out of reconstructed limestone and weather well. Alpine troughs and jardinières are two examples.

Poly resin or polyethylene pots come in many shapes, sizes and colors. High quality synthetic containers make handsome reproductions of classic containers, ranging from the familiar faux terracotta to washed stone, cast iron, sandstone, stoneware and faux wood.

Look for pots that are treated with UV light inhibitors, which prolong the life of the pot and reduce the chance of fading. A well-made poly resin (synthetic/plastic) container should not fade in the sun.

Pay attention to the construction of the pot. If too thin, it may become brittle when exposed to the elements and crack. In general, these plastic replications tend to be extremely weatherproof and can be left outside in the winter. Since they are lightweight and affordable, it is easy to design large containerscapes (a tableau of assorted containers in various sizes).

Plastic and terracotta containers; photo courtesy of Flickr cc/The Greenery Nursery
Plastic, Ceramic and Terracotta Containers; photo courtesy of Flickr cc/The Greenery Nursery

The only real drawback with plastic containers is that since they are light, they can sometimes blow over in heavy winds. Plastic is also not a good insulator. Because they can heat up in the intense summer sun, the containers should be well watered so that plant roots do not over-heat. In colder climates, the thin material does not provide perennials with the winter protection that they need, so the containers should be wrapped with bubble wrap and burlap. In the New York City area (Zone 6), this generally is not a problem.

With all these new products, it is important not to lose sight of the old stalwarts in the container world. Terracotta is a classic for good reason. The unglazed clay pots blend effortlessly into any garden setting and add instant charm. Clay is porous so that the plant roots are provided with good drainage and air circulation.

Terracotta is nice and thick so it protects plants from sudden temperature changes and does not blow over as easily as plastic in heavy winds. It also provides good support for top-heavy plants. Some pots are advertised as being “frost proof.” In general it is not a good idea to leave these pots outdoors in the winter. Soil expands and contracts, and it freezes and thaws. This movement is often enough to crack the container. Its Achilles heel is that is breaks easily.

Wooden barrels and window boxes are always popular. To increase the life of your window box, use a plastic liner that you place inside the window box. Always make sure that you have adequate drainage holes.

When choosing wooden containers, remember to look for wood that has been painted with non-toxic wood preservative and colored wood stain or paint. If you are interested in longevity, choose rot-resistant wood such as cedar and red wood. On the other hand, if you are in the market for a bargain, pine is a good choice but will need wood preservative and three coats of paint.

The wood on any container should be at least 1-inch thick. Wood containers are good insulators; soil retains its moisture in the middle of the summer and does not overheat. It is best to raise wooden tubs off the ground so water does not pool under the container; place bricks underneath to prevent rot and improved drainage.

Galvanized containers such as florists’ buckets are fun for a different twist. Make sure to drill drainage holes in the bottom before you plant. Galvanized containers do not rust, but they do warm up in the summer sun and are best used in partial shade.

If you would like to have fun and get fancy with your pots, try painting terracotta with flat latex paint and plastic with acrylic emulsion. Whatever you do, make sure that your containers have good drainage holes. If not, it is time to get out the electric drill and a masonry bit.

Potting soils today often have fertilizers added and provide excellent drainage. If you are challenged by constant watering, you have several options. Self- watering containers have a small reservoir that you fill with water that is then wicked up into the potting mix. This will dramatically decrease your watering duties. Drip irrigation is another possibility for the container gardener.

If you are a product person, try the water retaining polymers (such as Terra Sorb® and Soil Moist™) that are now for sale. These crystals expand when placed in water. They hold onto the water until the medium around them is dry and then release the moisture. Some people swear by them; others do not. Make sure you follow the direction carefully—these crystal expand exponentially when place in water; too many in a container will cause the potting soil to erupt over the edge. 

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