Here are some tips for picking the right container for container gardening, courtesy Laura Justice, herbaceous plant manager with the landscape division of the Chalet in Wilmette, Ill.:
1. Bigger is better. Small pots may be cute, but they don’t hold enough soil to support most plants, and the scant soil they do hold dries out so quickly that frequent watering becomes a chore. As a rule of thumb, don’t bother with a container that holds less than 3 gallons (imagine three milk jugs fitting inside). A larger container also will “enable you to do a better display,” Justice says.
2. The right material. Chicago winters, with their unpredictable precipitation and wild temperature swings, are death to many pots. “Nothing is forever,” Justice says. “Even concrete will crack eventually.” The most fragile materials are terra cotta (it absorbs water, which freezes to ice, expands and cracks the pot) and glazed ceramics (even if labeled “frost-resistant”).
So if you just love those materials, keep the pots few and light enough to move indoors to the garage or basement over the winter. Metal and concrete containers fare best if they are emptied (so wet soil can’t freeze and expand inside). Don’t use metal pots on valuable surfaces, such as expensive stone patios or wooden decks, because they often rust and stain, Justice says. For a container to use all year — for winter displays of greens as well as summer planting or as a very large, sculptural accent in the garden — look for good-quality plastics and fiberglass, which are a bit flexible. But over time, hot sun and other weathering can make even those materials fade or crack.
3. Drainage is essential. Unless you are using it for a water garden, the pot must have a hole in the bottom so excess water can escape. Trapped water rots plant roots. No hole? Drill one (use a masonry bit for concrete or ceramics). To let water drain out, Justice suggests elevating any pot on pot feet (buy fancy ones at garden centers, or use three bottle caps or other same-size found objects). Wire baskets with moss or coir liners drain quickly and look lovely but dry out in a trice. Put your plants in a plastic pot (with holes), and hide the plastic pot inside your moss or coir liner.
4. Style matters. Choose pots that are appropriate to the architecture of the house and design of the garden, Justice says. A fancy iron urn might work well for a traditional house with wrought-iron railings, but would look out of place with a mid-century ranch. “A rough cedar box is not for a very formal house,” Justice says. One striking contemporary pot might be an interesting focal point in a formal garden, but don’t clutter a garden with a mishmash of styles. It’s better to invest in a few good-quality planters that are handsome even when empty than to cram your garden with cheap, unattractive containers that detract from the plants.
5. Perspective and scale. When selecting a window box or hanging planter, think about how it will look from below. A pot for a spot across the yard needs to be large enough to make an impact from a distance. Containers to flank a front entrance should be in scale with the doorway and facade of the house.