By Glenn Withey

While my partner and I enjoy renovating garden beds, it may take two or three years before a design concept comes to fruition. With container gardening, results come a lot quicker. Gardening in containers allows you to create a totally different look each year, if you choose.

Selecting Containers

Possibly the most important rule is having a quality, aesthetically pleasing container. If an unplanted flowerpot is homely, it will most likely remain homely when planted. Beautiful pots can be expensive, but you can take years to build a nice collection, one piece at a time.

Another consideration: is the ceramic container frost-proof? As a general rule, the higher the pot’s firing temperature, the better are its chances of long-term survival. That said, on occasion a pot may crack if waterlogged and frozen.

Metal containers can be quite nice, but offer no insulating value—roots can burn in the summer, and plants freeze even more quickly in winter. This problem can be alleviated, to a degree, by lining the pot with a firm insulation material. Rust stains from steel containers may also be a problem, so be aware when siting them on a patio or deck. There are some very handsome fiberglass/resin pots around, but we’ve only seen a few good-looking plastic pots.

When it comes to the container’s size, there is another rule of thumb: try to use as large a pot as possible (so long as it looks good). The larger the container is, the slower it will be to dry out.Also, in a windy site, a taller pot with say, a Japanese maple, will have a greater chance of toppling over, versus a short, wide container with the same plant.

Try to group containers together in some odd number. If you have a symmetrical garden layout it’s fine to keep them so but otherwise if you have, say, four pots, think about creating a group of three with the last one offset. Stand-alone containers work, if of good quality. I usually keep pots below the height of railings and windows if they are in front of them, but that’s not a fast rule—every situation needs its own consideration.

Soil

As the saying goes, “Garbage in, garbage out.” This applies to your soil, too. The most expensive brand may not be the best, even less likely will the cheapest. If you have a brand that works well for you, stick with it. When trying a new soil, plant one container and see how the plants perform.

Fertilizing

I used to aggressively feed containers with both time-release and liquid fertilizer. Over the years, I’ve gotten in the habit of using less with good results.

When planting, add a time-release fertilizer and skip the weekly liquid feedings. Come August, or when the planting begins to flag, use some water-soluble fertilizer to pep things up.

Certain plants, such as brugmansia, are food hogs. This plant is difficult to overfeed. I still remember watching one being potted up, and my friend put in a good pound of time-release fertilizer. The plant loved it…

Plants

In my early days I relied on annuals. Nowadays, I use at least half evergreen plants, as they offer year-round interest. If there’s a suitable spot in the ground when I take the planting apart, I will reuse the plants.

Since day one I’ve always included some fragrant plants. I once planted lilies in containers by my entry door. Wonderfully fragrant, they thrilled me. Then they went out of flower and summer wasn’t even half over. By the end of summer I’d learned my lesson. Most floral “show-stopper” plants are not very appealing out of flower. Nowadays I select plants that earn their keep. Good foliage and structure is most important, followed by how long a plant will flower.

When using shrubs or small trees, remember that if you want to remove a plant (intact) at some future date, the opening of the pot needs to be wider than its middle or bottom. This may seem self evident, but often containers flair slightly inward, which results in much swearing when trying to remove said plant.

Root hardiness is critical when selecting permanent plants. Containers freeze solid long before the ground does. As a general rule, if a plant is borderline hardy here in the ground, don’t expect it to thrive long-term in a pot. Of course there are exceptions to this rule, but spending $100 on a conifer is likely a wiser choice than spending the same amount on a phormium.

Nowadays, I love simple, graphic plantings. Three beautifully clipped, dome-shaped boxwoods are often more pleasing to the eye than an eclectic mix of plants. Of course one is entitled to change one’s mind, and I might say the opposite next year.

When I create mixed containers, I generally don’t cram as many plants in as I used to. Twenty years ago, I might’ve smooshed ten different species into one pot. Now, I am much more likely to put in three different species, or even a single kind of plant per pot, with five or seven pots grouped together to create a mixed look.

If you want to mix evergreens with annual color, be careful how you place rambunctious annuals. While boxwood and yew can take considerable shading, many conifers will resent it and dead chunks may appear. Also, planting a four-inch annual amongst the roots of a well-established permanent plant could be tricky work. Unless it is quite tough and vigorous it will need more TLC in order to compete. A container where all the plants are of relatively equal size and the “playing field” is more even will increase the odds of a beautiful outcome.

Watering

Plan on either installing a drip system or being there throughout the summer, hand-watering. At the Dunn Gardens, where I work, I hand water. Summer is the one time of the year when I want to be there, enjoying the best of what the region has to offer.

For a lot of people, drip irrigation is the choice. Be aware that once a system has been installed, it will need maintenance. Emitter lines will plug, so check the system several times a year.

Once a pot has dried out and the soil has pulled away from the edge, it takes diligence to rehydrate it. Repeated soakings are in order, especially with a peat-based mix.

Conversely, keep the container’s drain holes clear. On more than one occasion I’ve had plants almost drown. Roots can grow in or out through the drain holes and plug them.

Train your eye to notice the color of foliage—leaves will often show stress with a slight graying before it’s too late to save the plant, but you need to act fast. The beauty is—if you lose the plants, at least you still have the container to replant!

Grooming

Remember to maintain the plantings weekly. Even supermodels look dreadful if they aren’t cleaned, groomed and kept healthy.  NWGN