Regional Gardening Reports :: National Gardening Association

In the Garden:
New England
May, 2003
Regional Report

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A container like this one, overflowing with flowers and foliage plants, brightens up any doorway.

Container Gardening

Even though I'm fortunate to have plenty of space in my yard for gardens, I always keep half a dozen planters just outside my door. That way, I can enjoy the plants as I come and go, getting my daily dose of flowers even if I'll be spending the rest of my day indoors at work.

As I think about it, I realize I've fallen into some patterns when choosing plants for my doorway plantings. I usually reserve space for new plants that I want to keep an eye on. Last year it was twinspur; the year before, cerinthe. I keep a few containers of herbs, including basil, thyme, and sage, for a quick harvest. I always have at least one huge container of petunias, because they are just so outrageously colorful. In with the petunias I plant vines -- morning glories or thunbergia, for example -- that I train to climb several strands of twine I run up to a nail in the eave. Sometimes I add a few fragrant flowers, such as stocks or heliotrope.

Choosing Pots
Container-grown plants require more frequent watering than those planted right in the garden. This can pose a challenge if you work long hours away from home. The smaller the container, the more quickly it will dry out. Scanning gardening magazines, I see lots of cool displays with all sorts of clever containers -- such as old boots or cute little wooden crates lined with moss. They look nice, but they're just not practical if you can't be home to water them every few hours.

That said, the most important factor in choosing containers is drainage, because saturated soil will lead to root rot. Containers should have one or more drainage holes. If the holes are in the bottom, you'll need to prop the container up on something so the water can drain freely.

Let's look at the pros and cons of a few popular types of containers.

Pottery. Clay pots are heavy -- a good thing, because plants won't topple in the wind; a bad thing if you have to lug them around. Unglazed terra cotta pots are porous, so plant roots can breathe. They acquire character and beauty with age, and they mix and match well. However, small pots can dry out quickly, meaning you may need to water daily. Glazed pots aren't porous, so they don't dry out as fast. They are available in various colors, and glazed saucers protect surfaces.

Wood. Half whiskey barrels and similar wooden tubs are attractive and reasonably durable. Real whiskey barrels are relatively watertight, so you'll want to prop them up on bricks or blocks of wood (before planting - they're heavy!) so water can drain freely. Other wooden planters tend to dry out quickly, so choose large ones.

Plastic. Plastic is lightweight, so it's easier to work with, and it's waterproof so plants don't dry out as fast as they do in terra cotta. You can find plastic that looks like pottery and other natural materials. However, they don't age and weather like the natural materials. This may be a benefit or a drawback, depending on your aesthetics.

Self-Watering Planters. Self-watering planters have reservoirs for storing water and some sort of system, such as a wick, for delivering water to the plants. They can prolong the time between waterings, but you'll still need to check the reservoirs frequently!

Because plant roots are confined in containers and can't spread in search of what they need, you'll want to give them the best possible conditions. Don't use straight garden soil in your container unless it's exceptionally light and rich. Garden soil tends to be heavy and have relatively poor drainage, and it may harbor disease organisms. In general, it's best to use purchased potting soil, or a mix of soil and compost.

Selecting Plants
Almost any vegetable or annual flower will thrive in a container. If you plant more than one type in a container, choose plants that have similar cultural requirements -- sun vs. shade, moist soil vs. drier -- and appropriately sized pots. Other than that, anything goes!

It's common to combine tall, bushy, plants with those that trail over the sides of the pot. For example, surround a tall, ornamental grass plant with geraniums or pentas, then plant trailing verbena or dichondra vines around the rim. Or surround lacy-leaved dusty miller plants with sherbet-colored portulaca flowers. But you also can't go wrong with a planter full of petunias for sun, or impatiens for shade.

Set plants at the same height as they were in their original container -- don't bury the stem. (The only exception to this is tomato plants, because they'll form roots along buried stems.) You can space plants more closely in containers than you would in the garden -- but remember that they'll need extra TLC. A thin layer of bark mulch on the surface will help hold in moisture.

Most important is keeping soil evenly moist. Water thoroughly, then allow the excess water to drain away. I leave a hose just outside my doorway so I can water plants before I leave for work. Then, if the day is going to be especially hot and sunny, I'll scoot the smaller containers into the shade of the larger ones.

Fertilize weekly with a seaweed/fish emulsion to provide the extra nutrients container-grown plants need. (You can also apply this as a foliar spray.)

Pinch off spent annual flowers to prolong bloom. Be sure to pinch off the entire flower, including the little seed head that forms within or behind the flower. Occasionally prune long stems almost back to the base -- you'll get new growth from there, keeping plants bushy.

Once the season is over, remove plants and soil from pottery containers. If allowed to freeze, the soil may expand and crack the pot.

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