Back Issue
May/June 2001

Planting Container Gardens
by Mary Jo Bridge Palmer

One of the many joys of spring is deciding what to plant in all those pots, window boxes and hanging baskets on your patio and in your garden. It’s not hard to create winning combinations. Just keep a few basics in mind and let your imagination soar.

Choose Your Container
You can plant in anything. Just remember that any container used outside must have a drainage hole. I like to plant in my sons’ outgrown shoes. Those holes they wore out in the toes are perfect for drainage, and they look wonderful grouped by the back door. In keeping with the shoe theme, I’ve even seen a collection of women’s shoes (mostly high heels) planted with brightly colored annuals and foliage plants. Your children’s outgrown snow boots would be perfect.
If you have a jumble of old baskets, use them! Line them with a layer of plastic and cut a few drainage holes in the bottom. These baskets won’t last forever, but they will be very attractive and effective containers for one season outdoors.

Prepare Your Container
Any commercial potting soil is fine to use, right out of the package. However, if I’m using a very light mix, such as ProMix which has a lot of peat moss, I like to add topsoil: about one-third topsoil to two-thirds ProMix. This makes the mix heavier and easier to wet after drying out.

Always add a slow release granular fertilizer, such as Osmocote 14-14-14, to the potting mix: about one or two handfuls depending on the size of the pot. A whiskey barrel will need about four or five handfuls. Every time you water, the Osmocote granules will release a little fertilizer into the soil for the plant roots to pick up.

You usually don’t need to put anything in the bottom of the pot for drainage. In shallow planters, it’s better to have the soil available for plant roots; use a bit of window screen rather than pot shards to cover the hole in the bottom of the pot. But if you’re planting a whiskey barrel you can fill the bottom with bark chips up to about one-third. This will save you from having to fill the whole container with potting soil.

Color Combinations
Some folks tell me that they can’t choose the plants themselves because the combinations might not look “perfect.” You’d be surprised how well you can do. For the most part, plants have a happy way of always combining well together. An easy color combination is the three primary colors: red, yellow and blue.

If in doubt, start by choosing plants that bloom in one color that you particularly like, then add an accent color. For example, if you’re a red person, all shades of red will go together but the combination needs an accent, such as blue or white, to give it some zing. Blue and purple flowers need an orange or red accent. Adding white to any combination will always be effective.

You will need to pay attention if you’re combining orange and red blooms. These can be quite unpleasant. But if you add blue your red and orange combo can be very pretty.

Your color combinations may not turn out exactly as you had imagined. They may be better! If you don’t like them, just cut off the offending flowers and enjoy the foliage.

Pick Your Plants
Varied shapes in a container are more pleasing to the eye than a mass of one shape. Consider the plant’s shape: Is it big, skinny, bushy or soft and trailing? An attractive container will combine a variety of flower colors and plant shapes. Foliage is important, too. If one or two of your plants have variegated or interesting foliage, so much the better.

Contrary to popular belief, you don’t need a vertical accent right in the middle. Sure, go ahead and plant that dracaena, but position it to the side instead of dead center. Your container will look more interesting.

We all know to choose plants that are compatible: Don’t try to mix sun lovers with shade lovers. Still, it’s sometimes hard to remember this basic rule at the garden center when you’ve fallen in love with plants that really shouldn’t share a pot. When in doubt, ask.

Many garden centers carry Proven Winners™. This group of annuals has been developed over the past five years to provide the consumer with an outstanding garden performance including weather tolerance, a long lasting blooming period and desirable growing habits. For example, Bacopa ‘Snow Storm’ is a Proven Winner™ that will bloom nonstop in our hot, humid Connecticut summers. New varieties are introduced every year. For dependable performance, pick a Proven Winner™.

Container plants don’t have to be all annuals. House plants can make great container plants, and there’s nothing that says you can’t plant perennials in pots. Some long blooming perennials include salvia ‘May Knight’, scabiosa ‘Butterfly Blue’, baptisia, coreopsis ‘Moonbeam’ and campanula. Anything that looks interesting can be used. Even shrubs. Try planting potentilla in sunny containers; spirea can take some shade.

Plants with good foliage color and texture will add interest to your flowering plants. These include licorice plant (Helichrysum petiolare) with whitish felt-like rounded leaves and the exotic looking dark purple or lime green foliage of sweet potato vine (Ipomoea batata). Other common choices are English ivies, periwinkles (Vinca spp.) and Swedish Ivies (Plectranthus spp.).
Growing containers in shade is always challenging. Some good shady plant combinations are:
• Caladium, dracaena, impatiens and ivy.
• Coleus, non-stop begonia* and ivy.

Care and Maintenance
Do not water a little bit every day. This is the worst thing you can do to your plants. Instead, observe how fast each container dries out — this will vary over the summer. When the soil surface is dry, water thoroughly, or until water runs out of the bottom of the pot. Don’t water during the heat of the day. Instead, water in early morning or late afternoon, no later than 6 pm so the foliage will be dry during the night. Wet leaves invite fungus and other diseases.

Most people do not water frequently enough. Plants in sunny or windy locations may need water one or more times each day.

Baskets and containers must be fed on a regular basis, every two weeks with a liquid plant food. Look for these numbers on the label: 20-20-20, 15-30-15, or 10-52-10 (a blossom booster). Apply according to the directions on the label.

Ceramic pot feet are usually more decorative than necessary. Most pots will drain just fine without them. However, they would be good under pots in a northern exposure because pots in shady locations drain more slowly.

It’s important to deadhead (cut off the spent blooms) regularly and while you’re deadheading, inspect your plants for signs of insect or disease damage. Insects are attracted to stressed plants, especially plants that receive too much sun and too little water. Diseases are more prevalent in plants that are given too much shade and too much water. Be observant and pick off that insect or that diseased leaf before the disease has a chance to spread to the rest of the plant.

A hard spray of cold water in the afternoon will knock off aphids.

Summer Care
Your container plants will benefit from some extra attention during those dog days of July and August: Give them a “haircut” and mulch the soil surface.

Begin cutting them back about July 4. They will put energy into growing new leaves and this will help them to survive the summer. Also, plants given a haircut will flower better later. The amount to cut back depends on the plant: one to two inches for New Guinea impatiens, four to six inches for heliotrope. Impatiens grown in the shade get very leggy and should be cut back by half.

Plants growing in large containers can be mulched with a one or two inch layer of shredded cedar. This will help to hold moisture in the soil. Be careful not to cover the plant crowns.

So now, after reading this article, I hope you’re all fired up and have complete confidence in yourself to plant something spectacular! Creating your own combinations is always a fun, satisfying and exciting experience.
Mary Jo Bridge Palmer is the second generation at Sam Bridge Nursery & Greenhouses in Greenwich. Mary Jo grew up with a trowel in her hand and delights in teaching others the joys of gardening.

* Non-stop begonias are a cross between the tuberous and fibrous types of begonias. Non-stops are labeled as such at your garden center; it’s a common name that stuck because, like tuberous and fibrous begonias, they flower all summer long. They are large-flowered. All begonias are shade-lovers. However, fibrous begonias, if given enough water, will grow in the sun.

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