Thriller, Filler, Spiller

How to Design and Grow Dramatically Beautiful Container Plants

By Joshua Fuder

Container gardening can serve as a terrific first step into gardening for the novice; its also ideal if youre limited on time or space. Additionally, its excellent for aging gardeners or anyone with limited mobility because it puts the soil at a height that is more easily accessible.

Success Starts with the Soil
The biggest difference in container gardening vs. in-ground gardening is the soil. Commercial potting mixes are ideal for container gardening because they allow for adequate drainage and aeration. These mixes will contain a combination of vermiculite and peat moss and either perlite or ground-pine bark. Many commercial mixtures also come fortified with fertilizer. If you plan to have an abundance of containers, consider mixing your own potting soil to save money. Mineral soil (soil from your garden) can be used as long as its improved with organic matter to provide the necessary drainage. A mixture of two parts soil, two parts peat moss and one part perlite should be satisfactory.

Fertilizer Amendments
Although commercial mixtures that come fortified with fertilizer often claim to feed up to four months, potting soils by design will not hold on to nutrients for more than a few weeks. Nutrient levels drop as plants use them for growth, and with each watering, nutrients are leached through the soil.

Most commercial fertilizers contain the big three nutrients nitrogen, phosphorus and potassium. These are the primary nutrients required for plant growth. There are other minor nutrients required for healthy plant growth that are usually found in sufficient amounts in native soils. Since potting mixtures dont contain real soil, they will often lack minor nutrients like calcium, magnesium, sulfur and iron.

Container-grown plants may turn yellow due to lack of iron, magnesium or sulfur. A container-grown tomato may get blossom-end rot, which is a symptom of calcium deficiency. The solution is to choose fertilizers that contain both major and minor nutrients. You can also add dolomitic limestone to the potting mixture at planting time, as it contains both calcium and magnesium. Apply one tablespoon of lime per gallon of soil mixture.

When mixing your own soil, its beneficial to add a premium-grade fertilizer. A well-balanced fertilizer such as 5-10-15, 5-10-10 or 6-12-12 at a rate of five pounds per cubic yard or 3 ounces per bushel (1.25 cubic feet). Dolomitic lime should also be added at the same rate as the fertilizer.

Supplemental fertilization of plants should begin two-to-three weeks after planting. The frequency will depend on what type of fertilizer you choose. For liquid-soluble fertilizer, plan to apply it every two-to-three weeks during the growing season. For dry, granular types, apply a half teaspoon for every gallon of soil every two-to-three weeks. Slow-release fertilizers are a good option and will last up to three months. A teaspoonful per gallon of soil is generally recommended.

Creative Containers
Containers come in all shapes and forms, from colorful, beautifully glazed pots to old rubber boots.  Beauty is in the eye of the beholder, but the function is the same. The most important consideration is whether it has adequate drainage. If you choose a pot without holes for drainage, its recommended to use a double-pot method. This requires that you pot in a different container that has drainage holes then place it on gravel inside the pot without holes.

Container size is also important. Outdoor container plants, especially fast-growing ones, need adequate space for root development. Small pots restrict root growth, which will result in limited top growth. Containers that are tall (more than one foot) will require a large amount of soil. To save on soil, you can fill the bottom of containers with light-weight material such as aluminum cans or old nursery pots placed open-end down.

Planting Design
Designing the container planting is much like traditional garden design. Principles like form, texture, color and proper proportion are perhaps more important in containers than in a larger landscape. For a balanced look, dont let plants be more than two-thirds of the overall height of the container. For shallow or small containers, choose smaller plants or plants with small foliage. For large or tall containers, choose plants with medium-to-tall, mature-sized plants, plants with large leaves or both.

Successful plantings will pull the eye to the center to a thriller plant. Plants that work well in this role have compact, upright growth such as salvia, grasses and Dracaena spike.  Around the thriller, you want to create a sense of flow, so complementary fillers should be used. Filler plants will have a compact, upright growth. Good examples of filler plants are geraniums, Dusty Miller and heliotrope. To get a lush, overflowing look, add additional plants that will serve as the spiller. Plants like sweet potato vine, verbenas, Vinca vines or Portulacas will be sure to impress.

Joshua Fuder is an agriculture and natural resources agent at the UGA Cooperative Extension Cherokee County. Contact the UGA Extension office for any gardening assistance, 770-721-7830 or CAES.UGA.Edu/extension/cherokee