Small is beautiful. When perusing seed racks, packets, and catalogs, have your young gardeners identify words and phrases that fit the small-space bill: compact, bush (especially with squash varieties), for containers, tiny, dwarf, and so on. Visit here for a chart of some species and varieties recommended for containers.

Consider climate. Pay attention to planting dates for your climate and frost-free period as you would with any outdoor garden. The benefit of containers is that you can move them in or under cover if frost or cold temperatures threaten (assuming they're not too heavy). But selecting plants adapted to your climate will reduce your effort. Plant for the seasons. Some plants thrive in the cool temperatures of spring and fall but fade in midsummer heat. Others thrive in the hottest weather. In warm parts of the country there are three distinct growing seasons. Choose cool-season plants for your spring containers. When they begin to look tired in the heat, replace them with heat-lovers. In fall, switch back to the cool-season plants.

Select for sunlight. Choose plants according to the amount of sun available in your prospective container garden location. Most vegetable and herb plants you're likely to grow need at least six hours of sunlight each day. Leafy vegetables such as spinach, cabbage, and lettuce can tolerate a bit more shade; flowers vary. Check catalogs and seed packets. (If students experiment by moving containers to maximize their daily sunlight, they'll also learn something about the relationship between the Earth and the sun!) Our lesson, Hello Sunshine!, walks you through this process.

Consider companions. Plan to put plants with similar needs (e.g., sun, shade, water, or fertilizer) in a given container. The most important considerations are light and moisture preferences. Mixing plants with different needs in a single container is a recipe for disaster. For aesthetic purposes, select plants with different growth habits. Tall, spiky plants, like grasses or snapdragons, provide a vertical element for the center or back of the planter. Smaller, mounding or shrubby plants provide substance at mid-height. And cascading plants soften the edges of the planter.

Go vertical! Some schools, particularly those in urban areas, have saved space and created delightful nooks by growing container plants vertically. Consider creating garden vessels for vining plants such as pole beans, cucumbers, gourds, morning glory, clematis, sweet potato vine, star jasmine, or passionflower. Challenge students to create a trellis or supports and to figure out how to keep an upright plant jungle well watered and fed. Do they notice any patterns in how plants climb or how tendrils function? Can they coax the plants to change direction?

Life Span Matters

Students want to try growing an orchard on the blacktopped playground? Or think houseplants would look snazzy in barrels outside the school's entrance? This section and accompanying chart will help students explore the life span and mature sizes of these plant options, consider if they're feasible. Maybe they'll be inspired to devise a way to keep fruit trees alive through a northern winter!

Annuals. Many annual flowers have compact root systems and grow well in relatively small containers, provided you give them adequate water and fertilizer. Since you'll be discarding them at the end of the growing season, you don't need to worry about their long-term health. Any container smaller than 8 inches in diameter will dry out quickly, but as long as you are prepared to be diligent in your daily care you can go even smaller. You've probably seen annual flowers planted in all sorts of odd containers, from discarded tires to old boots!

Vegetables. As a general rule, for optimum production vegetables require somewhat larger pots than ornamental annuals. Tomatoes, for example, grow well in 5-gallon buckets, though some compact varieties have been bred to thrive in smaller confines. Peppers and eggplant will thrive in 2-gallon containers (about 8 inches in diameter and 10 inches tall). If you plan to grow root crops, choose pots that can accommodate the mature size of the root. For instance, beets need 8 inches of soil, but full-size carrots need 12 inches.

Perennials, shrubs, and trees. Because these plants remain in their containers for more than one growing season and may have to weather some extremes of heat and cold, their roots need lots of room. Know how the mature size of the plant; that small daylily or hosta in the 4-inch nursery pot may eventually fill a half barrel planter. Where winters are mild to moderate winters many perennials need minimal winter protection. It's a different story in cold regions. Even plants that are hardy in your zone can suffer root damage if the soil in the container freezes solid or if alternating freeze/thaw cycles cause the soil to heave. Be prepared to provide winter protection. Learn more about winter protection in Planting and Maintenance.

Plant Characteristics at a Glance Annuals · Live for one season; do not overwinter (can plant in decorative containers that could be damaged by winter weather) · Must be replaced each growing season · Those with compact root systems adapt well to small containers · No dividing necessary · Includes a huge number of flowering plants and vegetables Perennials · Live for two or more years · Resprout each spring from overwintered roots · Peak bloom often lasts a few weeks; may bloom sporadically throughout growing season · More extensive root systems require generously sized containers · Must use weather-proof containers · May need dividing every few years · May need protection to survive harsh winters Trees and Shrubs · Live for more than two years · May be deciduous or evergreen · More extensive root systems require generously sized containers · Must use heavy containers to accommodate heavier top mass · May need pruning to maintain manageable size · May need protection to survive harsh winters · Place on casters or a special plant dolly before planting if you need to move it

 

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