Whether you don’t have garden space or you want a few mobile crops, planting in containers can be extremely fulfilling and productive. But which plants are best and what do you need to know to create a superb container garden? Read on for our tips on planting, crop selection and troubleshooting your summer container garden.
Container Planting 101
Your new pots are waiting. Your potting soil is ready to go. You’ve gathered seed packets and eager small plants. Now what?
When you’re ready to get your plants going, start by filling your containers with potting soil up to about 2 inches from the top, and water thoroughly. Now you’re ready to plant seeds or baby plants. Planting seeds directly is simplicity itself; just follow the instructions on the seed packet for depth and spacing. Thin extra seedlings with scissors once they sprout.
Moving transplants into containers takes a little more attention. Make sure the potting mix is lightly and evenly damp; thoroughly water baby plants and let them drain while you proceed. With your trowel, dig a hole about as deep as the small containers your seedlings were grown in. Slide out the baby plant and all its soil. Try to keep intact the soil ball around the transplant. If you see a mat of roots twisted at the bottom, untangle them and trim back the longest ones. Fit the plant and its soil ball into the hole, and fill with extra potting mix. Tamp the soil lightly, and move on to the next plant. When everything is in, water the entire container to help plants settle.
If possible, plant transplants when cloudy weather is forecast for the next few days; bright sun is hard on tender transplants.
Best Container Garden Crops
Some of the best plants for a summer container garden include crunchy cucumbers, creamy eggplants, colorful peppers and juicy tomatoes. Follow these tips for growing each warm-season treasure in containers.
• Start in containers as transplants.
• Plant eight weeks before daytime highs reach 80 degrees.
• For the first couple of weeks, protect tender plants with plastic sheeting, held up off plants with short stakes; or cover them with milk-jug cloches at night.
• Put the container in your sunniest location, keep soil moist, and fertilize every two weeks.
• As soon as the outside skin is glossy and smooth, cut off eggplants, taking a bit of the stem. To keep plants producing, keep up with harvesting.
• Traditional eggplants can be too heavy for containers. Explore Asian types and dwarfs. Varieties to try: ‘Asian Bride’, ‘Green Goddess’, ‘Ichiban’, ‘Neon’ (Asian types); ‘Bambino’, ‘Comprido Verde Claro’, ‘Little Fingers’, ‘Rosa Bianca’ (dwarf types)
• Start in containers as transplants. Wait until nighttime temperatures are consistently above 55 degrees and daytime temperatures are at least 70 degrees.
• Choose dense, compact young plants—not tall and leggy ones. Don’t be seduced by large plants with flowers or tiny fruits already showing.
• Keep peppers warm: While plants are getting established, position containers where they get maximum sun. If weather is marginal, cover plants with a row cover until they flower.
• On the other hand, in a heat wave (mid to upper 90s), move into the shade any pepper plants that already have fruit.
• Peppers respond well to phosphorous-rich fertilizer. Mix a bit of superphosphate, bone meal or bulb food into the soil at planting time. Calcium, magnesium and sulfur are also important. Common household sources you can bury in your container include matches (sulfur), eggshells (calcium) and Epsom salts dissolved in water (magnesium). Do not give plants extra nitrogen.
• Early in the season, harvest green peppers when they reach a nice size. The more you pick, the more you’ll get.
• Later in summer, let peppers hang on until they reach their mature color.
• Any pepper variety, sweet or hot, should do well in containers. Varieties to try: Sweet: ‘Ace’, ‘Giant Marconi’, ‘Gypsy’, ‘North Star’ (red); ‘Cherry Time’, ‘Jingle Bells’, ‘Sweet Red Cherry’ (mini reds); ‘Valencia’ (orange); ‘Golden Summer’ (yellow); ‘Lilac’, ‘Purple Beauty’ (purple); ‘Chocolate Beauty’, ‘Sweet Chocolate’ (brown) Hot: ‘Senorita Jalapeño’, ‘Super Cayenne II’, ‘Super Chile’, ‘Thai Dragon’
• Cucumbers grow fast. Start with seeds rather than transplants.
• Cucumbers are vines, but several types maintain a compact bush shape; be sure you know which you’re getting.
• Plant when daytime temperatures reach at least 70 degrees.
• Consistent water and weekly organic fertilizer are the secrets to success. To help hold in moisture, cover soil with light moss.
• Cukes do well on a trellis. In a 20-inch container with a demi-cage, you could plant six vines.
• Pick cucumbers while they’re small and tender or the vines will shut down.
• If your area is not visited by many pollinators, help plants by visiting the garden in the morning with a small paintbrush. Swirl it around inside an open flower. Then go on to the next blossom, just like a bee.
• Focus on slicers instead of picklers. (Pickles require more cucumbers than containers can reliably produce.) Varieties to try: ‘Fanfare’, ‘Lemon’, ‘Salad Bush’, ‘Suyo’, ‘Sweet Success’
• Start in containers as transplants. If you don’t grow seedlings yourself, choose plants that are stocky with thick stems and rich green leaves.
• Determinate tomatoes grow to a certain height then get no taller, and yield fruit in a concentrated time span. Rambunctious indeterminate tomatoes grow until frost kills them; provide good support such as a stout stake, trellis or demi-cage set a foot deep into the soil.
• Plant seedlings when nighttime temperatures stay above 55. Use large containers. Heavy feeders with large root systems, tomatoes need plenty of soil.
• Use liquid complete fertilizer every two weeks, or apply a new dose of time-release fertilizer midway through the season. Don’t use nitrogen-heavy fertilizer. An application of liquid seaweed every two weeks yields excellent results.
• Water consistently and deeply. Dry spells followed by intense watering can lead to cracked fruits.
• Plant tomatoes deeply, covering up the lowest sets of leaves, to encourage vigorous root growth. Add a weak solution of complete fertilizer or fish emulsion to the soil around new plants.
• Use these general rules when choosing varieties: Smaller fruits are ready sooner; determinate varieties are easier to manage; plant at least one reliable mainstay such as ‘Big Beef’, ‘Celebrity’ or ‘Early Girl’; and experiment with other varieties as space allows.
Troubleshooting the Container Garden
With a little ingenuity, you can enhance the physical environment around your containers. Most vegetables need six hours of sunlight a day, so make sure wherever you plan to put your containers gets at least that amount.
• Too much sun. Suspend a shade from an overhang. Or plant a trellis with beans and position it so it faces the sun; put shade-loving plants at the base of the trellis.
• Too little sun. Paint a wall or free-standing screen bright white and position containers where they’ll catch the light that bounces off.
• Too hot. When container soil gets too hot, roots suffer. If your summers are hot, stick to larger containers, which retain moisture better. To add a layer of insulation, put one plant-filled container inside a larger container and fill in the gap with peat moss or wood chips, kept damp.
• Too cold. If your growing season isn’t long enough, gain time by babying containers through cool days. Wrap pots in blankets or heavy dark fabric. Use dark containers (or paint those you have). At night, cover the entire container, plants and all, with lightweight protection such as a pillowcase or row cover.
Adapted from McGee and Stuckey's The Bountiful Container by Rose Marie Nichols McGee and Maggie Stuckey.