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Begonias, such as this Skaugum Begonia, are well-suited to containers.
Growing in containers saves space, but it's also a smart alternative if you are restricted by too much shade, poor soil, too little time, limited mobility or a difficult climate. Container gardens can be much more productive than a regular garden while allowing you to avoid most pest and disease problems. Best of all, it brings your garden right up close, creating a sense of intimacy that you don't get in an ordinary backyard garden.
Almost anything can serve as a container for growing plants. In addition to terra cotta, plastic or pressed fiber pots, you can use recycled whiskey barrels, 5-gallon food buckets, bushel baskets, plastic tubs, wooden planter boxes, even old tires! Self-watering planters, which have built-in water reservoirs, are great innovations.
The size of container that you use should be determined by the plants you plan to grow. Begonias may get by in a 6-inch deep container, but don't try to grow a canna in a container that holds less than 3 gallons of soil. The general rule is to use the largest container possible, because the more soil there is, the more root space there will be—and the longer your plants can go between waterings.
Make sure the containers have drainage holes—on the sides rather than the bottom if possible—so excess water can drain and roots won't get waterlogged. For large pots with drainage holes on the bottom, elevate the pots on bricks or scraps of wood so that the water can escape.
In general, a 20-gallon pot should have four to six 3/4-inch holes; a 30-gallon pot should have at least eight 1-inch holes. You can put stones or bits of crockery in the bottom of the pot, but with a well-aerated soil mix, this is unnecessary and will only steal valuable root space.
Once you have chosen the right container, you are ready to pick a soil mix. Soil for container-grown plants should be light and friable, well drained and moisture-retentive. Garden soil is much too dense and can introduce disease and insect problems. Most container-grown plants are happiest in a soilless blend comprised of sphagnum moss, vermiculite or perlite, with the addition of finished compost.
Because they bloom constantly, Topmix Dahlias make ideal windowbox plants.
Because they bloom constantly, Topmix Dahlias make ideal windowbox plants.
It's easy to purchase a pre-mixed blend, but you can also create your own mixes, using the following recipes as a guide.
Organic Blend: 5 gallons finished compost, 1 gallon builder's sand, 1 gallon vermiculite or perlite, 1 cup granular-all purpose organic fertilizer.
Standard Blend (Cornell Mix): 1 bushel vermiculite, 1 bushel ground sphagnum moss, 8 tablespoons super phosphate, 8 tablespoons ground limestone, 2 cups bone meal.
Light Blend (for rooftops): 5 gallons ground sphagnum moss, 5 gallons vermiculite or perlite, 2 gallons compost, 1 cup granular all-purpose fertilizer.
Any soil mix will become compacted over time. If your containers seem water-logged and heavy, you may need to replace your soil mix at the start of a new growing season with a fresh mix.
If you go off to work in the morning without watering your windowboxes or patio containers, you are likely to come home to droopy, if not dead plants. When plants get too dry, their delicate feeder roots die and the plant must concentrate its energy on re-growing damaged roots rather than producing fruit or flowers.
That means unless you use self-watering planters or have a drip-irrigation system, you'll probably need to check on your plants daily, and maybe even twice a day if the weather is really hot. If you have more than a few planters, and especially if you travel, a drip-irrigation system is ideal.
Three Watering Innovations for Containers
Because most potting mixes provide few nutrients, your plants will be totally dependent on you for their food. Add granular organic fertilizer at planting time, then water weekly with half-strength, water-soluble fertilizer. Foliar feed with seaweed or fish emulsion for a quick pick-me-up if your plants look stressed or have been cut back.
Each week during the growing season, remove spent flowers and pinch back leggy stems. When necessary, replace tired plants with some fresh annuals, especially late-season favorites, such as ornamental kale and mums.
If you plan to overwinter some of your potted plants, they should be cut back and put in a cool location. Water sparingly and do not fertilize until spring. Once warm weather arrives, remove plants from their containers, tease away old soil, and repot the plants in a fresh soil blend.
Some sort of vertical support is a necessity for container-grown tomato plants, cucumbers, and flowering vines. Trellises can also add a beautiful vertical accent when covered with morning glories or sweet peas. Keep the scale of the trellis in proportion to the pot, and be sure to attach it securely using brackets or wires. Losing a mature tomato plant or flower-covered trellis to an August thunderstorm can be heartbreaking.
This planter has been layered with bulbs, which ensures a longer season of bloom.
If you are short on garden space or do not have access to a garden, you can still enjoy the beauty of spring-flowering bulbs. Most spring-flowering bulbs can be grown in a container as well as in the garden. To be successful requires some special attention, but the colorful spring results are well worth the effort. The one essential step is to expose the potted bulbs to at least 12 weeks of temperatures between 32 and 45 degrees F.
You can choose your own bulbs, or, to make things simple, you can use Dutch Gardens' Bulb Beds for Pots. The planting trays are made to fit a 10- to 12-in. pot.
Choosing a Container: The size of container that you use should be determined by the number of bulbs you want to plant. Regardless of the diameter of the pot, we recommend using a container that is at least 8 inches deep. Make sure the container has drainage holes—on the sides rather than the bottom if possible—so excess water can drain and roots won't get waterlogged. Self-watering pots are not recommended for growing spring-blooming bulbs.
Choosing a Potting Mix: Once you have chosen a container, you are ready to select a soil mix. Soil for container-grown plants should be light and friable, well drained and moisture-retentive. Garden soil is much too dense and can introduce disease and insect problems. Your bulbs will grow best in a soilless blend comprised of milled sphagnum moss and vermiculite or perlite, with the addition of some finished compost.
Drainage: When spring-blooming bulbs fail to flower, it's most often because the bulbs have been too wet during the winter. To ensure good drainage, we recommend lining the bottom of your container with an inch or two of stones or pieces of broken pots. Make sure that excess moisture can drain away so the pot is never in standing water.
Start by placing several inches of potting mix on top of the drainage material. Big bulbs, such as tulips and daffodils, should be planted 6 inches deep. Smaller bulbs, such as crocuses and muscari, need to be about 3 inches below the soil surface. Place enough soil on the bottom of your container to allow for the proper planting depth of your bulbs, taking into account that the finished soil surface should be about 1-inch below the top of the pot.
If you will be planting more than one type of bulb in the same container, plant the bulbs with the deepest planting requirement first (tulips and daffodils), followed by an inch of two of potting soil. Then add the bulbs that have shallower planting requirements (crocus and muscari). This planting technique, called layering, will provide you with a succession of blooms and give your container a very full look.
Watering: After planting, water the container thoroughly. Don't allow the soil to dry out completely during the winter. If you don't receive enough rain to moisten the soil or if you are storing the container in a covered area, such as a shed or garage, water the container regularly enough to maintain "barely moist" soil-about once a month.
Cold Protection & Cold Treatment: For proper flower formation, spring-blooming bulbs must be exposed to a minimum of 12 weeks of temperatures below 45 degrees F. If you are growing spring-blooming bulbs in containers, here are a few things to keep in mind: