Many herbs are well suited to be grown in containers on a balcony. Use cement blocks or bricks to raise the level of some pots, to give an added interest to the configuration on the balcony. This looks much better than just lining pots in a straight row along the edges. With just a little bit of work, the balcony can become an herbal oasis in the city and provide a household with enough herbs to get from one growing season to the next.
Sun and Temperature
Most herbs need six to eight hours of sun each day. A balcony facing south to southeast will satisfy these requirements. Those with northern facing balconies may have to supplement sunlight with grow lights. Herbs require warm temperatures to grow, but they do not like to cook on the balcony. They enjoy 70 to 85 degrees Fahrenheit temperatures but will start to droop above 90 F. They do require more water in extreme heat. When temperatures go below 40 F, the herbs will go into dormancy or die.
Because the pots and soil are above ground the water evaporates quickly. Many herbs are drought resistant and can tolerate a short dry period. Each pot should be checked every morning. If the soil is damp, no water is needed. If the soil is dry, watering is necessary. Plants that droop or wither on a hot afternoon will need to be watered right away.
Plastic pots retain moisture better than clay pots. All pots should have drain holes to expel excess water. All pots should be more than 2 inches deep to accommodate roots systems. A 4-inch pot can only have one plant in it, while an 8-to-12-inch pot can have two or more, depending on the spread of the plant. Most balconies have railings so find a window box that will slip on and plant herbs in it. A 14-inch window box can have two to three herbs planted. Do not crowd containers because the air circulation will be compromised and this can cause disease. Make sure pots have a saucer or drip pan underneath them so water does not drip down on the heads of the neighbors sitting on the balcony below.
Purchase transplants instead of starting seeds. Seeds must be started indoors prior to the warm season and often require special conditions and equipment. About 1 inch of gravel should be placed in the bottom of each pot to ensure good drainage. Pea gravel or plain colored aquarium gravel will do the trick. Herbs do not like their roots to be soggy all the time so drainage is an issue. Fill the pots half full with a commercial potting soil. Use soil with fertilizer mixed in. Plant the herbs and fill the pot up to the top, water and place the pots on the balcony. Herbs do not need to be fertilized until the second year they come back. They will have used up all the nutrients in the soil the first year. Plant several herbs in a large container and mix them up. Plant a large herb like sage or lavender with a small herb like globe basil, then plant a creeping herb that will droop over the sides of the pot like thyme.
Herbs to Plant
Many herbs work well in pots on a balcony. Basil loves heat and parsley is very easy to grow. Both of these will die when it gets cold and need to be replaced the next year. Sometimes parsley will reseed itself but that is rare in a pot. Rosemary, lavender and sage will grow easily on a balcony. Low growing herbs that grow well on the edge of a pot are savory, oregano and thyme. Chives should be planted one plant to a pot because they get very large. Mint should be planted alone in a pot because it will choke out anything else planted with it. Dill and anise are tall plants and have very deep tap roots. They are not generally suitable for balcony growing but can be planted in a very deep pot with some success. Remember that there are many varieties of each of these herbs. There is pineapple sage, cinnamon basil, lemon thyme and many more. It is best to not plant a different variety of the same plant in the same pot, so separate orange mint from spearmint.
Perennial herbs will come back the next year with care. The pots need to be protected during the winter in cold regions. When in the ground plants are naturally protected by the earth around them and the wind and freezing temperatures will not affect them as much. When they are in pots, the plants are prone to dying in the winter because there is nothing to protect them. Store pots in a garage or basement if available. If not, cover the pots with tarp and protect them from the wind with wood or plastic around the bottom of the rungs of the balcony railing. This does not always work in very cold winters and the plants may have to be replaced in the spring. Chives are different. They need a cold snap to be able to grow again when it gets warm. Just leave them out on the balcony all winter.