Hi, I have moved into an apartment. It is 17 floors up, east facing, with not too much wind. I get about 5 hours of direct sun in the morning I would like to grow flowers and vegetables. Could you please give me some idea of what to grow and the best varieties, how big the containers ought to be (but small enough to bring inside if needed), and what kind of soil I should use. Many thanks.
Hi balcony gardener, what a lovely set of questions! First, may I reassure you that there are numerous books and references on balcony gardening. You could start a brand-new hobby, just reading about this subject. My major piece of advice is to start small. Choose a few containers (maybe three) and build up your expertise and knowledge. Only grow plants that you love, whether we are talking about ornamentals or edibles.
Balcony growing is different from growing in a garden in a number of ways, and I will try and cover the major points. The most important first step will be evaluating the conditions on your balcony. Some of the issues that you should take into account are: temperature; wind, sun and shade; moisture; the size of containers; soil for containers; what plants to grow; and cultural practices (watering and fertilizer).
- Temperature. An area’s hardiness zone number will determine what plants you can grow. Canada uses a formula that consists of 7 climate variables. Canada’s hardiness map is divided into 9 zones (from 0, which is the harshest, to 8, the mildest. The US Department of Agriculture (USDA) bases its system on only average annual minimum temperatures. You can find Canada’s hardiness zone map here; and the US hardiness zone map here. The rule of thumb is that for balconies, you should select plants that are hardy to two zones lower than the zone for your area. That is to take into account the wind and fluctuating temperatures.
- Containers: The containers need to be large enough to help with fluctuations of temperature, water retention, and oxygen, but need to be small enough to be moved inside if needed. These can be bought or, if you know how, easily built. If you plan to have more than a couple of containers, and if you want to grow plants on the railings or up against the wall, you may need to consider your building regulations. Any weight restrictions need to be considered (containers full of wet soil/media can weigh hundreds of pounds depending on their size and what material they are made of). The size of the pot is an important consideration for growing vegetables as well. Guidelines for pot sizes for various vegetables are here and here.
- Soil: A lightweight mix formulated for containers is best. The soil that you use in containers or planters does not have the advantages of a garden bed, which has a rich life of micro- and macro-organisms including our invaluable earthworms that make sure the soil is well aerated. Therefore, make sure that you use a light potting soil. A combination and balance of top soil, vermiculite and compost is ideal. Container pot soil usually needs replacing each year, but if your container is large, replace at least a third of the container with fresh soil.
- Moisture: good drainage is important for your plants to thrive, as is the right growing medium. But if the wind is up, it is very easy for your plants to dry out quickly, so be on the alert for the need to top up your watering to more than once a day. You also need to consider where the run-off water will go; consider your neighbors and their lack of appreciation if your water drops down onto their balcony.
- Plants for container growing: This previous posting on the Toronto Master Gardener site will be useful to you in your choice of what to grow. All of the suggestions are for shady balconies, but are good for all balconies (depending upon the hardiness zone). You can grow annual (great for colour and scent), perennials or all sorts, but if they are tropical, you will need to move them indoors when it gets cold; trailing plants for colour or interest depending upon their leaves; and of course, do not forget herbs and vegetables.
When selecting vegetables, you can select for those varieties that are especially bred for container growing, and for the ability to set fruit with five hours of direct sunlight. For example, most tomatoes need about eight hours of direct sun to set fruit, but if you select for little cherry tomatoes, they will set fruit with five hours of direct sunlight.
- Fertilizer: You will need to get a feel for how much fertilizer your plants need. The light container soil does allow for good drainage, but that may mean flow-through of fertilizer, and more regular fertilizing is required especially for your vegetables. If you see your leaves lose their bright green colour (sign of nitrogen deficiency) then top up with fertilizer (try a slow-release fish fertilizer). Stop fertilizing in the Fall and then resume again in the spring. For more information on fertilizing for containers, see this previous Toronto Master Gardener post.
Good luck with your container balcony garden!
A couple of useful references are:
Colorado State University’s factsheet on container growing can be found here.
The Toronto Master Gardener’s Guide on Container growing can be found here.