“I just moved to a home with very limited garden space, but with a large patio. I would like to try gardening in containers this summer. Can you provide advice on getting started?”
— Abigail Jackson, Morton Grove
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There are many different types and styles of containers to choose from for your patio. The pots themselves can be decorative or very simple, so choose which ones best suit your personal taste and design requirements.
The size of the pots you purchase should be in scale with the surrounding landscape. The bigger your garden space, the bigger the container you will need to look right. For example, small containers sitting by themselves on a large patio or deck will look out of place, while working just fine when combined with larger pots.
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Small and shallow containers will dry out more quickly, especially later in the season when the plants are established, and root bound. When using small pots in sunny locations, you will need to pay close attention to watering, especially during hot weather. Consider using a mix of different sizes of pots grouped together to add interest and the capacity to layer plants from taller to shorter.
Whichever containers you choose, it is essential to have a drainage hole or holes in the bottom of them; otherwise, water will build up in the containers and drown your plants. The holes do not need to be large, but there must be enough holes so excess water can drain out. If a container has no holes, try drilling some yourself.
A container without holes is best used as a cover to hide a plain pot or to grow aquatic plants in. Adding gravel at the bottom of a pot will not improve drainage but can add weight to a lightweight container in a windy location where more stability is needed. It is important to use a soilless growing medium designed for containers — your local garden center will have bagged growing medium for sale.
Do not use garden soil in your pots. Garden soils used in containers, even when mixed with compost, will generally be slow to drain and be poorly aerated, causing plants to perform poorly.
Bags of growing medium are typically sold by cubic feet. Estimate how much you need by calculating the volume of your container. For square pots, multiply length, width and height. For round pots, multiply 3.14 (pi) and the radius of the pot’s diameter times the height of the pot. All units of measure need to be in feet to give you the amount of cubic feet of growing medium to purchase. Convert inches to feet by dividing by 12 (inches per foot). I like to purchase a little extra medium to be sure that I have enough. You can also just guess how much to buy.
If you have large containers and want to save money by using less growing medium, use empty plastic pots turned upside down in the bottom of the container to fill in space. I have also used crumpled up bags that the growing medium and compost are sold in as filler, too. Styrofoam peanuts will work, but create a mess when the time comes to clean out the containers.
I like to have at least a foot of depth of medium above the filler at the bottom of the pot — use a greater depth if you are planning to grow very large plants or shrubs in your containers. Gently firm the planter mixture as you fill the container. Do not fill the medium level to the top of the pot, as you will need about an inch gap to the top of the pot to make watering easier — use less space for small pots, while more space is better for very large pots. The growing medium should be slightly moist as you are planting.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.
