What Gardening Zone Is Illinois

With Chicago's frigid winters and sizzling summers, there are four things local gardeners need to be aware of in order to ensure a healthy Chicago landscape year after year. Whether you are sprucing up your garden beds or completely overhauling your landscaping, following these basic principles will offer you the best results.

1) Choose plants that grow well in the Chicago climate

Plants need to be able to survive the frigid area winters in order to thrive and bloom for years to come, so make sure to check the zone hardiness of the plants you are considering by referencing the USDA Hardiness Zone map. Each zone represents a range of the coldest average annual temperature for that area. Chicago falls into zone 5, with a low average temperature of -20°F to -10°F. More often than not, you will find a label on plants indicating that the plant is "hardy up to zone x." Additionally, websites often categorize plants by zone. Be aware that if you choose plants with a higher zone number than the zone in which you live, the odds are that they will neither thrive – nor survive.

Anne Roberts Gardens USDA-hardiness-zones Although not definitively as detrimental as cold, the heat also affects plants. As a general guideline, the American Horticulture Society has created a Heat Zone Map to help in selecting plants that will thrive in your area. The map is divided into 12 zones. Each zone is based on the average days of the year when the temperature is above 86° F. Chicago falls in zone 5 with an average of 30 to 45 days. While not all nursery plant tags currently display the Heat Zone recommendation, doing so is becoming more popular. Keep in mind this is a general guideline. Variables related to temperature can and do affect your plantings, such as how much shade or breeze a specific location might have.

Anne Roberts Gardens heatzonemap

Now that you've selected plantings suitable for your zone, be aware that just because a plant is in your hardiness and heat zone, that doesn't mean it will grow well in your location. The other factors that must be considered are:

2) Amount of Sunlight

It is important to observe how many hours of sunlight the area you are planting gets each day. When we talk about sunlight, we are not talking about heat but the amount of direct sunlight a plant requires for photosynthesis to occur. Clearly, different plants thrive with different amounts: Some don't require much, if any, direct sunlight, where others need all they can get. To help you choose the right varieties for your location, plants are usually labeled as low/shade, medium/partial sun or high/full sun. Low or medium-shade plants usually only need a little to a few hours of sunlight, but high/full sun plants need at least eight hours of sunlight a day. Without adequate sun exposure, leaves may be small or turn yellow/brown – and variegated leaves will lose their variegation. Too much sun and your plants will burn. So double check the amount of sunlight the plants you are considering need before planting them.

3) Soil Considerations

If you are planting in an area that you haven't had much luck with in the past, you might want to have the soil tested. Plants generally prefer a neutral balance of alkalinity and acid. On the pH scale, that is around 7. If your pH is low (below 6), the soil is too acidic and you can add some limestone to neutralize it. If your soil's pH is above 7.5, it is too alkaline, which is typical of Chicago soil. You can add sulfur to bring the pH down.

You will also want to check the soil levels of nitrogen, potassium and phosphorus. These are the nutrients plants thrive on. The mix you'll use to feed your plants depends upon your plants and the stage at which they are growing. You can adjust your soil with fertilizer from your local nursery or home improvement store. On fertilizer packages, you will normally see a series of three numbers, such as 10-10-10. These numbers correlate to Nitrogen – Phosphorus – and Potassium, and indicate the mix of the fertilizer blend. Joe Lamp'l, the host of the PBS show "Growing a Greener World" has a great article titled "The Numbers on Fertilizers Labels, What They Mean", which describes the benefits of each of these nutrients. Learning to properly feed your plants is not difficult once you take the time to understand their needs and what the fertilizers offer.

Another way to feed your plants is with organic matter, such as compost from your kitchen or yard, with manure or with peat. This method also helps with soil aeration (softening the dirt and loosening it up), which is a plus with Chicago's hard clay soil.

To have your soil tested, contact one of these testing labs listed by the University of Illinois. Testing fees are generally less than $40 per sample.

To learn more about the requirements of specific plants, Landscape expert David Beaulieu has compiled a plant database categorized by common names that contains all the information you'll need to know.

4 ) Rainwater Runoff

While it may seem obvious, considering the wetness of your soil is essential. Ponding water – water that sits in an area – can erode both the soil and the root system, promoting fungus growth and attracting insects and bugs that can be harmful to your plants and your environment. Heavy water run-off or sitting water can adversely affect a plant's root system by compacting the soil around it and not allowing the plant to breathe and by eroding the soil itself or by washing away many of the necessary nutrients in it.

One common but overlooked source of excessive rainwater to a garden area is from gutters. Installing a drainage system can alleviate the issue if there is a good place to divert the water. One solution we often recommend is to simply use rain barrels, which collect the runoff in a sustainable solution that saves money. Check out Anne Roberts' article "8 Benefits of Rain Barrels" to learn more about them.

If you are looking for creative landscaping ideas to modify for your home, we recommend Houzz as a great website for inspiration for beautiful garden and landscaping designs. You can even filter their pictures to see images from the Chicago area. Another great resource is Anne Roberts Gardens Portfolio.

To recap, if you keep these four basic considerations in mind – properly zoned plants, suitable sunlight, nutritious soul and proper moisture – before planning your Chicago landscaping project, you will be off to a fabulous start in creating and maintaining a beautiful garden for years to come.