Spring gardening with a pinch of precaution
If you have a lot of digging to do in your garden, it's important to have your utilities located before starting the work. In the suburbs, call J.U.L.I.E. at (800) 892-0123 or dial 811 to have your yard marked for underground utilities (this is a free service). The group's website is www.illinois1call.com.
In Chicago, call DIGGER at (312) 744-7000.
It generally takes two working days for these services to locate your utility lines, so allow plenty of time before digging. These locating services will not mark any lines you have installed yourself, such as a gas line to a grill or wires for landscape lighting.
Dig carefully by hand if you are working within 18 inches of either side of any marked underground utilities. Cable television and phone lines tend to be very shallow - 1 to 2 inches below the surface. Also, be careful when digging in gardens with underground sprinklers. Black polyvinyl piping used in many irrigation systems is very easy to cut with a spade.
• Be sure to keep the average last frost dates for your area in mind as you consider any early planting of cold-sensitive plants. The Chicago Botanic Garden's average last frost date is May 15.
It is best not to install tropical plants or warm-season annuals and vegetables early unless you can be sure the weather will not reach freezing or even have extended periods of time in the 40s. There are plants such as impatiens and coleus that can be badly damaged or killed by a frost. They can also be set back by extended periods of cold and wet weather, which may require them to be replaced.
Warm-season vegetables such as tomatoes also will not do well in typical early May cold spells, so do not buy them until later in the month, even though you may find them for sale. Go ahead and plant trees, shrubs, perennials and ground covers.
• It's a beneficial garden practice to deadhead (manually pinch off spent flowers) rhododendrons and azaleas after they finish flowering. This is also the correct time to prune their branches to reduce the size of the plant as needed.
It is best to be conservative with pruning them back. You can increase the flower count for the following year by very carefully pinching off one-half of the sticky new green growth emerging from the area where the flowers were generated.
• Prune off any dead branches on evergreens. They will be easy to spot with brown leaves at this time of year. Most evergreens, such as yews, boxwood and arborvitae, are slow to fill back in, so take this into consideration as to whether is it better to buy a new plant.
• The weather has continued to be cool and rainy for the most part, so continue to avoid working in wet areas of your garden.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.