Get your yard, flower beds ready for May 15
If you haven't cleaned up your garden yet, it is OK to continue removing garden debris from beds and cutting back perennials. The perennials will have begun growing so be very careful when cutting them back and removing debris to avoid damaging new shoots.
Cut perennials back higher above ground to avoid damaging the new growth. It's best to avoid walking about in garden beds when the soil is wet to avoid compacting the soil.
• Many garden beds have irregular edges. Beds will look better and be easier to mow along if they have smooth, flowing curves.
Use a pliable garden hose or rope to lay out your new bed line. Use marking point to mark the line or use a spade with the rope or hose as a guideline to cut the new edge. All clumps of grass should be removed from the bed and any clods of soil should be broken up and spread around.
Avoid the "volcano effect" around trees, which is caused by piling soil and mulch up around the trunk. Neaten up your perennial beds by top dressing with a light layer of mulch no more than an inch deep. I prefer leaving some of the leaves that fell last fall in my perennial beds for more of a natural look and to same time with clean up.
• Apply fertilizer to garden beds, if needed. This is likely not so necessary if you regularly mulch the beds or leave leaves on them. Most gardens in the Chicago area have soils with adequate levels of phosphorus so choose a fertilizer with little or no phosphorus.
The higher the percentage of nitrogen in the fertilizer you purchase, the less you will need to apply to your garden. Follow instructions on the bag or ask a salesperson for advice. Have your soil tested if you want to be sure of what the best fertilizer would be for your garden. Use soil from a few locations to mix together for a good composite sample. If your garden is large, then break up your property into sections and send in multiple samples.
• Continue planting annuals that are cold tolerant to add color to your gardens. It's best to avoid planting annuals such as petunias until after the danger of frost has passed in your area. The average last frost at the Chicago Botanic Garden is May 15.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.