Add sulfur to your soil for more beautiful displays
If your soil is too alkaline, elemental or granulated sulfur can be added to lower the pH. Rhododendrons and azaleas are examples of plants that can benefit from sulfur applications in many gardens in the Chicago area.
Apply sulfur to your blue hydrangeas if they are turning pink to turn the flowers back to blue. The flowers turn pink in more alkaline soils.
Add three pounds of sulfur per 100 square feet of garden area per year. It is best to apply in the spring and fall, applying one-half of the recommended rate each time.
Work the sulfur into the soil and water in. Sulfur is slow-acting. Wear protective gloves and be careful to keep the dust out of your eyes when applying.
• Many boxwoods were damaged by last winter's weather and the brown foliage has now become very obvious in gardens. A lot of the plants I have seen are in bad shape with limited live foliage deep in the plant.
Cut these plants back to the live foliage and wait for the plants to fill back in over the next few years. The amount of time for a particular boxwood to recover will vary depending on the health of the plant and extent of damage, but you should count on at least two to three years for it to fill back in, as boxwood is a slow-growing plant.
• Take photographs of your bulb displays now and throughout the month as they come into flower and make notes as to where new bulbs can be added in fall to improve the display.
Some bulbs thin out over time and need occasional replenishing for a consistent year-to-year display. Observe your garden over the course of spring and early summer and plan to add bulbs that bloom at different times to extend color. This will make it much easier when you are ordering and planting bulbs later this year.
Remove any rogue bulbs that may have seeded themselves around the garden.
• Many trees are planted too deeply. To determine the proper planting depth for your new tree, locate the trunk flare, which is where the trunk widens at ground level. If the trunk flare is not showing, open the burlap to find the flare.
Plant the tree higher in the hole and very carefully remove excess soil above the roots to expose the flare. Generally, planting 2 to 3 inches higher than ground level is appropriate in heavy clay soils. It is best not to amend the backfill returning to the planting hole, but do amend the soil at the surface around the tree.
If the root ball appears to be loose, remove the wire basket and burlap after the tree is positioned in the planting hole.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.