Add sulfur to soil to turn pink hydrangeas blue
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 work at turning the flowers back to blue. The flowers turn pink in more alkaline soils. Add 3 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.
• 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 will thin out over time and will need occasional replenishing for a consistent year-to-year display.
Observe your garden over the course of spring and early summer and make a 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 about the garden - they are easy to spot when they are in flower.
• Many trees are planted too deeply. To determine the proper planting depth for your new tree, locate the trunk flare, which is the place where the trunk widens at ground level. If the trunk flare is not showing, open the burlap to find the flare. You will need to plant the tree higher in the hole and very carefully remove the excess soil above the roots to expose the flare.
Generally, planting 2 to 3 inches higher than ground level is a good idea in heavy clay soils. It is best not to amend the backfill going back in the planting hole but it is OK to amend the soil at the surface around the tree. If the root ball appears to be loose, it is best to 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.