Ask a Master Gardener: Plant iris in light, loamy soil; save dividing for July

Q. I have a question regarding subdividing bearded iris. Can you please let me know what needs to be done to prepare the planting bed for bearded iris after dividing them.

A. Iris will grow in many soil types but a light, loamy soil with a pH of 6 to 7 is preferred. If you have heavy soil, adding compost — or other organic material like well rotted cow manure.

Wait until after they flower to divide, July to September is better than spring. People often plant these too deep. Plant your divided rhizomes at or just barely below the surface, so the tops can be seen and the roots down, spread out over a small mound of soil.

Fertilization of iris depends on a soil test result, but must be done in moderation. Nitrogen, potash, and phosphorus are essential, but excessive nitrogen promotes lush growth that is more susceptible to rot diseases. Applying a low-nitrogen fertilizer such as 5-10-10 in early spring will result in stronger plants for later division.

Q. What is the best time to cut off the flower stalk on a yucca plant?

A. Yuccas are notable for their rosettes of evergreen, tough, sword-shaped leaves and large clusters of white or whitish flowers. They are also extremely hardy and not demanding. Remove flower stalk after blooming. This will encourage new growth.

Q. Recently we ran an article about weed control. A writer wrote and was concerned that the toxic newsprint may leach in the ground.

A. Since most newspaper inks are soy-based, they are fine to use. On the other hand, glossy inserts may use inks with lead or other heavy metals that may leach into the soil. Therefore, use only standard newsprint and discard glossy advertisements.

Ÿ Provided by Mary Boldan, Mary Moisand and Donna Siemro, University of Illinois Extension Master Gardeners. Send questions to Ask a Master Gardener, c/o Friendship Park Conservatory, 395 W. Algonquin Road, Des Plaines, IL 60016, (847) 298-3502 or via e-mail to cookcountymg.com@gmail.com.