Extension News

Ask the ISU Experts

Bearded Irises

Note to media editors: Got gardening questions? Contact the Hortline at (515) 294-3108 (Monday-Friday; 10 a.m.-12 noon and  1-4:30 p.m.) or send an e-mail to hortline@iastate.edu. For more gardening information visit us at Yard and Garden Online at www.yardandgarden.extension.iastate.edu


I planted some strawberries this spring. Do the blossoms have to be removed this year?

During the first growing season, all the blossoms should be removed from June-bearing strawberries. If the berries are allowed to develop, they will reduce plant growth, runner production and next year’s crop. Check the plants once a week and remove the blossoms by pinching or cutting. Flower production on June-bearing strawberries should end by early July.

With everbearing and day-neutral strawberries, remove all blossoms until early July. Any flowers which appear after this time may be allowed to develop into fruit. The first berries should ripen in August. Fruit production should continue until frost.

The strawberry planting should come into full production the year after planting.

How deep should the mulch layer be around trees and shrubs?

Mulches, such as wood chips and shredded bark, help to conserve soil moisture and control weeds. Mulches also simplify maintenance activities around trees and shrubs and reduce the risk of mechanical damage to plant materials from errant lawnmowers and string-trimmers. The optimum mulch depth depends upon the type of mulch, soil texture, plant type, and other factors. A thin layer of mulch will not effectively control weeds or conserve soil moisture. An excessively deep layer of mulch may result in water logging of heavy soils and may interfere with the movement of oxygen into the soil.

A 3- to 4-inch-layer of wood chips or shredded bark would be appropriate for well-drained sites around trees and shrubs. On heavy soils, a 2- to 3-inch-layer would be suitable. Do not pile mulch against the trunks of trees. Mulch piled up against tree trunks may create favorable conditions for fungal cankers, root rots and rodents. Keep the mulch at least 6 inches away from the trunks of trees.

When can I start harvesting my newly planted rhubarb?

After planting rhubarb, it’s usually best to wait two years (growing seasons) before harvesting any stalks. The two-year establishment period allows the plants to become healthy and vigorous.

Rhubarb can be harvested over a four-week period in its third year. Stalks can be harvested for eight to ten weeks in the fourth and succeeding years.

My bearded irises are no longer blooming well. Why?

The bearded irises may need to be divided. Bearded irises should be divided every three to five years as the plants quickly become crowded and don’t bloom well. The best time to dig, divide and transplant bearded irises is in July and August.
Lack of sunlight could be another possibility. Bearded irises bloom best in full sun. Plants in partial shade may not bloom well and should be transplanted to a sunny site.


Contacts :

Richard Jauron, Horticulture, (515) 294-1871, rjauron@iastate.edu

Jean McGuire, Communications and Marketing, (515) 294-7033, jmcguire@iastate.edu

One high resolution photo is available for use with this week's column: irises.jpg [550 kb]