Extension News

Ask the ISU Experts

Note to media editors: Got gardening questions? Contact the Hortline at (515) 294-3108 (Monday-Friday; 10 a.m. -  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


The lilacs that I planted 3 years ago haven’t bloomed yet.  Can I do anything to encourage them to flower? 

Cultivars of the common or French hybrid lilac (Syringa vulgaris) often do not bloom for several (5 or more) years after planting. The shrubs must grow and mature before they are capable of flowering. Selecting a favorable planting site and following good cultural practices during establishment will allow the lilacs to flower as quickly as possible. 


Lilacs perform best in well-drained soils in full sun. Plants should receive at least 6 hours of direct sun each day.  Lilacs planted in partial shade will not bloom well. 


Good care during the first 2 or 3 years is also important. Apply a 2- to 3-inch layer of mulch around each shrub to conserve soil moisture and control weeds. Water lilacs on a regular basis during dry weather. Also, protect the lilacs from browsing rabbits by placing wire fencing around the shrubs in fall. 


While good cultural practices will aid plant growth, some practices actually may inhibit flowering. It is generally not necessary to fertilize lilacs. However, lilacs can be lightly fertilized in early spring. Heavy fertilization may promote excessive vegetative growth and discourage flowering. 


Pruning also can affect flowering. Lilacs bloom on the previous year’s growth. The best time to prune lilacs is immediately after flowering in spring. Pruning lilacs in late summer, fall or winter may remove many of their flower buds. 


While the common lilac usually does not bloom for several years after planting, several other lilacs bloom when quite small. The dwarf Korean lilac (Syringa meyerii), ‘Miss Kim’ lilac (Syringa patula ‘Miss Kim’) and Preston lilacs (Syringa x prestoniae) often begin to bloom within 1 or 2 years of planting. 


Which blueberry varieties perform well in Iowa? 

Highbush and half-high blueberries can be successfully grown in Iowa. 


Highbush blueberries perform best in central and southern Iowa. Plants develop into 6- to 8-foot tall shrubs.  Suggested varieties for gardeners in central and southern Iowa include ‘Patriot,’ ‘Blueray,’ ‘Bluecrop,’ ‘Rubel,’ ‘Jersey’ and ‘Elliott.’ 


Half-high blueberries possess greater cold hardiness and are the best choice for gardeners in northern Iowa.  Plants are relatively small (varieties commonly grow only 2 to 3 feet tall) and produce small to medium-size berries. Suggested varieties are ‘Northblue,’ ‘Northcountry,’ ‘Northsky’ and ‘St. Cloud.’ 


Plant two or three blueberry varieties to insure adequate pollination and fruit set. 


I would like to plant some astilbes. What are their site requirements?

Astilbes perform best in moist, well-drained soils in partial shade. Plants like evenly moist soils throughout the growing season. Astilbes do not like dry sites. Their foliage will turn brown when plants don’t have adequate moisture. Water retention in soils that dry quickly can be improved by working organic matter, such as compost or peat, into the soil before planting. After planting, place a 2-inch layer of mulch around plants to conserve soil moisture. Watering probably will be necessary during prolonged dry periods. 



Contacts :

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

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