Extension News

Ask the ISU Experts

violet plant

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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





The top portion of my white birch failed to leaf out this spring.  What’s wrong with the tree? 

The “white birches” include the paper birch (Betula papyrifera), European white birch (Betula pendula), and Asian white birch (Betula platyphylla). They are grown chiefly for their papery white bark which exfoliates from the trunk and large branches as they mature. While attractive trees, white birches are not well adapted to growing conditions in Iowa. Birch trees have shallow root systems and prefer moist, well-drained soils. Hot, dry weather weakens the trees. The weakened trees are then attacked by the bronze birch borer. Dead branches in the upper portion of birch trees are usually the first symptom of an infestation of bronze birch borers. Trees weakened by drought and attacked by bronze birch borers usually die within a few years. 


Since bronze birch borers normally attack only weakened birch trees, home gardeners should strive to maintain healthy, vigorous trees. During hot, dry periods, thoroughly water white birch trees every 7 to 10 days. A fertilizer application in early spring also may be beneficial. 


The best birch for Iowa is the river birch (Betula nigra). The river birch tolerates hot, dry weather very well.  It is also borer resistant.  The river birch’s exfoliating bark varies from light reddish brown to dark brown. The cultivar Heritage® has salmon white bark. 


I planted several peonies last fall.  When will they begin to bloom? 

Most peony plants produce few, if any, flowers the first spring. In fact, it’s advisable to pinch off any flower buds that develop the first spring to promote root and foliar growth. Flower bud development requires a great deal of the peony plant’s energy. Initially, the young plant’s energy should be directed to root and foliar growth to aid plant establishment. Peony plants should be blooming well by the third or fourth year. 


How can I control violets in my lawn? 

Several species of violet (Viola species) are native to Iowa. Violets often grow in colonies and can be found in a wide variety of habitats ranging from dry, rocky prairies to moist woodlands.  They also adapt well to landscape sites. They are a common weed in lawns, especially in shady areas. 


Violets are low-growing, clump-forming plants. Most violets have heart-shaped leaves. They bloom in spring (April to June).  Flower colors include white, yellow, blue, and purple. A few are bi-colored.  Each flower is composed of an upper pair of petals, two side petals and one lower petal. The fruit is a small capsule which splits into three parts at maturity. 


Violets are difficult to control in turfgrass areas. Digging up the plants is an option for home gardeners with a small infestation of violets. Broadleaf herbicides are the most practical solution when dealing with large numbers of violets. Broadleaf herbicides containing triclopyr usually provide good control of violets. Applications can be made in spring or fall. Two applications, three to four weeks apart, may be necessary to achieve good control.



Contacts :

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

Jean McGuire, Continuing Education and Communication Services, (515) 294-7033, jmcguire@iastate.edu

There is one photo available for this week's column: Violet51006.jpg, [2 MB]