Extension News

Ask the ISU Expert


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


When is the best time to apply a broadleaf herbicide to the lawn? 

Fall (late September to early November) is the best time to control dandelions and most other perennial broadleaf weeds. During fall, perennial weeds move carbohydrates down to their root systems. If a broadleaf herbicide is applied at this time, the herbicide will be absorbed by the weed’s foliage and moved to its roots along with the carbohydrates. This results in excellent broadleaf weed control. The most commonly used broadleaf herbicides include 2,4-D, MCPP, dicamba and triclopyr. Most broadleaf herbicide products available at garden centers contain a mixture of two or three of these compounds. Broadleaf herbicides can be applied as liquids or granules. Before applying any pesticide, carefully read and follow label directions. 


My crabapple has been losing leaves since early summer.  Why? 

Apple scab is the likely cause of the premature leaf drop.  Apple scab develops on susceptible crabapple varieties during rainy spring weather. Scab appears on the leaves as roughly circular, velvety, olive-green spots on both the upper and lower leaf surfaces. The spots eventually turn dark green to brown. The spot margins are feathery rather than distinct. Heavily infected leaves may curl up, turn yellow, and fall off.  Highly susceptible crabapple varieties may lose most of their foliage by late summer. The premature leaf drop weakens the tree somewhat, but does not kill it. The damage is mainly aesthetic. Heavily defoliated crabapples are simply not attractive. 


Apple scab can be controlled by raking and destroying the leaves as they fall, pruning the tree to improve air circulation, and applying fungicides from bud break to about mid-June. However, the best way to control apple scab is to plant scab-resistant crabapple varieties. When selecting crabapples, gardeners should avoid varieties that are highly susceptible to apple scab.  Highly susceptible crabapple varieties include ‘Hopa,’ ‘Radiant,’ ‘Royalty,’ and ‘Spring Snow.’  Crabapple varieties possessing good to excellent resistance to apple scab include ‘Adams’ (deep pink), ‘Adirondack’ (white), ‘Donald Wyman’ (white), ‘Prairifire’ (reddish purple ), ‘Profusion’ (pinkish purple), ‘Red Jewel’ (white), and ‘Sugar Tyme’ (white).  The flower color of each variety is enclosed in parentheses. 


Is it possible to pick green tomatoes before the first frost and ripen them indoors?

Yes, green tomatoes can be ripened indoors. Just before the first frost, remove all mature, greenish white fruit from the vines. They should be solid, firm and free of defects. Remove the stems, then clean and dry the fruit. Individually wrap each tomato in a piece of newspaper. Store wrapped tomatoes in a cool (60 to 65F), dark location, such as a basement or cellar. The wrapped fruit can be placed in a single layer in a box or on a table. Inspect the tomatoes frequently and discard any damaged or decaying fruit. When the tomatoes begin to color, remove the newspaper and place them at room temperature. An alternate method is to leave the green fruit on the vine and pull up the entire plant. Hang the tomato plant upside down in a cool, dark location. Pick the fruit as they ripen. 



Contacts :

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

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

A high-resolution version of the above photo suitable for printing also is available:   MedCUDandelion92105.jpg [930K]