Extension News

Ask the ISU Extension Garden Experts: Cucumbers, Iris, Tomatoes and Lawn Care

tomato plant

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 send an e-mail to hortline@iastate.edu. For more gardening information, visit us at Yard and Garden Online, http://www.yardandgarden.extension.iastate.edu.


Do I need to isolate cucumbers from other vine crops to prevent cross-pollination? 
Cucumbers will not cross-pollinate with squashes, pumpkins, muskmelon, or watermelons. Cucumber varieties may cross with one another. However, the quality of this year’s crop is not affected. An exception is the cross-pollination of parthenocarpic cucumber varieties with standard cucumber varieties.  Parthenocarpic varieties develop fruit without pollination. As a result, the non-fertilized fruit do not contain seeds. Parthenocarpic cucumber varieties must be isolated from standard cucumber varieties to prevent cross-pollination and seed development. 

Are there any irises that can be grown in shade? 
Most iris species (bearded, Siberian, Japanese, etc.) perform best when grown in partial to full sun. However, the crested iris (Iris cristata) prefers partial shade. A native of the eastern United States, crested iris produces four- to six-inch-long leaves from woody, spindle-shaped rhizomes. Flowers are pale blue to violet with white or yellow crests on their falls. Plants bloom in mid-spring. It is hardy in USDA Hardiness Zones 3 to 8. Because of its small size, crested iris should be grown in the front of perennial beds and borders. It also can be grown as a groundcover in partial shade. 

When is the best time to apply a broadleaf herbicide to the lawn to control dandelions and other broadleaf weeds? 
Fall (mid-September through October) is the best time to control perennial broadleaf weeds in the lawn with broadleaf herbicides. In fall, perennial broadleaf weeds are transporting food (carbohydrates) from their foliage to their roots in preparation for winter. Broadleaf herbicides applied in fall will be absorbed by the broadleaf weed’s foliage and transported to the roots along with the carbohydrates, resulting in the destruction of the broadleaf weeds. Spring applications are generally less effective than fall applications. 

What is the proper spacing when planting tomatoes in the garden? 
Tomato varieties are classified as determinate or indeterminate. Determinate tomatoes are small, compact plants. They grow to a certain height, stop, then flower and set all their fruit within a short period of time. The harvest period for determinate tomatoes is generally short, making them good choices for canning. Indeterminate tomatoes continue to grow, flower and set fruit until killed by the first frost in the fall. Accordingly, the harvest from indeterminate varieties often extends over a two or three month period. 

Spacing of tomato plants depends on the growth habit of the variety and training system employed.  Indeterminate varieties that are staked can be planted 1½ to two feet apart in the row. Indeterminate plants grown in wire cages should be spaced 2½ to three feet apart, while a three- to four-foot spacing would be appropriate for indeterminate tomatoes allowed to sprawl over the ground. Determinate tomatoes can be planted two feet apart. Rows should be spaced about four feet apart.


Contacts :

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

Willy Klein, Extension Communications and External Relations, 515-294-0662, wklein@iastate.edu

 high resolution photo tomato plant