Extension News

Ask the ISU Extension Garden Experts: Fruit Trees, Begonias and Raspberries

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.


Our area experienced temperatures in the -20 to -25 degree range in January. What effects will the cold temperatures have on my fruit trees?

The cold temperatures may have damaged peach and sweet cherry trees. Peach trees are not reliably winter hardy in most parts of Iowa. Temperatures below -18 degrees Fahrenheit will destroy the flower buds on peach trees. Temperatures of -25 degrees or below may damage or destroy the peach trees themselves. The flower buds on sweet cherries are slightly more cold hardy than those on peaches. The flower buds on some sweet cherry varieties can survive temperatures of -20 to -25 degrees Fahrenheit. Iowa gardeners should expect poor crops on peaches and sweet cherries this summer. It is also possible that the trees themselves may have been damaged. Damage may vary from dieback of twigs and branches to complete death. On a brighter note, the cold January temperatures should not have damaged the flower buds on apples, pears, and sour (tart) cherries.

When should I start tuberous begonia seeds indoors?

Tuberous begonia seeds should be started indoors 16 to 18 weeks before the intended outdoor planting date. Varieties available from seed include those in the Non-Stop, Pin-Up, Panorama, and Illumination series. Tuberous begonia seeds are quite small. For ease of sowing, pelletted seeds are available. After the seeds have been sown, the germination medium should be kept at a temperature of 75 to 80 degreesF. Germination should occur in two to four weeks. After germination, place the seedlings under fluorescent lights in a cool (60 to 65 degrees F) location. The seedlings should receive 12 hours of light daily.

What are the proper pruning procedures for purple raspberries?

Proper pruning of purple raspberries promotes high yields, helps control diseases, and facilitates harvesting and other maintenance chores.

In March or early April, remove all small, weak canes, leaving only four or five of the largest, most vigorous canes per clump or plant. Cut back the lateral (side) branches to 18 inches in length.

In summer, pinch out or cut off the tips of the new shoots (canes) when they reach a height of 36 to 48 inches. Remove approximately 3 to 4 inches of the shoot tips. Since all new shoots will not reach the desired height at the same time, pinching will need to be done about once a week between late May and late July.

Finally, remove the old fruiting canes at the soil surface after the last harvest. The pruned material should be removed from the garden area and destroyed.


Contacts :

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

Del Marks, Extension Communications, (515) 294-9807, delmarks@iastate.edu