Extension News

Ask the ISU Extension Garden Experts: Planting Trees, Blooming Rhubarb and Spraying Apple Trees

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.


How large of a hole should be dug when planting a tree?
When planting balled and burlapped and container-grown trees in well-drained soils, dig a hole that is two to three times wider than the diameter of the tree’s rootball. The depth of the hole should be two or 3 inches less than the height of the rootball. Slope the sides of the hole so the top of the hole is several inches wider than the bottom.

Poorly drained sites are difficult locations for many trees. When planting in poorly drained soils, the width of the hole should be two to three times the diameter of the tree’s rootball. The depth of the planting hole should be approximately two-thirds the height of the rootball. When placed in the hole, the top one-third of the rootball should be above the surrounding soil. When backfilling, place soil to the top of the rootball and gradually slope it down to the surrounding soil line.

My rhubarb plants are blooming. What should I do?
The flower stalks should be promptly pulled and discarded. Plant vigor and next year’s production will be reduced if the plants are allowed to flower and set seed.

Flower formation may have been induced by stressful growing conditions, such as drought, extreme heat or infertile soils. Age also may be a factor. Old plants tend to flower more than young ones. Flower formation can be discouraged by following good cultural practices. Sprinkle ½ cup of an all-purpose garden fertilizer, such as 10-10-10, around each plant in early spring. Stop harvesting rhubarb in mid-June. Water rhubarb plants once a week during prolonged dry periods. Dig and divide large, old rhubarb plants in early spring or late summer.

When should I spray my apple trees?
The main objective in spraying apple trees is to prevent insect damage to the fruit. The most important period to spray apple trees is from petal drop until just prior to harvest. Several applications will need to be made during this period. A home-orchard-type spray (available at most garden centers) is the best product for home gardeners. Most home-orchard-type sprays contain two insecticides and one fungicide and can be applied to apple, pear and most other fruit trees. See the product label for specific directions.


Contacts :

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

Christopher Weishaar, Extension Communications and External Relations, 515-294-1327, cweishaa@iastate.edu