Newly planted trees need care over winter to make sure their growth isn't delayed or derailed.

Here are some questions about new trees with answers from horticulturists at Iowa State University Extension & Outreach.

To have additional questions answered, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.

Q: How long should I continue to water newly planted trees?

The roots of trees continue to grow until the ground freezes in winter. If the weather is dry, continue to water newly planted trees until the soil freezes. Small trees usually require watering for one or two growing seasons. It may be necessary to periodically water large trees for three or four years.

Q: How do I prevent rabbits from damaging newly planted trees in winter?

The most effective way is to place hardware cloth fencing around vulnerable plants. To adequately protect trees, the fencing material needs to be high enough that rabbits won’t be able to climb or reach over the fence after a heavy snow. In most cases, a fence that stands 24 to 36 inches tall should be sufficient. To prevent rabbits from crawling underneath the fencing, pin the fencing to the soil with u-shaped anchor pins.

Small trees can also be protected by placing white corrugated or spiral tree guards around their trunks. Since the weather in late fall in Iowa and Illinois is unpredictable, it’s best to have the protective materials in place by early to mid-November. After a heavy snow, check protected trees to make sure rabbits aren’t able to reach or climb over the fencing or tree guards. If necessary, remove some of the snow to keep rabbits from reaching the trees.

Q: The inner needles on several recently planted spruce trees have turned brown. What is the problem?

A: The browning of needles is due to seasonal needle loss. Deciduous trees, such as maples and lindens, drop all of their leaves in fall. Though it largely goes unnoticed, pines, spruces, firs and other evergreens lose a portion of their needles (foliage) in fall.

The needles on most evergreens are retained for two to five years. New growth (needles) is produced at the tips of branches in spring. In fall, evergreens lose a year’s worth of needles. Seasonal needle loss is uniformly distributed throughout the inner part of evergreens. It is the oldest needles which are shed. The needles turn uniformly yellow or brown and drop to the ground.

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