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The Plant Medic

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Upkeep needed for white pine

Q. In recent years my grove of white pines has really suffered. I have had several trees die, and others just don’t look healthy. Can you tell me what’s going on?

A. There could be several issues that are causing your white pines to suffer.

White pine decline is probably the root cause of your problem.

The white pine is a native conifer that was widely distributed throughout eastern North America, including northern Indiana and northeastern Ohio. It was originally confined to Appalachia, New England and southern Canada at the time of European settlement. It is the only evergreen in the eastern United States with five soft needles per bundle. An easy way to remember this is that the word white has five letters – representing the five needles.

It is a valued native tree. The inner bark or cambium was used as a food source by American Indians. The sap was used to seal baskets.

Turpenes from the tree sap are still used to make paint thinners and turpentine. The tree was marked the “King’s pine” by the English for their exclusive use for ship’s masts. The colonists would take great delight in rubbing off the marks, or cutting the trees to use for their own ship’s masts. It still remains a valuable lumber and pulp tree. It’s a top choice for a Christmas tree.

Unfortunately, urban sites in northeastern Indiana are not optimal for white pines. White pines grow best on well-drained, slightly acidic soils. They are intolerant of both severe drought and flooding.

The tree is also sensitive to extreme heat, pollution and salt spray. Think of white pines as the delicate child in a family – the one who catches colds easily, and doesn’t tolerate stress well.

Declining white pines usually develop pale green or yellowish needles. Needles often are shorter than normal and sometimes the tips of needles turn brown. Needles from the previous season often drop prematurely, giving the tree a tufted appearance. With loss of needles, the tree struggles to produce the energy it needs to survive.

Do not mistake annual needle drop for white pine decline. It is normal for conifers to drop their oldest needles in the fall.

The best way to avoid decline in white pines is to keep the trees as healthy as possible. Don’t plant white pine in wet areas. Avoid planting near heat islands of asphalt or where deicing salts are used.

Water trees during severe drought periods and make sure the trees go into the winter months well-watered. Use pelletized sulfur (1 pound per tree) around newly planted trees yearly. Use compost as mulch around young trees. Allow the pine straw to remain around older trees – this helps conserve moisture and acidify the soils.

If your urban site isn’t optimal for a white pine, consider using White or Norway spruce, or Bald cypress as substitutes. Residents can access Purdue Extension publication BP-34 (White Pine Decline) for more information.

The Plant Medic, written by Ricky Kemery, appears every other Sunday. Kemery is the extension educator for horticulture at the Allen County branch of the Purdue Extension Service. Send questions to kemeryr@purdue.edu.

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