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Diagnostic Tidbits (Week of July 9) - Jul 17, 2012

by UW Extension Plant Health Clinic Team

Listed below are this week’s plant diagnostic and growing tips from the Plant Health Clinic team.

Question: How long should I water my trees?

Answer: It takes .6 gallons water for each square foot area to equal the ideal one inch per week of water plants in our area require to thrive.  This figure would be 1.5”- 1.75” in sandy soils.

Dr. Laura Jull, UW specialist, suggests a slow soaking rate of 30 seconds per gallon. A tree’s area to water is typically determined by the drip line of its canopy (more area being added if the shape of the tree is taller than it is wide). A ’typical’ tree might have an area of 100 sq. ft.  This tree requires 60 gallons of water.  At a rate of 30 seconds per gallon flow rate it would take 30 minutes to water this tree. Hopefully this example will help give you a ‘feel’ for how much to water and those of you more mathematically inclined a formula.

Question: I've been told that my 20 year old maple tree that is dying at the top has girdling root. What is it and how do I get rid of it?

Answer: This is a common problem that we see in many trees in the 10-25 age range. A girdling root is defined as "a root that grows around another root or stem," thus tending to strangle the plant. It prevents food, water, and oxygen from being transported to all parts of the tree. It is caused by improper planting of the tree. Urban trees that were planted balled and burlapped are most susceptible to girdling roots.

Signs to look for are the trunk being flattened at the soil line or if the trunk looks like a telephone pole due to the lack of a root flare. A flare is the area where the roots grow out from the tree and into the ground. The tree may turn color early, thin out ( you can "see through" the tree), show lighter colored leaves or leaves that are smaller than normal, sparse foliage. Late stages are the dying of the branches at the top center of the tree. Once the latter stages are reached little can be done to save the tree. If recognized early, removal of the circling root may save the tree. This should be done by a certified arborist. A list of certified arborists is available through the Brown County Extension office or web site at www.BrownCountyExtension.org, click on 'Urban Horticulture Resources'.

Question: I have small holes in the middle of my hosta leaves.

Answer: This could be earwigs.  This somewhat maligned bug has forcep-like pincers located on the abdomen.  They feed at night on aphids, mites, fleas, insect eggs as well as marigolds, lettuce and your hostas.  They feed mostly on dead plant and animal debris but will feed on tender petals and leaves.

Question: I want to make my lawn more ‘sustainable’.  Where would you suggest I start?

Answer:  The UW- Extension has a wonderful, frank and insightful publication:  Organic and reduced-risk lawn care.  It can be found on the learningstore.uwex.edu website by searching with code A3958.

Sustainable lawn care as a goal may be expanded to include less ‘lawn’ and more native trees, shrubs and non-woody plants.  Resources include: Rain Gardens code GWQ037, Landscape Plants that Attract Birds G1609 UWEX, Wisconsin Native Plant Sources & Restoration Consultants – a DNR publication available on line, and Wild Ones- native plants, natural landscape which is a national educational membership organization with local chapters.

If you’re bugged by garden pests or would like some free gardening advice, get your horticultural questions answered by the UW Extension Plant Health Clinic team located in the lower level of the Visitor Center and at the Brown County UW Extension office. Check out our website for Plant Health Clinic hours and contact information.

UW Extension Plant Clinic Staff members – Vijai Pandian, John Hermanson, Lynn Clark, Dan Mitchel, Sue Roulette, Vicki Warden, Ritalyn Arps and Ryan Sievert

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