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WHAT’S BLOOMIN’

Gardening column: Black walnut tree can poison plants

Toxic zone’s radius could be as long as 80 feet.

Friday, May 10, 2013 - 12:01 am

Q: I've heard that a black walnut tree is toxic to tomato plants. Is that true and, if so, why?

A: Actually, black walnut trees are toxic not only to tomatoes but other plants as well. This list includes: asparagus, cabbage, pepper, potato, apple trees, blueberry, blackberry, azalea, yew, columbine, lily and petunia.

The reason for this toxicity is called juglone, a substance the tree produces in its roots, leaves, nuts and branches. The area right under the tree is the most toxic area, but anywhere near the tree, plants can still be affected. “The toxic zone from a mature tree occurs on average in a 50- to 60-foot radius from the trunk, but can be up to 80 feet.” (http://ohioline.osu.edu/hyg-fact/1000/1148.html).

If you have a black walnut tree nearby and you notice yellowing and wilting foliage of plants that I've listed above, taking early action and moving the plants may save them. Once the plant begins to show signs of toxicity, it usually dies very quickly.

If you have a black walnut on or near your property, the above link gives a list of plants that are not affected by juglone, as well as a more complete list of those that are.

Q: I would like to grow asparagus in my home garden. Can I do that and how?

A: I'm not an expert on the subject, so I'll give you what tips I know and direct you to the publication that has the answers.

•Asparagus is a very long-lived perennial that likes full sun and well-drained soil.

•Initial planting should be in warm soil. Roots will rot or can become diseased if planted in cool, wet soil.

•Buy 1-year-old, disease-free crowns from a reputable supplier.

•Plant no deeper than 5 to 6 inches. Deeper will cause yield to be less than desired.

•Pull weeds by hand and cultivate during the first year. Other methods of weed control can be used after the asparagus bed is established.

•For complete instructions on how to successfully raise asparagus, see the Purdue publication HO-96W: www.hort.pur due.edu/hort/ext/Pubs/ HO/HO_096.pdf.

Q: I purchase peat pots to start seed in, but it seems after I put pot, plant and all in a container or the garden, the plant doesn't do very well or it seems to take a long time for it to grow. Am I missing something? I thought the little pot composted right into the soil and that was the end of it.

A: Peat pots are helpful to start seed, but they need to be kept very wet to decompose — otherwise they act as a restrictive container. You need to help root growth by breaking the peat pot apart. Some plants have stronger, more aggressive roots that will push right through the peat, but other plants' roots will stay coiled around inside the pot.

When transplanting either into a larger container or the garden, make sure the peat pot is very wet, and then tear out the bottom and break the sides apart — do this gently so you do not disturb the roots — and then plant the peat pot, parts and all, along with the plant.

If you are inserting these into a hanging basket or container that allows the plants to hang upside-down, just tear away the bottom of the peat pot so the roots can have freedom to grow.

Jane Ford is an Advanced Master Gardener. Email questions to jaf701@frontier.com. You also can read her What’s Bloomin’ blog at www.news-sentinel.com. This column is the personal opinion of the writer and does not necessarily reflect the views or opinion of The News-Sentinel.