July 2003 - Indiana Yard and Garden - Purdue Consumer Horticulture

July 2003

Q. How deep should mulch be at the base of a tree? I usually put a light coating around the trunk, in a circle, but I see some professional landscapers making big mounds. Does that keep more moisture in? — Shirley North, South Bend, Ind.

A. Generally, a layer of mulch should be 3-6 inches deep, not a volcanic pile like you see around some trees! Even at this reduced depth, it should be pulled back from the trunk to reduce moisture around the bark and limit rodent activity. In the winter, voles and field mice can tunnel right through the loose mulch to gnaw at the tree trunks. This often girdles the tree, causing eventual death.

I’m unable to explain why some landscapers put such deep mounds around each tree. Perhaps it is to discourage the people mowing from running their mowers over the mulch and displacing it. It may keep the soil more moist in that area, but since the tree roots extend well beyond most mulch rings, it doesn’t have a positive effect on the tree.

Q. I have used your advice with success concerning using Grass-B-Gone in iris beds. Can the same product be used with daffodils? If not, do you have a solution to keep the grass out of daffodil beds? — Marian McCracken, Washington, Ind.

A. The product label shows plants that are tolerant of this herbicide, and no bulbs are listed. Instead, wait until the bulbs have finished blooming. Leave the foliage in place until it yellows for maximum food production that leads directly to bigger, stronger bulbs in the ground. Garden rumors abound that it is all right to braid or knot the foliage with rubber bands. This breaks the capillaries needed for food and water transmittal and is not a good garden practice. Once the foliage begins to yellow, cut it off at the ground, allow it to die back completely so no green tissue shows at ground level, and spray the weeds with glyphosate (often sold as Round Up or Kleen Up). Glyphosate is transmitted via all green tissue to the roots so it is important that the bulb foliage is not at all green and that no surrounding desirable plants come into contact with the chemical.

Then, add a thick layer of organic mulch. It will reduce weeds and increase the health of your bulbs.

Q. During these past cold and gloomy months, we’ve enjoyed a half dozen primroses in full bloom on our kitchen windowsill. Now, they are fading, and we would like to know how to treat them so that they can be planted outdoors after the last frost date. The leaves are becoming dry and yellow despite frequent watering, but new crowns are also emerging on some of the plants. Should we be removing the faded leaves? Do we hold back on watering and sunlight to allow the plants to rest? Will they naturalize and spread in shady areas of the garden? We certainly enjoy your column in “Electric Consumer.” Thanks for all of the good advice. — David C. Norris, Kewanna, Ind.

A. It’s impossible to tell if you have a hardy primula or not, without knowing the genus. Many of the primulas sold as potted plants are not hardy and should be enjoyed while in flower, then disposed of. If you’d like to keep them for a second bloom, give them good ventilation and keep them cool and in light shade during the summer, giving them enough water to keep them moist at all times. In early fall, remove the dead and yellowed leaves, repot them and increase the amount of water given.

Since we don’t know if yours are hardy, you might try a few of them outdoors, keeping the rest inside.

Q. I have a “tomato tree” that I purchased about four years ago. It is supposed to get big clusters of pink flowers on the stem, which in turn will produce “Roma”-like fruits. I have given this plant everything possible, but it never produces. The literature that came with it said to keep it pruned to 5 feet tall, and it should produce fruit when it is 18 months old. It has beautiful large leaves (some are 15 inches across). I take it outdoors when the danger of frost is over and bring it back in front of a south window so it will get plenty of light. I give it Miracle Grow about once a month. I have given it “tomato food.” When it is inside over the winter, some of the leaves curl around the edges. Sometimes one will turn yellow and die for no apparent reason. What am I doing wrong? The literature didn’t say I had to have male and female plants. — Jackie Clemans, Wheatfield, Ind.

A. It sounds like a tomato plant too good to be true, and, indeed, it may be. Every so often, an advertisement reappears for the famed tree tomato, which turns out not to be related to the garden tomato. It’s Cyphomandra betacea, a tropical semi-woody shrub that reaches up to 10 feet, but the fruit is more tart and jelly-like than our garden tomato. There’s a great deal of information at http://www.hort.purdue.edu/newcrop/morton/tree_tomato.html, including this description of the fruit: “The fruit…flavor suggests a mild or under-ripe tomato with a faintly resinous aftertaste.”

Is your plant flowering? If it is in a windless location, so there is no stirring of the branches, pollination will be adversely affected, unless there are bees to transfer the pollen. Unpollinated flowers will drop prematurely. If there are no flowers, you may want to provide less nitrogen fertilizer. Plants with abundant available nitrogen will produce a great deal of foliage at the expense of flowering.


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