Thorny or prickly shrubs make a barrier beneath windows to discourage

Q. Some time ago I saw a television show that told about the kind of bushes to plant under windows to discourage intruders. Do you know the best type of shrubs to do this? They will be planted in Michigan, about 30 miles from the Ohio border. - Marvin Williams, via e-mail

A. Shrubs with thorns can provide excellent security for your home or business, says Tim Wood of Spring Meadow Nursery in Grand Haven, Mich.

"Barberry is the most commonly available thorny shrub," he adds. "Most make excellent barrier plants as long as you choose one with the proper height."

Emerald Carousel barberry has very large thorns, green leaves, bright yellow flowers, and good red fall color. It is hardy in Zones 3 to 7.

William Penn is a semievergreen variety that has glossy green leaves that turn bronze in the autumn and nasty thorns that would deter a burglar. This selection is best for areas where winter temperatures do not go below minus 10 degrees F.

Red-leaf Japanese barberry (Berberis thunbergii var. atropurpurea) is the most commonly available barberry. It has attractive red leaves and numerous smaller thorns. The best large selection is called Rose Glow. It has slightly pink variegation on the new growth and bright pink fall color.

Five-leaf aralia (Acanthopanax sieboldianus Varigeatus) is a rugged plant that has prickles as well as attractive yellow and green variegated leaves. It grows 8 to10 feet tall and is hardy in Zones 4 to 8.

Pyracantha is an excellent choice for warmer parts of the country. This evergreen or semievergreen (depending on climate) shrub is noted for its white flowers and colorful berries in late summer, but has thorns, too.

No one will get through Rosa rugosa and if they try, they will regret it, he says. This salt-tolerant rose produces fragrant blooms and large, attractive red rose hips. Mr. Woods' favorite rugosa is Frau Dagmar Hastrup, which grows 3 to 4 feet, but for security purposes he recommends a taller variety.

For rough neighborhoods, consider Washington hawthorn (Crataegus phaenopyrum), downy hawthorn (Crataegus mollis), or Lavalle hawthorn (Crataegus crusgalli). These are shrubby trees with big thorns. Don't grow these where a pedestrian or lawn-care worker might come into contact with them.

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