Slugs and snails lack many things, such as intellect, cultural refinement, credit cards and sneakers. They also lack a protective exterior that most other biological organisms are familiar with. They are consequently conductive and very sensitive to any electrical charge or discharge that may be encountered by their slimy undersides. This is why copper tape can be so useful for protecting tender young plants that snails would otherwise devour.

Copper tape with an adhesive underside can be purchased at many nurseries and garden centers. It is most often applied to the upper edges of redwood planter boxes or the retaining walls of raised beds; it can also be wrapped around pots or other containers. Because the adhesive may not function long, some people prefer to staple or tack the tape in place if it is applied to wood.

I have no suggestions for preventing the tape from sliding off tapered clay pots except that the tape is just as functional when wrapped around the bottom of the pot as it would be closer to the top. It is preferable to wrap the tape around the bottom without gaps than for it to slide to the bottom from a wider location higher on the pot, potentially leaving gaps. Wrapping the narrowest part of the pot will also conserve tape.

I have actually never used tape but have found that bare copper wire works as well if stapled firmly to planter boxes without gaps. It is, of course, not as easily or effectively applied to clay pots as tape. Because it is so narrow, snails may "step" over wire contained within the corners between the bases of the pots and the surfaces on which the pots rest. I have found, however, that wire may be applied between the two rims of the popular Italian double-rimmed pots successfully. Although this requires considerably more wire than would be necessary for the narrow bases of the pots, the wire will not slide below the second rim if applied firmly.

Copper tape may be applied around the bases of tree trunks or large shrubs if necessary to obstruct snails. Snails are rarely a problem among trees but can damage several types of flowers, including citrus and hibiscus. The tape should be applied with slightly excessive tape on one end overlapping the other to accommodate for expansion of the trunk. Copper wire should only be used among trees if occasionally adjusted, or if it is applied in a manner that will also accommodate trunk expansion.

Aluminum foil is not a common deterrent for mollusks like snails, but I have placed small pots on small pieces of it for protection. It seems to have been successful, but I have not confirmed this with anyone else or determined if the snails were at all interested in the bromeliads that I was trying to protect. Of course, none of these deterrents would be successful if plant material contained within is in direct contact with anything outside from which slugs or snails may commute.


Flower of the Week: Sky lupine

The native annual sky lupine, Lupinus nanus, like its associate, the California poppy, is not nearly as common as it was prior to the introduction of more voracious forage grasses. It is occasionally seen in the wild and in gardens where it may have been planted from seed last winter. It is now somewhat late to sow more seed but still feasible. Lupine germinate slowly but may sprout sooner if the seed's very hard shell is first scratched on sandpaper.

Soil of inferior quality is not a problem if it is well-drained. Full sun exposure is important. Sky lupine easily naturalize if competition with other species is minimal. The palmately compound foliage is low, but the symmetrical floral spikes supporting small but profuse blue flowers may be as high as 18 inches.

Horticulturist Tony Tomeo can be contacted at 408-358-2574 or at LGHORTICULTURE@aol.com.