Dear EarthTalk: I want to start an organic vegetable garden in my yard and I would like to know how to combine crops to make better use of time and space. – Val Thomason, Denton, TX

Most commercial farms concentrate on growing a few select crops to supply a wide variety of customers, but gardening at home is a different story entirely. Most backyard food gardeners are looking to augment their family’s diet with a variety of seasonal fruits, vegetables and herbs throughout the growing season.

For those of us who face time and space constraints in our gardening endeavors, combining crops within the same planting areas makes a lot of sense. Such techniques are particularly well-suited to organic gardens where chemical fertilizers and pesticides aren’t used to artificially boost crop productivity.

The most common way to combine garden crops is via an age-old technique called interplanting, which in essence means planting various garden edibles with different growth and spacing attributes together in the same soil beds or rows. One example involves combining fast-maturing vegetables, such as lettuce, field greens or beets, with slower-maturing ones like winter squash or pole beans. According to the informational “Our Garden Gang” website, mixing tall plants, like sweet corn, peas or staked tomatoes, with low-growing crops such as melons or radishes, is another way to maximize diversity and yield.

Building on the idea of interplanting, Better Homes & Gardens magazine suggests that gardeners combine plants that produce vines and can be grown on trellises or fences along with low-growing crops. So-called “vertical gardening” concentrates much more production into each square foot of planting area. Also, the magazine reports, crops grown off the ground “tend to be healthier because they are less likely to contract fungus infections or soil-borne leaf diseases.” Tomatoes, pole beans, cucumbers, snap peas, melons and winter squash are all examples of crops suitable for vertical gardening if staked or supported properly.

Another common technique often employed by “weekend” gardeners, organic or otherwise, is succession planting, which entails replacing a finished crop with a different one, or planting a single crop in small amounts over an extended period of time. One example would be to replace a spring crop with a summer crop, such as planting cucumbers-which thrive in warmer weather-where the peas had been growing earlier. Another form of succession planting involves staggering the planting of seeds from one specific crop throughout its growing season to ensure a continuing supply as long as possible.

Some crops particularly well-suited to succession planting include bush beans, lettuce, spinach and radishes, each of which have long growing seasons but can be harvested after only a few weeks. A related technique would be to plant both early- and late-maturing varieties of the same type of crop around the same time, and harvesting the resulting crops successively. Tomatoes and corn, for example, each come in varieties that ripen at different times during their respective growing seasons.

And while it may be easy to get carried away with edible gardening, don’t forget to plant a few flowers to spruce up the look of your garden and also attract bees to help pollinate your food crops. Marigolds and sunflowers are good choices as they are relatively easy to grow organically and tend to attract lots of bees.

CONTACTS: Our Garden Gang, http://ourgardengang.tripod.com; Better Homes & Gardens, www.bhg.com.

Dear EarthTalk: Are there any flea and tick products out there that don’t contain toxic chemicals?

–Ewan Locke, Madison, WI

Harmful pesticides in mainstream flea and tick products are indeed hazardous to more than insects. The active substance in most of these products is likely one of seven common organophosphate insecticides (OPs), which work by interfering with the transmission of nerve signals in the brains and nervous systems of not just insects-most of whom die on the spot-but to a lesser degree in pets and humans as well. While it would certainly take an awful lot of exposure to OPs to affect a full-grown healthy human adult, no one is sure how the chemicals might affect children or those with pre-existing nerve disorders.

The non-profit Natural Resources Defense Council (NRDC), which authored the 2000 report “Poisons on Pets” (results are online at the group’s GreenPaws.org website), reports that “studies with lab animals have raised concerns among scientists that children exposed to certain of the pesticides in pet products-even at levels believed to be safe for adults-face much higher risks, not only for acute poisoning, but also for longer-term problems with brain function and other serious disease.” The group adds that children’s behavior-notably toddlers’ hand-to-mouth tendencies and the fact that kids play where such toxins often accumulate-makes them more vulnerable to ingesting OPs than adults in the same household.

The magnitude of the potential risk to public health is what makes the inclusion of such chemicals in pet products so troubling: Surveys show that as many as 50 percent of American families report using some kind of flea and tick control product on pets, subjecting untold millions of children to toxic chemicals on a daily basis. Initial research also shows that thousands of pets may be sickened or die each year as a result of chronic low-dose exposure to OPs through their flea and tick collars.

Fortunately, several non-toxic alternatives to OP-laden flea and tick control products are now available. NRDC tested upwards of 125 pet-oriented flea and tick control products for its Poisons on Pets report and found less than two dozen that don’t contain harmful chemical compounds. Stripe-On formulations from Adams, Breakthru, Demize and Scratchex get high marks from NRDC for low-toxicity, while tabs (pills) from Comfortis, Program and Sentinel also make the safety grade. Hartz, which uses OPs in most of its product line, also offers some safer formulations (Spot-On, Advanced Care and Ultra Guard) for cats and kittens. These products rely on insect growth regulators, which arrest the growth and development of young fleas, rather than pesticides to simply kill them. NRDC notes, however, that even these safer formulations contain chemicals, and that all such products should be used with caution.

One way to treat your pet but avoid chemicals altogether is to go the essential oil route.‚  Oils from cedarwood, lemongrass, peppermint, rosemary or thyme have all been shown to be effective, when used sparingly, to keep fleas and ticks away from pets and their favorite haunts. Of course, a little conscientious legwork can obviate the need for any kind of topical or pill-based flea and tick control products, toxic or otherwise. According to NRDC, frequent washing and combing of pets and vacuuming carpets and furniture can bring mild flea infestations under control and help avoid outbreaks altogether.

CONTACT: NRDC Green Paws, www.greenpaws.org; Scratchex, www.scratchex.com; Sentinel, www.sentinelpet.com; Comfortis, www.comfortis4dogs.com; Hartz, www.hartz.com.

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