Plastic is often seen as evil. It is derived from petroleum, and it does not decompose. Ever since Benjamin Braddock, played by Dustin Hoffman in “The Graduate,” was advised that the key to his career was plastics, it has symbolized everything phony.

But plastic has a place in the garden, even organic gardens. It’s a question of balance – whether using the material does more good than harm.

“You have to look at what benefit you get from it,” said Eric Sideman, organic crop specialist with the Maine Organic Farmers and Gardeners Association (MOFGA).

He compared it to driving cars. We all know we should use less gasoline, but almost all of us drive – and some trips are for pleasure, not need. Sideman cited floating row cover – Reemay is the best-known brand name – as an example.

Because it keeps plants warm and prevents harmful insects from landing on them, “you reduce the amount of pesticides used,” he said, “and you can get a crop over a much longer season,” which extends consumers’ opportunities to buy local.

Two other types of plastics that increase production are high tunnels and black plastic mulch (sheets of plastic similar to the material used for trash bags), Sideman said. Black plastic mulch is used most often for sweet potatoes, onions and cucurbits, such as cucumbers, squash and melons. With sweet potatoes, the plastic keeps the soil warm and prevents the plants from sending out shoots that will root and produce more potatoes, which would prevent the original sweet potatoes from reaching marketable size.

“A lot of people use it for onions,” Sideman said. “One reason is weed management, because onions are terrible competitors with weeds. And black plastic increases biological activity under the plastic because the plastic keeps the soil moist right up to the surface.”

If you search the Internet for use of plastic in gardens, you will find people who say the plastic leeches harmful chemicals into the soil, which can then be drawn into the plants. “The research isn’t there to support that,” Sideman said.

One difference between conventional and organic gardens is that, according to the national rules that MOFGA uses to certify organic farms in Maine, these farms are required to remove plastic from the soil at the end of each growing season. Some conventional farms leave the plastic in place or even till it into the soil.

High tunnels and greenhouses are other common uses of plastics to extend the growing season – almost no one makes glass greenhouses now, because they are too expensive.

All the uses of plastic that Sideman talked about are to grow food. The use of landscape fabric in ornamental gardens – and this is from me, not Sideman – should be halted, immediately. Landscape fabric is a stronger, woven, longer-lasting version of black plastic mulch. In theory, you remove all lawn and weeds, enrich the soil with compost, cover it with landscape fabric, cut holes in the fabric where you put the plants, cover the whole thing with mulch and ignore it for the rest of your life because weeds won’t appear.

It doesn’t work.

Real gardeners want to add and move plants, and landscape fabric makes that more difficult. You have to cut a new hole in the fabric each time, not easy when it’s covered with mulch – and weeds.

Yes, I said weeds. Weed seeds sprout in the mulch where it has begun to decompose, and they push their roots through the fabric, making the weeds more difficult to remove – but not quite as hard as it is to remove the weeds that started under the fabric and pushed their way through the fabric from below.

In some spots the mulch disappears – blown off, washed away or taken by mulch-thieving gremlins just to irritate you – and instead of a garden, you look at the sheen of black plastic – which is ugly.

After about three years you have a sheet of weeds being held in place by the landscape fabric. The only way to deal with that is to remove the landscape fabric. It’s not only a long, back-breaking process, but it damages the plants you want to keep.

I am sorry to say there is no easy way to have a weed-free garden full of lovely perennials and shrubs. My best advice is weed and then mulch with three or four inches of aged wood mulch. Each spring do a quick weeding and put down another inch of mulch. Mulch does decompose.

There are other uses of plastic in the garden. Many plants come in plastic pots. Some pots can be reused, some can be returned to the place where you bought the plants for reuse; often a nonprofit group running a plant sale will take the plastic pots. If all else fails, take them to municipal recycling centers. Some nurseries offer plants grown in coconut coir (husk) or in recycled plastic.

Never buy plastic labels. My wife, Nancy, cuts up milk jugs to create ours. Or save your popsicle sticks, which means you use wood rather than plastic.

It all comes down to choice. Every time you think about buying a plastic item, think again. Is there an alternative? Does the plastic provide benefits that outweigh its drawbacks? And then if you do buy plastic, reuse the items until they fall apart and then recycle them.

Tom Atwell has been writing the Maine Gardener column since 2004. He is a freelance writer gardening in Cape Elizabeth and can be contacted at 767-2297 or at: [email protected]