Bonsai literally means a big tree in a small pot, but in practice, it is the art of creating dwarf plants and trees in ornamental trays.

Dave Remington is — among other things — the bonsai specialist at O’Donal’s Nursery in Gorham. He creates bonsai plants that are for sale in the shop, and conducts occasional classes in the art.

“There are indoor and outdoor bonsai,” Remington said. “Evergreen and deciduous plants are used for outdoor bonsai. All of the indoor ones are tropicals.”

Remington said homeowners who run into trouble growing bonsai often leave outdoor bonsai indoors too long.

“You really shouldn’t keep them indoors longer than three days,” he said. “After that, you have to take them back outside.”

If you want to display outdoor bonsai indoors continually, you should have several plants and rotate them in and out throughout the season.

When I spoke to Remington the Friday after Thanksgiving, he had already moved his outdoor bonsai to the O’Donal’s root cellar for winter storage.

He said the plants require an extensive period of time with temperatures below 45 degrees so they go dormant. But they should not be left unprotected outdoors, because they could get damaged when temperatures fall below freezing.

“If you don’t have a root cellar, an unheated garage works fine,” he said.

Tropical bonsai can be kept inside all year long, but they don’t look their best in winter.

“Tropicals can drop two-thirds of their leaves in winter, because of the decrease in light,” Remington said. “Then they will have a flush of growth. They can drop them as many as three times during a winter. I have people bringing them in because they think they are dead.”

While the tropical plants are meant for indoor use, Remington said they will flush out and get healthier if you place them outside during the summer, as long as the temperature is above 60 degrees and they are placed in the shade after two weeks in the sun.

Remington starts his bonsai from the regular stock of plants that come into O’Donal’s, although he favors the plants in the clearance area that the O’Donal staff calls the “orphanage,” with damaged or less-than-healthy plants that will require some tender care.

“They often have an unusual shape that lends itself to bonsai,” he said, “and they are great bargains, often at $5 or $10 per plant.”

Once Remington selects a plant, he will prune out about a third of the plant’s top and a third of its roots. He stresses that you should never cut out more than a third at a time.

All of the large anchoring roots should be removed, leaving behind the smaller, thinner roots to feed the plant. To replace the anchoring roots, you have to use thick wire to anchor the plant to the tray through drainage holes in the bottom of the trays.

The roots should be pruned every two to four years, with older bonsai being pruned more often. Remington prunes by taking the plant out of the tray and snipping, often using the Felco pruners that he uses for just about everything else working with plants at the nursery.

There are some specialty tools that come in handy as well, including a pruner that cuts right next to the stem without leaving a stub. You don’t have to get a new pot every time you prune the roots; you can just put the plant back into the same pot.

It is with the top of the plant, however, where growers get to be artistic. Classic bonsai shapes make the tree look like it has been blown in the wind and otherwise weathered, but you can prune to put twists in the stems, show a lot of root, or otherwise make your plant look like an old tree growing in a bonsai tray.

The best way to tell if bonsai needs watering is to feel the soil. The soil should not be allowed to dry out. In the heat of summer. outdoor bonsai might have to be watered daily.

When they are dormant, Remington will water them about once a month. With tropical bonsai, he will use a humidity tray during winter.

Remington usually offers a couple of bonsai classes at O’Donal’s each year, usually one just before Christmas — although this year’s has not been scheduled yet — and another one in April.

O’Donal’s sells bonsai starter kits for about $50, Remington said, but the larger bonsai that I saw for sale listed at about $140. The bonsai trays go about $40 each by themselves.

Remington learned to care for bonsai mostly by reading books and experimenting. He went to work at O’Donal’s about 10 years ago after studying at the Soils and Plants program at Southern Maine Community College.

At that time, Arthur Davis had closed his bonsai business in Woolwich, so there wasn’t a bonsai specialist in the area. Remington approached O’Donal’s then-president about starting a bonsai program in addition to his other duties at the nursery. She approved the program, and the business has been going steady ever since.

Since Remington started, Colin Lewis — who used to work in Massachusetts — has opened a bonsai business in the Kennebunks. Entwood Bonsai in Burnham has been in the bonsai business since the mid-1990s.

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:

tomatwell@me.com