From afar, they look like hairy grapefruits floating in midair. Up close, they're your introduction to kokedama.

It means "moss ball" in Japanese, and it involves embedding plants in mud balls, covering them in moss, and suspending them from the ceiling for display. Despite the heavy sound of it, it's a lighthearted amalgam of many things - bonsai, the Japanese art of growing small trees in dishes or pots; terrariums; hanging gardens; and other forms of living sculpture.

Mostly, kokedama - pronounced ko-kee-dam'-a - is a thing unto itself.

"Adorable," says Lauren Hoderny, a senior gardener at Longwood Gardens in Kennett Square, who taught her first workshop on the technique in late March and hopes to do more in 2014.

Hoderny had never heard of what she jokingly calls "kokedoodoo" until early that month, when a colleague returned from the 2013 Philadelphia Flower Show raving about the floating plants she'd seen there.

Hoderny went online, plugged into some blogs, videos, and a handful of articles, and decided this new potless planting style was a nascent trend.

"I wouldn't really consider it bonsai, I don't know how ancient it is to put a plant in a ball or cover it with moss, and I'm not sure who decided to string it in the air," Hoderny says, "but it's really neat."

Kokedama's roots, if you will, may be Japanese, but in the last few years, the technique has been exuberantly interpreted by - and become identified with - a Dutch botanist and floral artist. He calls his creations "string gardens."

They hang alone - very dramatic - or in otherworldly clusters, inside or outside. Van der Valk works with a long and interesting list of greenery: hyacinths, geraniums, poppies, orchids, succulents, citrus plants, azaleas, asparagus, tomatoes, even small trees.

"Ours are houseplants, much more mainstream," says Peter Smith, owner of City Planter in Northern Liberties. He's considered the kokedama guru in the Philadelphia area and, given its squishy presence on the national landscape, possibly beyond.

It was Smith's "string gardens" that Hoderny's coworker saw at the 2013 Flower Show. Whether hanging from the top of the booth or placed in a dish, Smith says, they delighted visitors and sold well.

Particularly ones made with succulents or rabbit foot ferns, whose furry "feet" creep over the moss-covered balls. Plumosa or asparagus ferns were also popular.

But beware, buyers: Kokedamas are not tough enough for tough love. They dry out easily and need water every few days, as in "soaked in a bucket, sink, or bowl." If they're hanging outside, they need water every day.

"That tends to inhibit sales," Smith admits.

But maintenance is no obstacle for some.

Charlotte Hangsterfer, a social worker from Media, already has a houseplant collection and an acre's worth of outside chores that include planting containers with herbs and clearing unwanted invasive plants and replacing them with natives.

Still, when she heard about Hoderny's workshop, she was curious enough to go. Now she's a fan.

"I love that you can hang plants without the weight of a hanging basket," she says. "You can group the plantings much closer together than with hanging plants to make a screen or a grouping in a small place."

There is one thing. "The process was easy but messy," Hangsterfer says.

Hoderny's process goes like this:

She shakes the excess soil off the plant roots to make them as small as possible, then covers them with mud shaped into a sphere using one part field or garden soil, two parts potting mix, and enough water to create a moist, claylike consistency.

Hoderny makes a hole in the top of the ball with her thumb, squeezes the plant inside, and resculpts the ball. She covers it all with dried or live sheet moss, keeping everything wet so it sticks together.

Then, holding on to one end of the ball, she wraps it with twine, waxed cotton cord, or colored string "in a spider-webby kind of way."

"Make sure everything's held in there and be careful not to girdle the plant," says Hoderny, who likes to work with peperomia, goldfish plant, phalaenopsis orchids, and staghorn ferns. (She has two kokedamas at home, a purple oxalis hanging over the kitchen sink and a mini-Boston fern in a dish.)

If you started the string at the top, end there, too. This makes the kokedama a lot easier to hang. (You can also hang the plant at an angle.)

Smith's methods are similar, but his mud ball is 60 percent peat moss and 40 percent akadama or bonsai mix, a rocky, nonsoil blend that drains well. He uses live moss, which gets dunked in water two to three times a week to stay green, and he likes the mud to be one inch thick around the root mass.

Start with smaller plants only, because "the bigger ones are harder to hold together as you're doing the moss," says Smith, whose favorite "bigger ones" include alocacia, pencil cactus, maidenhair, and staghorn ferns.

Do it right, and kokedama can last up to a year. After that, you may want to make some more mud and start over.

Make Your Own

City Planter, 814 North Fourth St., will host a one-hour kokedama workshop on June 7 at 6:30 p.m.

Cost is $40, which includes plants and other supplies.

To register: Call 215-627-6269 or stop by the store.

Students will make one kokedama in class and get a take-home kit with materials needed to make a second kokedama with a plant from home.

Light refreshments will be served.