So you've finally plunged your fork into the compost and planted a garden. You've discovered the delicious satisfaction of growing your own produce and now, you couldn't imagine a summer without dirt-fresh tomatoes and squash pulled from your own soil.

Now that you're thoroughly hooked on your kitchen garden, you may be feeling the itch to advance it to a new level. And one of the next logical steps is growing your own starts from seed.

If you're going to sow inside, March is the right time to get your summer crop going so they'll be ready to put in the ground by May — things like onions, lettuce, brassicas, chard, leeks, parsley, tomatoes, peppers and eggplant.

While you could find space in the garage for tables, heating pads and grow lights, you could also just bypass the baby steps and advance right to the big stuff — a cold frame or small greenhouse of your own.

Cheap to buy

These glass houses that deliver passive solar heat may seem like equipment reserved for professional growers, landowners with acreage or well-heeled hobbyists.

But cold frames, small moveable boxes with solid sides and a glass or clear plastic opening for ventilation, are cheap to buy and easy to build and can work for even condo and apartment dwellers.

Even greenhouses are available now for every budget, every space, however small, and every skill level.

At one extreme is IKEA's Sokker Mini-Greenhouse, a steel-framed glass box that is cute as a button and appealing to design geeks. But at only 17 inches long and 13 inches high, it is little more than a toy.

There are, however, many functional yet compact and easy-to-assemble seedhouses and cold frames that are small enough even to fit on a deck, where seeds can be started for container vegetable gardens.

"Industry-wide, we're definitely seeing a growth in greenhouses, and it just continues to grow," said Ed Casey, a lawn and garden buyer for Freidman's Home Improvement.

Salvaged materials

The most ambitious gardeners and urban homesteaders are building their own greenhouses using salvaged materials.

Two years ago, Paul and Suzanne Mackey of Petaluma decided they had outgrown their cold frames. So Suzanne, who writes the blog Petalumaurbanhomestead.com, asked her firefighter husband, Paul, to build her a greenhouse.

"It's really simple, carpentry-wise," said Paul. "The biggest trick is sourcing the right materials. You can always buy new-built, but our goal was to use as many recycled materials as possible."

Since a greenhouse is primarily glass or clear or opaque plastic, you'll want to look for salvaged windows.

The Mackeys found a perfect set of nine, 6-foot aluminum windows from Garbage Reincarnation at the county landfill on Mecham Road in Petaluma. Finding a whole set saved them from having to patch together a hodge-podge of different-sized windows.

He used recycled redwood from an old water tank, stored in a barn for 50 years and sourced from Sonoma Compost.

He kept the frame as simple as possible to fit the windows. He found some leftover pressure-treated wood for the foundation. He also found recycled hinges, and appealing details like a Victorian doorknob and a stained-glass window.

Beautiful colors

Suzanne said on a wintry day while sowing seeds in her warm and light-filled space, the beautiful colors of the redwood and glass brought tears to her eyes.

"A greenhouse gave me a bigger capacity and more controlled environment," she said.

A self-opening vent called a Univent on the roof opens automatically to cool the house down if it gets too hot.

The whole project cost little more than $400. But for those less confident with a hammer, there are assemble-yourself kits available at home improvement stores.

Michele Thurman, who oversees the garden and nursery department at Friedman's Sonoma store, said her stock starts with a four-tiered aluminum frame and plastic greenhouse that requires no tools ($48.85) and is very easy to assemble. It's 5-feet, 3-inches tall so you could enter it if you duck.

But there are larger kits that are 6-feet tall, enough height for most people to work within and that assemble like a pop-up canopy ($219).

More elaborate, said Thurman, is a 6-by-6-by-6-foot kit by Harmony Greenhouses with panel siding and virtually unbreakable polycarbonate panel windows ($599).

You can reach Staff Writer Meg McConahey at meg.mcconahey@pressedemocrat.com or 521-5204.