Raised beds can take a garden to the next level. Here's what to know.

One of the first lessons I learned as a gardener is that if you don't have high-quality soil, the greenest thumb in the world isn't going to save your plants. When we moved into our home half a dozen years ago, I soon realized that the dirt in our backyard was not viable for growing. Thick with clay, it was intersected by so many roots that it was impossible to push the shovel into the earth without hitting one.

I needed raised beds to fill with garden-level soil before I could sow my first season's plantings. I purchased a few kits made with untreated wood - they were cheap and easy to assemble - and packed them with a combination of bagged soil and composted kitchen scraps.

It only took me a couple of years to regret my choice. The side planks buckled, and those resting on the ground rotted away. The rich loam inside began spilling out onto the white pebble pathways around the beds, an eyesore and a waste. This spring, I ripped them out and replaced them with a trio of new raised beds and an herb garden on wheels, but first I spoke with three gardening experts and spent a lot of time researching my options.

Here are the five factors they say you should consider when choosing raised-bed kits:

- Materials. Kevin Espiritu, founder of Epic Gardening, generally recommends buying metal raised beds over those made of wood. "When you do the calculation on longevity of metal versus wood, metal beats out wood," he says. "And during the pandemic, the cost for wood has skyrocketed, so sometimes wood is even more expensive than metal." He notes that good metal beds will last more than a decade with proper care, which includes ensuring the bed doesn't flood often or consistently sit in moisture. And line it with geotextile fabric or landscape fabric if you're growing crops requiring acidic soil, which will corrode the metal.

- Size. Beds should be at least a foot tall, says Josh Singer, a community garden specialist with the D.C. Department of Parks and Recreation. "Bigger crops, such as tomatoes and squash, need at least that much room for their roots to grow," he says, adding that you can even dig up another foot of ground below the bed to give plants space to expand. To ensure that you can easily reach across the entire bed - and that it won't be so long that the sides bow out - he advises keeping beds two to four feet wide and four to eight feet long.

- Beauty. "In urban and suburban areas, you probably only have a patio or small yard, so you're probably going to want to like what you're looking at out there," says Tim Williams, operations manager of Greenstreet Gardens, a landscaping and design company. "But if pretty isn't a factor for you, don't worry about it. No one is going to judge you."

- Assembly. "It's smart to have gloves on hand," Espiritu says. "I always assemble kits using a drill with a screwdriver bit on it - set to a low torque, so you're not over-screwing the bolt or stripping it out - because it's faster. And have someone with you to help with the build. It'll just be easier." Don't forget to ensure that your bed is on even ground, because a raised bed on a slope will get unbalanced moisture distribution and may leak soil. (Have a level handy if you don't feel comfortable eyeballing it.)

- Cost. Last, but never least, consider your budget. A metal raised-bed kit can cost several hundred dollars, plus shipping fees if it's not available locally. The good news, though, is that by this time of year, many kits will be on sale or on clearance in the D.C. area. "But don't wait too long, because they will become unavailable, and it will be too late to plant most things," Williams says.

Here are four raised-bed kits the experts recommend:

- Vego Garden's 17-inch six-in-one modular metal raised bed If you've been browsing raised-bed options on Instagram, you've probably seen these eye-catching beds with rounded corners. Williams is a fan. "It's fantastic how much surface area you can get and the large soil volume for deep root systems," he says. The 10-piece kit with 17-inch-tall sides can be built into six configurations, both square and rectangular, including 2 by 2 feet and 5 by 31/2 feet. It takes about 35 minutes to put together. When attaching the panels in this kit and the others, check that the tops and bottoms are aligned; simply flip the panel if not.

- Birdies' tall modular raised bed. The OG of corrugated raised beds, Australia-based Birdies has been producing them for more than 13 years. Made of galvanized steel with an Aluzinc coating, the bed can be built into nine setups, rectangular and square, such as 40 by 24 inches and 66 by 40 inches. It's 29 inches tall, so you don't have to bend over to reach your plants, Espiritu says, "which is great for gardeners who are elderly or who have accessibility issues." Set aside about 45 minutes to build and install it.

- Olle's 17-inch 12-in-1 galvanized raised bed. The panels are made of galvanized steel and coated with Aluzinc, designed to reflect the sun and maintain a consistent soil temperature. The 12-piece kit of 17-inch-tall panels can be transformed into a dozen configurations, both rectangular and square, including 80 by 40 inches and 44 by 24 inches; it should take about 35 minutes to assemble. Singer likes this kit because of its durability and height. When it comes to filling it, he recommends a blend of 90 percent topsoil and 10 percent compost; the latter will decompose over the year. "Dump a couple of bags of compost into the bed at the start of each year to refresh the organic matter," he says. "And since the soil compacts, you really have to till it well every year."

- Forever raised beds. "If you want a bed that isn't wood but will last a long time and looks like wood, this is the way to go," Espiritu says. Designed to look like they're built with cedar planks, these beds are made from a composite of recycled wood and plastic. They are available in configurations of 3 by 3 feet or 3 by 6 feet, making them great for smaller backyard gardens. Expect it to take about 15 to 20 minutes to assemble.