How to Grow a Hydroponic Garden

Emily Marsh, who lives in Sonoma County, Calif., always thought the best thing about gardening was the feel of soil on her fingertips. But last year she and her fiancé moved to a townhouse with an 8-by-12-foot concrete slab for a backyard. As lockdowns in California stretched into the month of May, and Ms. Marsh, 30 and a co-owner of a janitorial company, read about the surge in gardens, she felt the urge to plant her own. But her only real option was a hydroponic setup.

“I was completely against it at first,” she said, adding that it just didn’t seem like real gardening. Reluctantly, Ms. Marsh purchased a unit from Lettuce Grow, a company that sells ready-to-grow hydroponic kits. “Now it’s just my favorite thing,” she said.

As fall’s first frost strikes plants across the country, you can practically hear the collective moan of America’s gardeners: No more fresh herbs, zucchini or heirloom tomatoes until next summer.

Unless you bring your pandemic garden indoors.

Like urban chicken coops and backyard beekeeping, interest in hydroponics has surged during the pandemic. For Aerogarden, another company selling hydroponic gardens, sales jumped 384 percent in the two weeks of March, a time period that followed most state lockdowns. From April through June, sales were up 267 percent year over year.

“It has been a really amazing year for us,” said Paul Rabaut, the company’s director of marketing. A representative for Lettuce Grow said it was on track to do 10 times the sales compared with last year.

Meanwhile, D.I.Y.-ers are building hydroponic gardens out of PVC pipes and five-gallon buckets. When lockdowns began, Vicki Liston, 45, a professional voice-over actor in New Mexico, wanted to limit her trips to the grocery store and started construction on a pipe-based system. She worried about keeping a pandemic garden alive in her very arid backyard, but so far the project has been a surprising success, she said.

Compared with traditional in-ground gardening, “hydroponics grows more food in less space with less water and less time,” said Dan Lubkeman, president of the Hydroponic Society of America.

That is, if you get everything right. Hydroponics is about optimizing growing conditions: You must have the perfect amount of light and nutrition available at all times. Nail it, and plants can grow up to five times as fast as they would in soil outside, Mr. Rabaut said.

Ms. Marsh, who now has gardens indoors and out, can vouch for Mr. Rabaut’s assertion. She is constantly amazed at the vigor of her plants. “We planted three tomato seedlings, and so far we have gotten 350 tomatoes,” she said. “It’s insane,” she said.

There’s a downside, though. Soil is pretty forgiving — get overzealous with your fertilizer, and your cucumbers may suffer but the soil can buffer a fair amount of the damage. Water is much less forgiving, and the Internet doesn’t always have great advice, Mr. Lubkeman said. He recommends connecting with your nearest hydroponics specialty shop where employees are likely to be experienced growers, or buying a book on the subject.

That’s one reason many new-to-hydroponic gardeners opt to buy a plug-and-play kit: These kits tell you exactly what to add and when. If you’re feeling crafty and a little adventurous, though, you can easily build one yourself.

Here’s how to reap a lot of produce without so much as getting your hands dirty.

A hydroponic setup requires a few basic elements.

Whether you construct it yourself or buy a kit, a hydroponic garden needs the following:

• Seeds or seedlings. If you’re doing this inside, look for varieties that thrive in containers. This will ensure none of your plants get so big they take over your whole hydroponic setup.

• A reservoir for the nutrient solution, which is made up of all the macronutrients (think nitrogen and phosphorus) and micronutrients (like iron and calcium) plants need.

• A “medium.” Since you’re not using soil, you’ll need something to hold the plant’s roots in place. Many mediums also help keep roots moist between waterings. Mr. Lubkeman recommends a material called rockwool for beginners.

Decide whether to build yourself or build out of a box.

As with most hobbies, you can spend a little or a lot. Originally, Ms. Marsh wanted to go the cheap route. Setting up a medium-size D.I.Y. system with a few buckets and an aquarium pump can set you back less than $150. But Ms. Marsh worried about getting everything working correctly. Lettuce Grow’s container is made from recycled plastic, and for Ms. Marsh, that tipped the scales toward buying a premade kit, even if units start at $348 — no lights included.

Aerogarden’s smallest units, which do include grow lights, start at $99, with larger models going up to $600. Ultimately, the decision about whether to buy a kit or build your own comes down to whether you enjoy tinkering or would rather not spend a Saturday gluing PVC pipes and plastic tubing together.

It’s all about balance.

Once your set up is set up, you may see seeds sprouting within three days, though some plants take longer. By two weeks, your seedlings should start to look like real plants. Which is when Ms. Liston realized that her hydroponic experiment was not going quite right. Just a few weeks in, her plants were dying.

It turned out her tap water was too alkaline. A pH buffering solution fixed the problem. (Water testing between 6.5 and 7.0 on the pH scale is considered ideal.) A setup like AeroGarden will tell you when you need to add fertilizer or adjust the pH of your water. If you built your own operation, you’ll need to remember to add nutrients and check the pH of your water (using testing strips) weekly.

“It’s been fantastic,” Ms. Liston said, adding that once she got her light, pH and nutrient levels dialed in, “it just exploded.”

There is too much of a good thing.

If some plant nutrients are good, more seems as if it would be better, right? That’s not at all the case, Ms. Liston said. So far, she’s managed not to overfeed her plants, but too much plant food can result in dead or severely damaged plants. How often and how much you’ll need to feed depends on the type of nutrient solution you’re using. Read the directions on the bottle.

Let those lights shine.

You may be able to grow lettuce, kale or herbs in a sunny window, but as days get shorter, investing in a full-spectrum, grow light is worth the expense. These lights provide the same range of light as the sun and you’ll see much faster growth, Mr. Lubkeman said. In Ms. Liston’s case, adding a light and moving her plants next to her sunniest window resulted in a noticeable change in their productivity.

Goodbye bugs (for better or worse).

Ms. Liston’s favorite thing about growing indoors is that it’s bug free. While that means you won’t need to pluck slugs from your lettuce, you will need to take over for bees and do your own pollinating. For plants like peppers, tomatoes and cucumbers, Mr. Rabaut said some customers report getting decent pollination rates just by shaking plants gently every day or two. However, you’ll get even better results if you’re willing to play the part of the bee — using a Q-tip or small brush to sweep pollen from one blossom to another.

Keep things clean.

This is in your house, after all. While there’s no dirt involved, these setups can get a little funky. Ms. Liston does a thorough wipe down of the PVC plant holders every two weeks. If you buy a premade kit, follow the manufacturer’s instructions on cleaning.

Maintenance is key.

Ms. Marsh tries to clip back greens and herbs at least two times a week. Many items — like basil — do need to be kept trimmed back or else they’ll go to seed and stop producing. While hydroponic gardens are significantly less work than their outdoor counterparts (no weeding!) you can’t neglect your plants completely and still expect them to thrive, Mr. Lubkeman said.