This year has given me a newfound appreciation for our outdoor spaces, and because I’m sure many others feel the same way, we decided to team up with Seattle’s Swansons Nursery to build a project that will help you make the most of your space—and grow some yummy produce to boot. 

This isn’t just a project for people with backyards. We’re building two different sized containers—18-by-18-inch and 24-by-18-inch—that can fit almost any space. These portable containers for edible plants can transform the look of your patio or balcony, and they’re a low-barrier way to begin gardening. 

As experts on lumber, we can tell you how to build the planters. But as for filling them with edible plants—we’ll defer to the expert Aimée Damman, marketing director at Swansons Nursery and the editor of Digging Deeper: a NW Gardening Blog. Take it away, Aimée!

I think it’s wonderful to watch something grow, take care of it, watch it mature, and then get to eat it. Just caring for something—tending to something living and green—makes us feel better and a little bit more in control. I think that’s part of the reason people flocked to gardening at the beginning of the COVID-19 pandemic. 

If you’re just starting to develop your green thumb, containers are great because you already know the size of your space—and that makes it almost like you have step-by-step instructions. It’s so much easier to get started. If you’re an experienced gardener, you know picky edible plants like tomatoes and peppers love lots of sun, and these containers are portable! You can move them around to get the most sun possible. 

Note: We recommend putting the containers on wheeled stands if you plan on moving them around—they can get very heavy when filled with soil (especially the larger one)!

Below, we’ll show you how to get your edible garden started. 

Step 1: Fill your portable container with soil

For any container planting, you’re going to use potting soil. Don’t just grab soil from your yard—it’s too heavy, likely has a lot of clay or rock, and can contain bugs and disease spores. There are a few potting mixes out there specifically for veggies, but we find a regular, quality potting mix is just fine for an edible garden, especially if you also use a natural fertilizer. And don’t use compost alone to fill a container you’re planting in—some edible plants may like the soil that rich, but not all plants do. 

Next, choose a fertilizer. At Swansons, we like a natural vegetable and herb fertilizer that you sprinkle on top of the soil, then mix in. We like both Dr. Earth and Espoma brands. You can also get a fertilizer specifically for acid-loving plants if you’re planning to grow blueberries. 

Follow the directions on the fertilizer bag for how much to use per cubic foot and mix it in as you’re planting. You’ll want to add fertilizer every three to six weeks throughout the season because nutrients run through a container more quickly than they do in the ground. 

You should fill your containers as full as possible, about ¼ - ½” from the top. The potting soil will settle as it’s watered, and the plant’s roots need as much space to grow as possible.

swansons nursery

planter box and soil

planter box soil

soil for planter box

potting mix planter box

berry tone organic

Step 2: Choose your edible plants

Before you choose what to plant, ask yourself the following questions:

  • Where will you place your containers? How much sun do you have? Are there trees or other tall buildings that will block light? What direction are you facing? Track the light throughout the day in the space you’re planning to put the containers. 
  • For areas with mostly morning sun, stick to leafy greens like kale and lettuce or herbs such as parsley, mint, and cilantro. If you’re looking to plant squash, tomatoes, or peppers, you’ll need at least six to eight hours of sunlight per day, so you’ll need a spot that’s sunny through the afternoon—or the dedication to move the containers around each day to receive optimal light.  
  • How much time do you have to devote to your edible garden? Most edible plants need to stay fairly moist and require watering once to twice daily in the heat of summer. Exceptions are Mediterranean herbs such as rosemary, thyme, and basil.
  • Most importantly–what will you plant? What kinds of food do you like? Do you want something ornamental as well as edible? Some blueberry bushes have beautiful fall colors, and herbs like rosemary stay green all year long.

Next, you’ll want to consider the size of your container. Kirsten showed you how to make both an 18-by-18-inch and 24-by-18-inch planter box. For the 18-by-18-inch, it’s best to choose one larger plant because it will grow to take up all that space—think one squash or tomato plant. Or, pick a few smaller plants like herbs and leafy greens and pair them with a flower to attract pollinators. 

Potatoes are a fun crop to grow on their own in the 18-by-18-inch container. And although you can plant potatoes from the grocery store, we don’t recommend it unless you know they are organic and know what variety they are. We recommend purchasing spuds from the garden store, then planting them between March and April. Fill the container with about eight inches of soil, then place one to three spuds and cover them with a little bit of dirt. When you see green sprouts poking out, cover them with another little bit of dirt. Do this until you reach the top of the container, then leave the plants to grow into big, bushy foliage. After flowering, when the leaves start to turn yellow and die, dig around or dump the entire container out to harvest your potatoes!

In the 24-by-18-inch planter, you have a little more room to play around. Feel free to mix and match veggies and herbs according to your taste, making sure they’re spaced out per the directions on your seed packets or the tag that comes with your plant starts. Get creative here! You could plant parsley, basil, and scallions with peppers to make a pizza or salsa garden. Or mix lettuce in with carrots and radishes for a salad bar garden.

We planted ranunculus in our blueberry box so we could have early spring flowers, and we’ll swap these out with marigolds in late spring so there are blooms all summer and into fall!

For inspiration, we've put together a few examples of routes you could take in your own boxes below (you can also download a printable version):

salad bar garden

pizza or salsa garden

single fruit or vegetable

edible plants for planter box

planter box items

flowers for planter box

planter box plants

water your planter box

Step 3: Water and watch your edible garden thrive

When you’re gardening in a container, it’s best to water slowly and deeply with less frequency, rather than dumping a small amount of water in the pot every other day. Water the garden slowly until it’s seeping out the drainage holes. Make sure your container is on risers so the water has a place to drain. Let the first inch or two of dirt dry out completely before you water again. Watering slowly and deeply in this manner allows the moisture to reach the roots, rather than only moisten the top of the soil. 

The exception is when sowing seeds and watering tiny plant babies. After sowing seeds, keep the surface of the soil lightly moist at all times—if seeds dry out they won’t germinate. You don’t need to soak all of the soil yet because there are minimal roots until the plants begin to grow a bit larger. Once the plants are up and growing, begin soaking the soil as detailed above.

diy planter box

Step 4: Harvest your hard work 

You can plant your larger container in a way that allows you to harvest annual vegetables all season long. For example, you could plant quick-growing veggies like radishes in early spring, then harvest them right around the time you plant a pepper in May. 

Veggies like lettuce can also be a good shorter-term option because they grow so quickly. To harvest lettuce, cut the plant about an inch above the bottom, and it will regrow on its own over and over. When you’re finished and want to plant something else, simply pull it out and eat it. You can then plant something else in its place.

When you take that first bite out of a freshly-picked radish or tomato, you’ll discover another gardening benefit: flavor! If you’ve ever grown your own strawberries or green beans, you know they just taste so much better than what you can get at the store. 

Whether you’re just getting started or you’re an experienced gardener, these edible container gardens can help you make the most of your outdoor space—whether that’s a backyard with spotty sun or an apartment patio.

how to garden in planter boxes

For other garden projects, check out this DIY garden trellis, a cocktail herb garden how-to, and a guide to growing vegetables in the Pacific Northwest.