Last month I did a couple of talks on gardening, including a presentation on container gardening for the Bonsall Women’s Club. I’m thankful for the invitation, partly because it prompted me to condense some of my knowledge about container gardening–and fill in a few gaps with research!

Here’s a link to my presentation. In addition, I’ll try and summarize the discussion.

Why container gardening?

There are a lot of reasons you might want to try container gardening, but most seem to boil down to two:

1. Limited space. People want to grow but don’t have a lot of space. Or, you might have space but not in an area that receives enough sunlight for vegetables to thrive. Containers solve this by allowing you to turn almost any area into a garden, as evidenced by Craig LeHoullier’s famous story of turning his concrete driveway into a garden of dozens of container-housed tomatoes. Even though I have almost 400 square feet of garden currently under management (enough for multiple households), I also have an excess of seedlings and use containers to try out new varieties when I’ve run out of bed space.
2. Design and decor. Containers and their plants add color and texture to landscapes, porches, decks and existing flower and vegetable gardens. I like to use them to add color to the garden in February, when not much is blooming (but cool-season vegetables are thriving here in Zone 10a).

What can you grow in containers?

The answer is just about everything. You just need the right container size. If you think about it, raised beds are simply containers. That said, different varieties of fruits and vegetables have different container size needs, and I tend to err on the larger size when unsure. Here’s an overview:

• Large vegetables: one plant per container. Use a minimum of 8- to 10-gallon containers with a depth of 12 to 16 inches. Examples include tomatoes, pepper, eggplant, cucumber and winter squash.
  
  Note: I attended a tomato-growing workshop led by Steve Goto (who has since sadly passed away), and he imparted some excellent tips. One was to use a minimum size of a 15-gallon container for indeterminate tomatoes, and the other was to use a wealth of good soil, compost and fertilizer. He recommended Recipe 420 garden soil for most of the container, with layers of organic fertilizer (such as Dr. Earth), worm castings, compost, and more soil. Placed in a nice sunny location with a drip system running through, I’ve had tomatoes absolutely thrive and grow vigorously up a cattle-panel arch in our cottage garden.
  
  Additional note: If you ask experts like Craig LeHoullier (who wrote Epic Tomatoes), he’ll tell you that large containers are unnecessary–that you only need a 5- to 10-gallon container, which is watered daily and fertilized weekly. I say try both approaches. Steve’s has still worked the best for me, but I wanted to give you different information I’ve gleaned.
  
• Medium vegetables or flowering plants: Use a minimum of 4- to 6-gallon containers with a depth of 8 to 12 inches. Examples include dwarf varieties of the bigger veggies (pepper, eggplant, tomato, cucumber) and brassicas like broccoli and cauliflower, beans, beets, chard, carrots, cabbage and larger herbs (rosemary, parsley, lavender and fennel). You can also plant flowering and foliage perennials and ornamental grasses.
  
  I’ve discovered a few container varieties of vegetables that I love, including Tidy Treats tomato, Tasmanian Chocolate (dwarf) tomato and Patio Baby eggplant.
  
• Small vegetables or flowering plants: Use a minimum of 1- to 3-gallon containers with a depth of 4 to 6 inches. Examples of small vegetables, herbs and flowers include basil, cilantro, thyme, mint, marjoram, scallions, spinach, salad greens, Asian greens, peas, beans and flowering annuals.
  
  In flowering annuals, I’d exclude dahlias (at least the big ones) and the larger zinnia varieties, like the Benary’s Giant series. Rarely will you find me trying to grow these–or sunflowers–in containers. Last year, I tried with the Queen Red Lime zinnias and did well with an old horse water trough (probably 55 or more gallons in size), yet not as well with a 12-gallon container.

Tips for container gardening

Here are a few things to keep in mind when using containers.

1. Be aware of the container material. For example, terracotta will dry out more quickly than wood, so you’d need to water more. Also, there are materials like railroad ties that make lovely big wood pieces but that also contain toxic resins that aren’t suitable for growing food.
2. Remember that containers dry out more quickly than when growing in-ground. The concept to keep in mind here is that the greater the surface area, the faster soil will dry. This means that if you’ve decided to buy one of those cute raised beds lifted two feet off the ground and have airflow above, on the sides and below the bed, that equates to more surface area and therefore faster drying of your soil and plant. Adjust your irrigation accordingly!
3. Soil is really important. Every inch of soil counts, so be generous on soil and fertilizer. Look for potting mixes with peat moss to absorb water and vermiculite or perlite to create air/oxygen flow and good drainage. If you’re growing succulents, make sure drainage is excellent.
4. You don’t need to put gravel at the bottom of the container to create drainage. This is a hugely debated topic, but I’ll go with Joe Lampl‘s advice and that of the author of Complete Container Herb Gardening by Sue Goetz. You do, however, need a hole at the bottom of your container for good drainage.

That covers some of the basics of container gardening. I think I’ll save the topic of designing with containers for another post. Happy container gardening!