UC Master Gardeners of Monterey & Santa Cruz Counties
University of California
UC Master Gardeners of Monterey & Santa Cruz Counties

Container Gardens

If you've been wanting to start a garden but feel a little overwhelmed by the task, why not a container garden? You can start simply with just a pot or two and expand as you build your confidence. Why a container garden? 

  • You can grow a great variety of vegetables, fruits and flowers in containers 
  • You don't have to do nearly as much soil prep as you do for an in-ground garden
  • Containers can be squeezed into small spaces where a larger garden won't work, for example, on a balcony or small porch.

Container Types

Container garden photo by Dan Randow. Link to license at end of article.
There are many different types of containers available to use: half wine barrels, plastic pots, glazed clay pots, 5 gallon buckets or other recycled containers can all work. I've got a container garden on my back porch with all of the aforementioned container types as well as a few others including a stock tank I drilled holes in the bottom of, some hypertufa pots, and a couple of containers I built out of old redwood deck boards. In general you want a pot that will hold soil and moisture but also allow drainage. If your container doesn't have drainage holes, make sure you add some. If your pot is large, put it where you want it before filling it with soil as it will get heavy. If your pot is less than about 10” diameter x 10” deep, be careful what you plant in it as the soil will dry out faster. That size would work for a succulent or cactus but wouldn't be ideal for a tomato plant.

Location, Location, Location

Choose your garden container location based on the cultural needs of the plant you plan to put in the container. Most vegetables need 6-8 hours of sunlight a day, as do a lot of annual and perennial flowers. Some varieties of flowers and foliage don't need as much sun or prefer it to be filtered through trees. If you aren't certain, read about the plant's needs before you choose the location.

Soil

Container garden photo by Kristine Paulus. Link to license at end of article.
Soil is probably the most important factor in having happy container plants. You want a mix that is light, easily wettable and quick draining. The soil should retain moisture but also have plenty of air spaces for the roots. About half the soil mix should be organic material such a coconut coir, compost or worm castings. The other half of the soil mix should be inorganic material such as perlite, vermiculite, or sand. A good quality soil mix might cost you a little more but your plants will be much happier and more productive. The four functions of soil for plants include:

  • Anchorage and support
  • Storage and supply of water
  • Supply of air
  • Storage and supply of nutrients

Drainage

Make sure the pot will not damage anything when water drains out of it. It's better not to use a saucer if you don't need it. Why? Because irrigation water with fertilizer in it will leave soluble salts in the soil. If you don't leech these salts out of the pot by adding enough irrigation water so some water drips from the bottom of the pot, the salts will build up in the soil and could cause problems for your plants.

Saturation Zone

There's always a saturated zone at the bottom of the pot after the water drains out. The height of the saturation zone depends on particle size. The finer the particles in the soil, the more saturation occurs. That's important because if the soil is too saturated the plant will have difficulty taking up air through the roots. And although it seems hard to believe, adding gravel at the bottom of the pot only shifts the saturated zone up, leaving less unsaturated soil for the plant to grow in. So don't put a lot of gravel in the bottom of your pots, just a few broken shards to keep your potting mix from falling out the holes in the bottom of your pot. If you have poorly draining soil in your pots, here are a few solutions:

  • Improve soil by changing it to a coarser mix
  • Practice over-potting if necessary (use a larger pot than you need)
  • Increase plant spacing to increase evapotranspiration (the water loss occurring from processes of evaporation and transpiration. Evaporation is when the water on the soil or the plant surfaces turns to water vapor. Transpiration is the loss of water through the leaves of the plant.)
  • Irrigate at mid-morning when evapotranspiration is high
Effect of gravel added for drainage. Image taken from UCMGMSCC continuing education seminar.

Nutrients

The rule for fertilizer is weakly, weekly. That is, frequent but low doses of fertilizer are best for container plants. Using a water-soluble fertilzer is an easy way to control the amount of fertilizer your plants get, because you can apply it when you water your plants, dissolved into your irrigation water. 

Visit here and here for additional reading. Don't forget to subscribe to our blog so that you receive an email notification when a new post goes up. If you have questions, contact us online, by phone or in person to get answers to your gardening quandaries!

Dan Randow's container garden photo license is here. Kristine Paulus' container garden photo license is here.

Posted on Monday, August 28, 2017 at 9:00 AM

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