The Coastal Gardener: Potted plant secrets, from the ground up

April 29, 2011|By Ron Vanderhoff
  • Since soil in pots decomposes it is a good idea to occasionally unpot them, remove some of the marginal soil and replace it with fresh soil. This collection of succulents is growing in Santa Barbara.
Since soil in pots decomposes it is a good idea to occasionally… (Courtesy Ron Vanderhoff )

Growing plants in containers has never been more popular. It couldn't be easier, right?

Just put some pebbles in the bottom of the pot, pour in the potting soil, add the plants and you're done, right? Well, that's not exactly how expert gardeners go about it.

Here are a few tips that I and many others practice when dealing with potted plants in their own gardens. Perhaps these techniques will help you be an even better gardener:


Drainage, Drainage, Drainage

If you read two sentences into any plant caresheet, review the cultural information in a reference book or get advice from any expert, the word "drainage" will surely come up. Good drainage simply means that water should move through the soil, from top to bottom and out of the root zone quickly.

It doesn't have anything to do with how often to water, just what should happen to the water once it hits the soil. Tropical plants, succulents, citrus, native plants, camellias and the huge majority of other plants, thirsty or not, want good drainage.


I've potted thousands of plants, and one thing I always add to my potting soil is extra pumice. I purchase pumice every time I purchase my potting soil. Looking out the window, right now I have three 2-cubic-foot bags of potting soil stacked outside, along with three 1-cubic-foot bags of pumice.

That's about the right ratio. When potting almost any plant I blend about one part of the white, rocky, pumice to three parts potting soil. I'll add even more pumice to plants that want especially good drainage; plants like natives, most succulents, potted bulbs and many Mediterranean species. Since these are many of the species I especially enjoy, I use a lot of pumice.

So, if expert gardeners almost always add pumice to their potting soil, why don't the potting soil companies makes things easier and just add it for us?

Well, they do, sort of; it's called Cactus Mix. But most people who buy potting soil are simply casual gardeners and don't really understand the importance of drainage.

Adding pumice to potting soils would raise the cost of the soil to the point where the average shopper will think they are overpaying. Pumice is also about twice the weight of potting soil, so the bag would weigh more, a discouragement to most customers.

Finally, when the bag is opened it is going to look different. It's not the dark, rich brown appearance that most people expect from a bag of potting soil.

In the meantime, I just blend some pumice into the potting soil myself. It's easy enough.


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