Plants That Produce
Pot Culture
By Richard Frost
Remember that nearly all plants require drainage when planted in a container. This needs to be achieved by a moderate distribution of holes in the bottom of the pot and also by choosing a soil that percolates. Resist the temptation to place rocks at the bottom of a pot. This can adversely affect the soil pH, become a home for diseases, etc. If you are concerned about soil leaking out of the holes, use instead an appropriate size hardware cloth such as ¼ inch mesh. Also, be careful about placing flat-bottomed pots on a flat surface. Raise the pot so it will drain completely by placing it on a few masonry chips or the “pot feet” sold at local nurseries. This will also reduce staining on outdoor surfaces.
Of the brand-name soils, I recommend Kellogg Garden Patio Mix™ for a plant that will be potted less than 5 years either indoors or outdoors. For annual veggies and ornamentals, you might also consider a mix of worm castings, horticultural sand, and perlite. For long-term container plantings you need a soil with drainage that will not break down into dense material over time. This is especially crucial with fruit trees and larger ornamentals. For this situation I like a mix of worm castings, ground peat, horticultural sand, and scoria (¼ inch horticultural pumice). The initial organic matter will break down and leach out over time. Keep a layer of ½ to 1-inch diameter mulch on top to provide continuous replacement.
Avoid watering the plants with a tray under the pot. You do not want that water full of leached salts and invading microbes being drawn back up into the pot over the next several days. In fact, avoid self-watering pots with the exception of hydrophilic plants. Instead, water the plant(s) where the excess can drain off elsewhere – then put a tray underneath to catch the few remaining drops if you must.
Now what to plant in the containers? Certainly the invasive herbs such as mints, oreganos, and thymes all belong in their own pots. For lettuces and salad greens, consider growing 3 or 4 individuals or clumps in a trough-shaped container. A scrap piece of 8-inch diameter drainage pipe cut in half the long way works great for this. I like growing tuberous vegetables in an 8 or 10-inch pot and then just dumping out the contents when I think they are ready. If not, back in the pot the tubers and soil go!
Many types of fruiting plants also do well in containers. Keep in mind that tomatoes will produce a crop to the extent that they have roots. Hence, a tub is recommended for most varieties. Blueberries and Huckleberries do not like our native soil or water, so a container is actually the best place to grow them. Guavas and Pomegranates are extremely tolerant of pots. Finally – if you have room for a 40 to 60 gallon tub in full sun, consider one of these container-tolerant fruit trees: Panache Tiger fig, dwarfed Anna apple, dwarfed Katy apricot, dwarfed Artic Star nectarine, dwarfed Eva’s Pride peach, dwarfed Burgundy plum, dwarfed Oroblanco grapefruit, dwarfed Cara Cara navel orange, or the standard Gold Nugget mandarin.
SDHS member Richard Frost is also a member of the California Rare Fruit Growers.
For copies of past articles and more information, please see www.plantsthatproduce.com.
Reprinted with permission from March 2009 "Let's Talk Plants," the newsletter of the San Diego Horticultural Society, www.sdhortsoc.org
© 2009 San Diego Horticultural Society