Wednesday, October 17, 2012

Size Matters (Containers Part 2)

A promising start with a sad ending
Containers are tricky solutions to growing vegetables. One of my first experiments in growing vegetables garnered grape-sized beets.  After weeks of fertilizing and watering, I ate the world's smallest beet and goat cheese salad.

This summer, I tried growing cherry tomatoes in a self-watering Trader Joe's container, 11" diameter, 11" deep. The plant didn't fruit and ended its sad life in the compost bin.  My problem, I realized, was container size.

Obviously, big plants need big pots. But how big?

Container Size Recommendations
Jeff Gillman and Meleah Maynard, the authors of Decoding Gardening Advice, say that most vegetables need to be grown in a pot at least 20" wide and 16" deep. Their recommendations:

Most fruiting plants (such as tomatoes, beets, carrots, and peas)
20" diameter x 16" depth

Some less-thirsty fruiting plants (such as peppers, eggplant)
15" diameter x 10-12" depth

Greens (such as spinach, lettuce) and herbs
10" diameter x 10-12" depth

Jessie Banhazl at Green City Growers recommended slightly smaller minimums. She told me to plant fruiting plants in a minimum of 12 inches depth, or more for larger plants.

For tomatoes, zucchini, or summer squash
2 square feet

For cucumbers, eggplant, peppers, tomatillos, chard and collards
1 square foot
(I've also grown both peas and beans in square foot containers)

Consider the plant too, Jessie said. Leafy greens need more surface than depth to grow well. So a short windowbox is much better suited to arugula than to carrots.

For every plant there is a container
My grape beets were in a long, narrow plastic container only 8" deep. Their tap roots hit the bottom and they stopped growing. That container is now used for spinach and lettuce. And the Trader Joe's pot? My heirloom basil flourished in it for the rest of the summer.

Other Container Tips
  • Water (and drainage!)   Everyone knows it's easy to forget to water your plants. But drainage is important too - I'll be drilling a few extra holes in one of my containers to avoid water-logged plants next year.
  • Fertilizer: Frequent watering (or rainfall) will wash nutrients out of the soil. Remember to replace with an organic fertilizer, like compost tea or Neptune's Harvest.

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