Choosing A Planting Container In Hot Climates, Part 1: Plastic

Many people will talk your ear off about the benefits of cutting stress out of your life. Listen to them, they are right! Plants are no different. When kept in containers they have some options to manage stress, but ultimately we have the responsibility of giving them the tools they need to succeed. To do that, start by choosing the correct pot, then you can think about placement and climate among other things.

We’ll start with plastic, because I know it best, and it is easily accessible. Here is some practical advice for warm, arid environments.

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This guide will utilize a favorability number system, 1 being poor, 5 being exceptional. For price, $ means single digits, $$ means double digits, et cetera.

Plastic

Durability: 2
Price: $-$$
Aesthetics: 2
Water retention: 3
Insulation: 2-3
Weight: 5

“PP” = Polypropylene, “HDPE” = High Density Polyethylene, “GF” = Glass Filled

Starting with plastic is a no-brainer for me. They are light weight, and their size will determine their insulation quality. They last roughly two years in the desert southwest if they say “PP” on the bottom. PP means polypropylene, a cheap plastic. Arizona sun just tears these materials to pieces. If you live in a higher elevation, less light-intense climate like Flagstaff, AZ I would rate these a 4 for you. They may even last you 4 years, but I’ll need some confirmation on that because I’ve never lived up there (leave a comment!). Still, they can break from normal use when brittle, and they will get used.

It is rare to find a pot marked “GF”. This plastic has fiberglass particles suspended in it before it is injected into the mold. Highly durable, but the quality still depends on the plastic type. Glass filled PP will deteriorate at the same rate in sun and you’ll start getting fiberglass hairs everywhere. In your skin especially. Glass filled nylon is one of the most durable of these, but is rarely used in planting containers. Below is a trowel from Ikea marked Polyamide-6, a nylon, which has been manufactured using glass in the mixture. See the link at the end of this page for tips that will extend the life of your plastic containers.

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Small buckets (5 gallons or smaller) would score a 2 or a 3 for insulation in the desert southwest where heat penetrates easily. Shade cloth or the cover of a tree works wonders to regulate the temperature in these buckets. Bigger volume means the soil can provide its own insulation. I suggest purchasing 20-gallon buckets (like my blue ones!), found at most hardware stores for relatively cheap.

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Taken two days after winter solstice, 2016. Daytime high: 67F, the sun warms these barrels, but the warmth only penetrates about 3 inches.

Aesthetics-wise, these planters are a 2 because their style is industrial, and garden aesthetic favors earthy colors and materials. Though in my personal opinion, grow where ever and however you can. Some planters can be styrofoam or other types of plastics that are molded to look like stone or terra cotta, but there is no replacement for the real deal. That being said, you CAN grow beautiful things in plastic containers here in this heat.

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A work in progress, but a good case-in-point.

Planting in plastic

  • Add soil to 2-3 inches from the top
  • 1 inch of water will penetrate 1 inch deep, BUT
  • Slow-water to make sure it penetrates the entire containers-worth of soil
  • Plants won’t send roots to the outer 2 inches of soil in summer, unless place in full shade, otherwise they will seek shelter in the middle of the container

In cold weather, 1 gallon black plastic containers like what you’d buy a plant in are perfect if you are on a budget. Fill them with soil and leave them in the sun in the winter to grow leafy greens or garlic. Plant herbs, peas, or cold weather tomatoes in larger sized containers. The soil warms up nicely in the sun and plants are happier. Water once per week or as needed if the weather is warmer than usual.

I use 5 gallon white buckets for winter planting!

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In the summer, soil dries out easily regardless of pot material, so keep it amended, and water once every 2-3 days. If you live in a place like Flagstaff, use your own discretion, or check the comment on this post for suggestions. For plastic, amending with organic material and mulching are your best bets to hold moisture in. Remember to add compost or a fish emulsion as well, because water and organic matter alone won’t be enough. For more about managing your garden in the heat, check out Protecting Cucumber Plants From Heat Stress In Zone 9A.

Do you live in a cooler southwestern climate? I’d like to hear about your plastic containers, and your experience with them.

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