Watering Potted Plants in AZ Heat

art_in_ovJune 3, 2012

Flowers and vegetables thrive in the ground from uniform temperature and moisture. Pots expose the soil on all sides to heat and dryness. For potted plants to send roots deep, I assume one should water deeply and not too often, regardless if using a watering can or drip system. My plants are alive, but not growing.

Does someone have an ideal formula to grow plants in pots here in AZ?

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kathleen10(z9b AZ)

There are 2 important things to think about with containers: keeping them moist and keeping the roots sheltered from excess heat.

For the heat issue:
*Some people use a double pot, a smaller one planted inside a larger one, to insulate the roots. If you look at the thread here titled "What's looking good (or bad) in June", you'll see a photo there of a sweet pea planted in a double pot.
*Use very large containers to keep the roots placed further inside the pot rather than up against the pot walls where the heat is higher.
*Shade the outside of the pot to keep it cooler. Placement can help as can planting shading plants (like zucchini, for example) around the pots.
*Some people even wrap their pots with insulation of some kind to get heat protection.
*Black pots are notorious for heating up even hotter than other colors as black seems to concentrate the heat, so best not to use them.

As for moisture, the key thing is keeping the soil in the root zone moist. Doesn't mean to keep them soaking wet, the soil surface should dry out a bit before watering again but if you stick your finger in the soil to 1-2-3" deep, it should feel cool which means it's still moist. If it's not cool, big trouble for the plants.

Some ways to deal with water:
*Check the containers daily and especially later in the summer you may have to water once or more than once per day depending on how small the container is and how porous it is.
*Porous containers dry out faster (terra cotta) than non-porous (glazed ceramic, plastic).
*Use the Moisture Control potting soil that you can purchase as Lowes, Home Depot, etc. It helps hold moisture longer to safeguard container plants.
*Whatever you do, use a good potting soil so you have something that will indeed hold some water and yet still drain - native soil might either be so sandy the water will not be held or so silty it will never allow good roots to develop (for standard plants, not cacti, they need lightness, oxygen and water for best growth).
*Use a drip irrigation system that ensures consistent watering.
*Use ollas - these are buried porous ceramic containers that are filled with water which the roots can migrate to in order to get moisture from the wall of the container as it seeps through and out into the soil. You can purchase these (expensive) or make them using 2 terra cotta pots siliconed together with the bottom drain hole closed w/silicone. Ollas must have their top opening covered or else you are inviting mosquitos to breed in them, but with a good size olla, you only need fill it once per week or so.

I happen to garden almost completely in containers because I can put them up high enough on pedestals and encase them in netting to repel the rabbits and quail that try to eat everything being watered out here in the rural desert of the North Valley. I use extra large containers (20" and up), some have Moisture Control soil, almost all of them have ollas (DIY type) and none are terra cotta or black. I've had success with many herbs and flowers, tomatoes, peppers, okra, eggplant, chard, onions, lettuces, squash, bamboo so far. The ollas are new this year but I believe they are helping already to ensure nothing ever has a dry hour which means major wilt and possible death for a container plant. Sometimes they will bounce back but not all the time. The ollas are like insurance in case I miss a daily water check/irrigation.

Hope this helps.

    Bookmark   June 4, 2012 at 1:03AM
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Pagancat(Phoenix, AZ)

I like the ollas idea, Kathleen, thanks. I'm trying out some pots after some massive failures, lol.

    Bookmark   June 4, 2012 at 11:44AM
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tomatofreak(Z9 Phx USA)

I agree with much of what Kathleen says, e.g., bigger pots, no black pots, shade for container coolness, etc. I have most everything in pots, too. Everything from 8" - 12" all the way up to half-barrels. I have some plants in old galvanized wash tubs. I line metal pots with sheets of styrofoam, often stuff that comes as packing in boxes. This year, I'm using some inexpensive plastic pots and I lined them with multiple sheets of kraft paper. I let other plants grow around the bottoms of the containers to help cool the roots.

I haven't had a lot of success with MG's Moisture Control soil. A key ingredient to plant growth is oxygen. A couple of years ago, I read about using wood chips to aerate the soil and since have read this article in MEN. I will say that every container that I've added wood mulch to has healthier plants than the ones that don't.

About the ollas: If you buy these things, they are ridiculously expensive. I solved the problem by buying terra cotta (unglazed) wine coolers at the thrift stores. You will find most of them come complete with a lid that solves the mosquito problem. No lid? Just turn a saucer upside down over the top.

I wish I could say that my container 'gardens' are a complete success, but that is not the case. It's a matter of soil, plants, water, light, shade, temperature and a host of other factors. Experiment and keep notes. You'll figure out some of it. ;o)

Here is a link that might be useful: Wood mulch

    Bookmark   June 4, 2012 at 12:39PM
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kathleen10(z9b AZ)

Pagencat! Is that really you? I thought you were in TN green grass - are you back in the VotSUN or just popping in to check on us? The ollas ARE making a difference for me, no worries over a delayed watering now.

Tommie, good idea on the thrift store buys and great tip on the wood chips. I made several ollas in the fall from pots I had and just siliconed a new matching terra cotta saucer on top, turned over and plugged the hole with a cork. Then... I found BIG 8"+ pots at the 99cent store so I made a whole batch of even bigger ollas. Kind of messy with the silicone but the price is right at $2/each.

My latest container adventure is a dishwasher box. Yup, left the wood & heavy paperboard reinforcements in place and then lined it with a lot of newspaper, bottom and sides, put some compostibles in the bottom and then filled with soil. Once filled I wrapped in landscape burlap and tied with horse hay ties. Pretty cute and so far so good. My Italian pole beans are going great guns in there up scavanged Chilean mesquite branches with 2 ollas and a nice thick mulch of super dried horse manure/shavings mix. I'd like to get a couple more boxes and do sweet potatoes and yardlong beans, just need to find a box source.

    Bookmark   June 5, 2012 at 3:38AM
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Pagancat(Phoenix, AZ)

Hey, Kathleen - yup, I'm back >wavingNever knew the horses would be so handy for gardening, lol... I've been cleaning up most of their manure in an effort to keep the fly population down. I'm jealous of your dishwasher box - so far I've filled to good sized compost bins and a hole in the ground .... and this is in not even a month and a half. I better start digging out some beds or I'm going to be in deep doo-doo, if you know what I mean.... = )

    Bookmark   June 5, 2012 at 11:55PM
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kathleen10(z9b AZ)

Wow, coming back into the frying pan, eh? :) Waving back, nice to see you too :) I suppose it's culture shock from both locations now for you guys. Whole different worlds.

So are you in the same place as before or have you got horse property here now? There used to be some grandfathered in down there not far from your old stomping ground.

As for composting manure, we don't do much of that. Instead we spread it so it can dry in our searing sun, pretty much kills off the bugs. I use that dry "fluff" for top dressing and a sort of slow release manure "tea" that gets a bit steeped with each watering. It looses a lot of its nutrients when allowed to dry but still retains some. And it's great for amending the heavy, sandy soils too when worked in. Oh and fly predators work pretty good too. Can't get rid of flies with horses but sure can cut them way back.

So you just got back here, sounds like. I bet you are very busy working on gardening projects to get things more as you like them out in the yard. Not to mention all the moving fallout/project stuff that crops up. Welcome home :)

    Bookmark   June 6, 2012 at 4:11AM
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grant_in_arizona(USDA Z9 Scottsdale AZ)

Fun posts! I love them. I do love growing a lot of plants in containers in addition to in the ground--my patio is shamefully full of pots and plants, but I like it and it's fun for me.

You've gotten some GREAT tips and advice, so definitely see what works for you. The only tiny tidbit I'd mention is if you need to water frequently, it helps to have nice, porous soil. When I know I'm going to have a plant in a pot that needs a lot of water, I add a lot of perlite or pumice, it really helps keep rot and various bacterial/fungal issues at bay. Good luck, let us know of any adjustments, and keep us posted!

Take care,

    Bookmark   June 6, 2012 at 8:24PM
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haname(z9 AZ NE Phoenix)

Grant, what are your preferred soil mixes for the various types of plants you grow in containers? (i.e., succulents, citrus, annual flowers, houseplants)

    Bookmark   June 7, 2012 at 3:40PM
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grant_in_arizona(USDA Z9 Scottsdale AZ)

Great question! I wish I had a great answer, LOL. In general I just use Miracle Grow regular "potting soil" and add some perlite, or pumice, usually one part perlite/pumice to two parts potting soil, always with a nice thick layer of perlite/pumice at the bottom of the pot before I add any "soil", to help with drainage.

Of course, if I'm in a rush, or low on supplies, all guidelines go out the window, LOL, but in general, I like really fast draining soils even for fluffy/leafy things. For true desert cactus I might work up to 50% pumice, but most just get the regular mix.

Here's a pic from this week of my patio. It doesn't have all of the petunias, pansies, and geraniums that I grow autumn through spring, but it still has a container or two, and there are plenty of pots of vincas in the wings, just starting to bloom.

Fun discussion, I love hearing how different people grow things. Thanks for everyone who has posted questions and replies, it's so fun!

Happy gardening all,

Here is a link that might be useful: Pics, so far, from my garden June 2012

    Bookmark   June 7, 2012 at 4:36PM
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don't think i saw anyone mention it above..

if your plants are on a sun exposed patio, use pots with feet or otherwise get them off the concrete/tile/flagstone. this helps roots not cook :)

ceramic feet can be pricey, i cut a plank into a bunch of strips.

    Bookmark   June 11, 2012 at 6:51PM
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grant_in_arizona(USDA Z9 Scottsdale AZ)

That is such a GREAT tip, xoxos, I'm glad you mentioned it! Having "feet" on the pots really does help. You can see in my pics several of my containers have built-in feet to keep the pot elevated off of the hot patio, and for those that don't, I do keep a bunch of ceramic and plastic "feet" to tuck under the pots. That inch or three of space really does help keep them cooler. I'm so glad you reminded us to mention it. I also use a lot of small metal plant stands for individual pots that hold the plants up off of the hot patio., and you can see from some of these pics I'm also a fan of plant stands, oink oink oink.

Great tip!

Happy gardening all,

Here is a link that might be useful: Pics, so far, from my garden June 2012

    Bookmark   June 11, 2012 at 8:07PM
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