i have pondered this before ....

i figured that most are made from recycled material ... and it wasnt worth the cost of purifying the material to create a white material ... nor the added cost of painting them white .. which would probably fail anyway .....

pure speculation ...

ken

I acquired some used pots from a nursery last summer and they were green.

I could not get an answer from the google machine

ron

Yep, probably the least expensive to make and yet the worst color choice for any plant that sits in them in direct sun.

And yet.........wholesale growers use them almost exclusively and typically have them lined out in rows in full, all day sun!!

Not such a bad thing if the containers become at least partially shaded by the plants in front of them, though those that endure full sun will have those black pots heat up to the point that one can't maintain their hand upon them, which obviously isn't good for the roots. I learned the hard way when purchasing an expensive conifer and placing it where it received unobstructed all day blazing sun. The sun angle is lower where I live and dang if that specimen didn't end up having it roots killed off several inches into the pot. I now either set up a bit of shade for the containers or spray paint them white, just be sure to first use sandpaper or the paint will easily scratch off depending on the brand used.

I have noticed that those black pots really don't get as hot as I would expect. They certainly don't get as hot, or retain the amount of heat, as many other materials I have lying around my yard. To me, at least, they seem to be made out of some sort of heat resistant material. I could def be wrong, though. .

I always thought it was due to black being the cheapest colorant or it’s just the hodgepodge of recycled plastics to get black

" hodgepodge of recycled plastics "

That could be reason enough for them to blacken the plastic, so they end up with a uniform color.

Well, this picture shows what Lonicera caerulea roots think about black plastic pots

I didn't say that I liked black pots, just stated a reason why possibly they make them. :-)

I know zippo about this but I'm going with Matt's explanation!

Somewhat relevant to the topic

https://www.hortweek.com/growers-going-revolutionise-recycling-taupe-plant-pot/ornamentals/article/1489052

A local nursery uses pots made from rice hulls. They eventually disintegrate if left outside but it is surprising how long they last. They are brittle; if you are too aggressive getting the plant out they shatter, but then I just put the shards on the compost pile.

hugg's pic above is startling .... the white tag made all the difference.. wow ... ken

Maybe the pots are not really black. Maybe the kettle just calls them that.

hoovb holds the keys to the universe

Let's not go there. :-)

Am unsure as to why most pots being used are black, though Huggorms's photo obviously demonstrates of the heat build up and damage done to the root system of plants .... thus, reason being I like to spray paint them white.

Interesting.........I grow most of my plants in containers. Granted, a lot are in very ornamental glazed ceramic pots, but just as many are not and those that are not are almost 100% in black plastic nursery pots, as I can get them any size I want (professional association with my local nursery) and they are lightweight, durable and ideal for larger plantings.

I have been doing this for going on 30 years and I have never encountered a situation where the heat through the plastic damaged or 'cooked' the root system. I just don't think it is that big a deal......if one stays on top of the care of the containerized plants. And if was that much of an issue with the masses of wholesale growers that live and operate in my part of the world, then I have no doubt the pots would be widely available in colors other than black!

Well, certainly can't exactly be optimal conditions for plants that might prefer having a cooler root zone. I guess, the sun just must be hotter where I live, lol, since I can't maintain my hand upon the south facing side of black pots situated in full hot sun. Next summer, I'm gonna do a bit of an experiment and take temperature readings.

Oh, just found this former thread ...

[Can black pots cook roots?[(https://www.houzz.com/discussions/can-black-pots-cook-roots-dsvw-vd~2111205)

I think black's hotter too..I found this..

We lay down mulch to keep the sun from baking the ground, why would soil in a black pot be any different?

I try to give my outside pots shade, no matter what color.

I think this entire issue is somewhat overstated :-) As I mentioned previously, this part of the country - actually most of the entire west coast - is home to literally hundreds of wholesale growing operations......what supplies most of the eastern retail nurseries. And without exception, they all line out black-potted, containerized plants on vast stretches of real estate in full sun. And typically with a heavy duty black weed blocking fabric underneath. I've worked for several of these places so can speak with a degree of first hand knowledge. If 'cooking the roots' or overheating container soils was that much of a serious issue for these growers, one would have thought they would make some serious changes to their growing methods. They do this to make money, afterall, and the margins of a wholesale growing operation are slim enough as it is.....they can't afford to lose a lot a of stock!

But they haven't and they don't lose much, if any, stock from overheating so exaclyl how big a deal is it??????

I don't think anyone is saying black pots should be banned..just that if given a choice would a lighter color be better..I HAVE seen plenty of stressed/dying/dead plants in garden centers in black pots..with perfect care a black pot might not matter but maybe if planted in a lighter colored pot they would be a little healthier?..

I have little doubt that black nursery containers lined out in fields can produce satisfactory results when arranged to become at least partially shaded by one another ... though, I still would not consider such as ideal. Overheating and root damage IS something that many of us have experienced and consider serious enough to warrant taking precautions against. Maybe, we all can discuss this further by meeting up at a nursery on a blazing hot summers day, naysayers are requested to be fully dressed in black.

Root Heat in Containers

"Maybe, we all can discuss this further by meeting up at a nursery on a blazing hot summers day, naysayers are requested to be fully dressed in black."

Have worked in the nursery industry - both the wholesale and retail ends - for going on 30 years and I am here to tell you that this is not nearly as a big a deal as most folks try to make out!! If it were, growers would be experiencing huge losses.......and they are not. Granted, they are dealing with more than 1 or 2 pots and they have probably a lot more experience behind them but overcooked/overheated plants are very uncommon, likely due to an appropriate layout and adequate and timely irrigation practices.

For home gardening purposes - athough I do not find it at all necessary - it is very easy to purchase pots in a variety of colors, but most are unlikely to be inexpensive nursery grade pots. Or do a pot-in-pot method. It is really NBG!!

"Appropriate layout" means placement of containers to provide a certain amount of shading for the pots themselves, right?

Matt had the correct answer - carbon black is the cheapest way to stabilize plastics for outdoor use. Leave a transparent gallon milk jug outside and after a couple years it will shatter to pieces due to UV degradation. OTOH I have black plastic pots I've been reusing for over 10 years.

There are chems that can protect white plastic - I'm just guessing stilbenes off the top of my head - but they are more expensive.

If wholesale growers have slim margins, it makes sense that they would not switch to more expensive, white UV-stabilized pots, especially if cultural practices (pot layout, irrigation) are able to minimize ill effects from high root zone temperatures caused by black plastic in full sun.

Being able to work around a limitation, and being motivated to do so for reasons involving cost, does not mean the limitation isn't there.

Gardengal, what do summer air temperatures run in those areas on the west coast with all the wholesale nurseries? I found a reference stating pot-in-pot production originated in the south to protect roots from extreme summer temperatures, but I don't know if that had more to do with pots heating up in the sun or pots heating up because they are above ground and the air temperatures are 100°+.

Wholesale nurseries in some parts of western California definitely have a problem with black pots. Rowed out sock can definitely have a problem if on the sun-exposed edge. Roots are cooked. (University-based research verifies that.)

Even home gardeners may have a problem. I always slipped my plastic growing pots inside larger decorative pots to fend off direct sunlight.

Jean,

who gardened in Long Beach, CA (a mere mile from the beach) for 30-some years.

I've been in the industry for around forty years. For some of them, I managed a wholesale nursery in southern South Carolina and all of our beautiful plants were in black plastic pots. As were every single plant in all of the many nurseries I've been to all over the deep south.

The container world is changing, mostly for marketing and display. These plants are grown in an enormous, gutter-connected range. I'm thinking this has nothing to do with soil temperature but rather eye appeal.

T.O. Plastics latest offer of colored tray inserts

Ya, who cares about the roots, I want pretty! lol

I ended up with a Terra Cotta pot last spring so they must be in circulation already.

One of my favorite nurseries for annuals uses the different colors to represent different price points. So the black pots are $1.95, the terracotta are $2.95, and the yellow are $3.95. Cuts down on clerks ringing things for the wrong price, unless they are color blind. 😉