Yes, it can prevent fungal spores from splashing from the dirt onto your plant. Why one should cut off all tomato leaves touching the ground. It keeps sun off the dirt, so keeps pots cooler. Dirt is dark so absorbs light, thus heat. using say pine straw will absorb less heat. Sometimes you want heat, not often, but sometimes.

I have kind of thought about the heat aspect. Yet, nursery pots are always black.

"Yet, nursery pots are always black."

They work well holding heat in green houses, under filtered light. Most seedlings need heat too. If I saw black pots outside, I would not buy that plant. Fabric pots are the best for heat dissipation.
Also the more moisture you can retain the better. the more you water, the more chance of fungal infections. Why I never would use 5-1-1 for vegetables. It needs frequent watering, does not contain mycorrhizae. Mycorrhizae increases PH range for nutrient absorption.
The fungi can deliver nutrients in a wider ph range than the plant roots alone. Soil structure is often mentioned for good root structure. Mycorrhizae is more important than soil structure. It can help grow roots in pure mud.
Both together is best. Many ways exist to have a good soil structure.

" If I saw black pots outside, I would not buy that plant. Fabric pots are the best for heat dissipation."....
Well, there certainly are some interesting comments about this subject. I am not sure how much time people here spend in retail nurseries....but, if one refused to buy plants in black nursery pots...they would never be buying any plants. As of today...I have NEVER seen a retail nursery selling plants in fabric pots.
I am guessing that in areas like deserts in west Texas and the like...black pots would definitely cook the roots. However, with our mild SoCal weather (75-80 degrees temps) I do continue to wonder how influential the black pots really are...

I have worked at several wholesale growers, all without exception, grew in black nursery pots. Some in hot inland locations, some in cooler coastal areas. The pots are in open fields covered with landscape fabric, the pots in most cases, one gallon size, close enough to touch each other. All were watered by overhead sprinklers, during the heat of the day. To succeed as a grower the plants must be sold and moved out. Most plants will quickly fill the pots with roots and must be sold and moved before that happens, or watering and soil temperatures DO become a problem. Many growers have orders for their plants, before they are grown. Al

For my own uses, I prefer either light colored plastic pots, or unglazed terra cotta. Anything that arrives in black plastic will be re-potted into something more suitable for my own uses.

I'm not a big fan of fabric containers... but then, the types of plants I grow in containers remain in those same pots for at least 2 years, sometimes longer... and most will have to be moved indoors when autumn rolls around, and then back out after the danger of frost in spring passes.

I have beds, both raised and otherwise, for vegetables and herbs and the like... so my main container growing is confined to tender bulbs, houseplant type specimens, small trees, and other comparable, and more perennial items.

Personally, I wouldn't use a separate layer of mulch on top of the medium within a container. It can make watering... knowing when it's needed... kind of deceptive... and differing layers within one pot can create perched water tables, where moisture tends to sit due to the way moisture behaves in medium/pots.

There really is no one-size-fits-all answer to most gardening/growing questions, though... mainly because we each have varying degrees of things like climate, weather, light amount, local environment, and micro-environment to contend with... plus... plant types, pot sizes, differing mediums, amount of time devoted to growing, feeding schedules, etc...

And while the basics of plant culture remain the same, we each must contend with our very own differences. What works marvelously for one grower might not work at all for another... because of these differences. The devil is in the details, as they say.

Al mentions landscape fabric... and to me, this is one of the most awful things the industry has ever created! I despise it! I refuse to work with it! I have worked with it, and it was the biggest pain in the rear end I ever came across! Never again!

So, you see... one size does not fit all... my preference is to use a very organic approach to growing in the garden... and to use a more inorganic approach when it comes to growing in containers.

Of course, Al references a commercial grower establishment, a situation in which that landscape fabric probably saves a lot on labor, and/or on lost moisture... giving them an edge.

When it comes to most of my container grown plants, they receive mostly morning (eastern exposure) sunlight, which isn't as strong as that of afternoon. By about 12:30pm, the direct sunlight is no longer beating down on my containers... and for the rest of the afternoon, they'll receive reflected light from the white garage siding.

Or, I'll keep some containers in the dappled light under trees or shrubs, so they're protected from the harshness of direct sun, but can still receive enough light for decent growth.

But my situation won't match anyone else's... certainly not perfectly. When I was learning, gaining knowledge about the plants I wanted to grow, I read a lot and asked a lot of questions... and I took the information that made sense, given my own situation, and I left the rest behind. I read everything with a huge grain of salt and lot of common sense...

A "green thumb" is not luck, and it's not good fortune... it's nothing more than applied knowledge!

Happy Gardening!

Landscape fabric can be great. If you have a nursery set up, landscape fabric fabric covering the ground with pots on top will keep the roots from going into the ground and possibly picking up disease or pests.

Drew, you would never be able to buy any plants in CA except for 24" boxes and up if you refused to buy plants in black plastic nursery containers.

The re ason they are black is for UV resistance.

I like composted leaf mould and grass clippings. It keeps the roots a bit cooler, protects against drying out and provides nutrients for the plants.

I have grown tomatoes and peppers in 5-1-1 with great results.
Mycorrhizae can be added to any soil mix, good soil structure can not.

"Mycorrhizae can be added to any soil mix, good soil structure can not. "

Yes they can be added, but will die in 5-1-1. Soluble fertilizer has been shown to kill the fungus. Well documented.
I also have had great results in 5-1-1 but better results in mixtures with manure compost.
Again 5-1-1 has the worst soil structure destroying compost I know of...peat moss. It has little nutritional value, breaks down super quick, is hydrophobic. No one disputes these claims. All I suggest is to use a better compost. Peat moss was originally used in soil mixes to decrease shipping weight. When you don't understand something, look at the bottom line.

It's not composted manure in commercial mixes that makes them muck right? it's peat moss, do you not agree?
Nobody uses other composts in potting mixes, unless you buy the super expensive organic mixes, which btw, are fantastic and work great. Like Happy Frog, or Organic Mechanics. Both top rate potting mixes. The key is not to put too much compost in potting mixes. Just enough to support beneficial bacteria and fungi. The added benefits have been mentioned, disease resistance, less watering, less polluting runoff, etc.

This post was edited by Drew51 on Thu, Jul 17, 14 at 17:48

"Yes they can be added, but will die in 5-1-1."

Why?

Drew, I do not dispute your preference of compost over peat. Mixing 1 part of 7 of either will not turn the whole container into useless muck. If you'd rather use compost, fine. I'll probably experiment with it myself at some point. You do have to watch your compost though, my dad used some that had grass in it that was treated with broadleaf weed killer. Yikes...That did not bode well for the tomatoes!

The statement "Yes they can be added, but will die in 5-1-1." is not entirely accurate.

High rates of fertilizers, especially phosphorus, inhibit the formation of mycorrhizae, not kill it. Organic forms of fertilizers seem to have less inhibitory effect on mycorrhizae than inorganic, soluble fertilizers. I mostly use maintenance dose of organic ferts every time I water.

Compost does not always contain Mycorrhizal fungi. They are not present in composts unless the compost contained plant roots. If the compost has been heated from microbial activity, then the mycorrhizal fungi may have been killed. Some composts may be compatible with mycorrhizal fungi, but others may have high salt or nutrient content that can inhibit mycorrhizal fungi.

If you use a soil with compost and mycorrizae, or add mycorrhizae, you still need to add fertilizer.

Lol - Drew is so intent on discrediting me and the soils many here use that he will say almost anything, no matter how absurd - things like mychorrizal fungi can make up for a lack of oxygen in the rhizosphere, that mychorrizae will die in the 5:1:1 mix, the more moisture a soil holds - the better ..... it never ends.

All I use is soluble fertilizers. If I repot a plant growing in the 5:1:1 mix OR the gritty mix in spring or fall, I always find mychorrizal fungi in the soil, so the contention that soluble fertilizers (all fertilizers are eventually soluble, btw, otherwise they couldn't make it into the nutrient stream is hooey. Many organic growers say the soluble fertilizers kill soil life, which is also ideological baloney.

Many people shun mychorrizal inoculations because of the severe impact reductions in the volume of the fungi have on the plant and production. Example - you have a tomatoe plant that has a symbiotic relationship with the fungi. Your plant develops a blight and you treat with a fungicide. Oops - there go the mychorrizae and now there aren't near enough roots to support the top of the plant because root systems in symbiosis with mychorrizal fungi are much smaller than root systems w/o the fungi ...... so it's not all just one big rosy picture. The same thing can happen when the soil temp gets too hot and the fungi die.

Take this statement: "Again 5-1-1 has the worst soil structure destroying compost I know of...peat moss. It has little nutritional value, breaks down super quick, is hydrophobic." Peat is actually finished compost, mostly lignin, which breaks down very slowly - and who cares if it has no nutritional value - finished compost made of any material has very little nutritional value ...... and who wants to sacrifice the structure of the soil in an attempt to have the soil feed the plant when getting nutrition to the plant is monkey easy.

It doesn't matter whether you use a small fraction of compost or a small fraction of composted sphagnum moss in your soils. The only reason it's in the 5:1:1 mix is because it's a handy way to adjust water retention. Neither are meant to provide a source of nutrition.

Al

"...the super expensive organic mixes, which btw, are fantastic and work great. Like Happy Frog..."

...which includes "soil structure destroying" sphagnum peat moss as its second ingredient.