Will porous clay pots absorb the plant fertilizers .

[Dodi Russell]

I grow some of my cacti in porous clay pots so that they would dry faster. So if the clay pot absorbs water it would do the same by absorbing the plant fertilizers and trapping it in the clay. So I am thinking that this would lead to a decline in the plant's health and signs of mineral deficiency would start to show up .I decided to post this because I noticed that plants I have grown in clay pots grew very slowly and showed signs of stress compared to the ones grown in plastic pots.

So what do you all think, is this true or not or am I just over thinking.
What are your opinions .

[ElieEstephane]

I really like the look of clay pots but plants never really thrived for me in them for the reasons you stated. If you insist on using clay pots, you can see them with whatever is available to you. My favorite is to use the inside and outside with surfboard wax and bake it for a couple of minutes. You can also compensate for water loss with a more water retentive medium which is kind of against the whole reason you use clay pots.

[Steve Johnson]

So what do you all think, is this true or not or am I just over thinking.

Not overthinking -- you are correct about the fact that terracotta pots are a long-term problem because evaporation through the porous clay sets up a sort of competition for water and nutrients between the pot and the roots. Haven't had a chance to do it yet, but I'll post a presentation with photos showing what happens when a Haworthia attenuata I had in terracotta for over 8 years needed a serious repot into glazed ceramic. What you see in the presentation should be interesting.

[DaveW]

Porous clay pots will form a white film of salts on their outsides left behind from water evaporating, therefore in a way they are actually removing salts though I don't think that amount will make a great deal of difference. However it may be a sign the soil needs leaching. I don't know what is available in your region Dodi but in the UK now many of our clay pots are sold as frost proof, being fired at a higher temperature and so no longer porous therefore you never get the white build up of salts on the outside. In that case their walls are no more porous than glazed or plastic pots and behave just the same.

Cacti have been grown successfully in all types of pots, provided either the soil or watering is adjusted for them. After all before plastic we only had clays and they were certainly the porous type in those days.

Have you tried leaching the clay pots?

https://www.youtube.com/watch?v=DrsiNxQ7_P4

An easy way in the growing season is to put the pots out in a rainstorm.

[Steve Johnson]

Cacti have been grown successfully in all types of pots, provided either the soil or watering is adjusted for them. After all before plastic we only had clays and they were certainly the porous type in those days.

While I do agree with you on that point, here's the thing -- rooting behavior in cacti and succulents is different in porous clay than it is in nonporous pots (something I know from direct personal experience). I won't dispute the fact that people have been successfully growing these plants in porous pots for many years, but it's a fair question to ask if their plants aren't able to achieve the optimal long-term growth potential they would have with nonporous pots. I don't mean to be doctrinaire about this subject, so for those of you who do well with porous clay pots, all power to you. The point for me is to give people choices, know what those choices are, then decide on what's best for them given their climate and growing practices.

[Dodi Russell]

Thank you . I removed the plants in clay pots and transferred them to plastic pots. Plants that I repotted are leuchtenbergia principis, lophophora Williamsii and mammillaria plumosa. The leuchtenbergia principis had no roots at all, they were dried and dead . Same with the lophophora willamsii only a few root, most of them dead and stuck to the side of the pot, the tap root was alive. The mammillaria plumosa had a poor root system but it wasn't as worse as the leuchtenbergia principis(this one was severely stressed out and dehydrated) and lophophora willamsii. I think plastic would do better here and would have to stop watering it during the rainy season when it's cooler.

[DaveW]

Leuchtenbergia's like quite a lot of water when growing, particularly to flower, therefore maybe they would do better in plastic since they would stay damp longer? It might have been an idea though for anything not thriving to test the soil with a soil test kit or paper test strips to see what PH it was as this can often change with time after being repotted and roots die.

[Steve Johnson]

It might have been an idea though for anything not thriving to test the soil with a soil test kit or paper test strips to see what PH it was as this can often change with time after being repotted and roots die.

Another good point, although I think you might be missing a bigger one -- use the test strips to test the pH of the water going into the plants.

Dodi, if you've been watering your cacti with hard tap or well water, minerals in the water (usually calcium bicarbonate if it's from a municipal water system) build up in the soil over time. A nasty white residue on the outsides of porous clay pots is a sure sign of this. Mineral buildup slowly robs the roots of their ability to grow and thrive, so if that's what has been happening, porous clay pots are only part of the problem impacting the health of your cacti.

There are 3 options in dealing with the effects of hard water:

• Flush your pots twice a year with rainwater or distilled water. Not the most effective, but it's better than nothing.

• Water your plants with rainwater -- if you can store enough of it to have an ample supply, there won't be any minerals building up in the soil when you use it. This is the easiest solution, but if it's not an option for you...

• Acidify your hard water with 5% white vinegar or citric acid.

I've been acidifying my tap water for 8 years, and the results are quite amazing. I went "whole hog" on this when I started using a pH meter to determine the amount of vinegar I need for proper acidification, although it takes hardcore enthusiasts like me to go that far. For those who aren't so hardcore, pH test strips are good enough to do the job.

IMO your decision to go with nonporous pots is a sound one, and if you can get a handle on the water quality aspect, you're most of the way there. But there's one other aspect we need to look at, and that's your mix. Please describe the ingredients going into your mix, and also the proportions of each ingredient, then we'll proceed.

[DaveW]

Yes agree Steve, but was going on the fact the plants in plastic were doing better than in clay's, therefore assumed they were getting the same water?

I always use rainwater collected from my greenhouse roof in rainy UK, which is always on the acid side of neutral. Our tap water is alkaline since most waterworks make it so because acid tap water corrodes the pipes and in the old days of lead pipes released lead into the water. If you use tap water for many cacti you really need to acidify it as Steve says. Some cacti tolerate alkaline conditions, but not many prefer them. Otherwise you need to keep re-potting to get rid of salts build up.