Tips on increasing soil pH?

[Perrywinkle]

Hello everyone,

I have two species of tree from West Texas, Diospyros texana and Foristiera angustifolia, and both need slightly alkali soil to stay happy. I have the first growing in regular bonsai soil and have been wondering as to why its growth has slowed down until it hit me that my soil pH probably isn't right. Do you guys have any tips on making existing soil more alkali as well as making an alkali soil mixture for when I eventually repot them?

 

[Bonsai Nut]

Add garden lime to the soil. Granular limestone can be mixed into your soil blend and it will be slow-acting. Stay away from hydrated lime, which acts rapidly and can easily be over-applied.

 

[Wires_Guy_wires]

I used limestone flakes in my soil for my longaeva pines. But for quick fixes I use the stuff intended for lawns.

Most tap water is alkaline though, and plants themselves can add or subtract one or two whole pH points in their rhizosphere by secreting acids or bases. If the foliage isn't showing signs of the pH being off, it's probably something else that's halting their growth.

Playing with the pH can be a dangerous game, so make sure you measure often and measure correct. I call it a dangerous game because I don't have enough fingers and toes to count the amount of gardeners I had to help because they went totally berserk with it. Get two points too low and your plants will show signs of all kinds of deficiencies, a few points too high and the same happens on the other side of the spectrum. Then jump back and forth for the rest of the season, tackling all kinds of issues, until the gardener or the plant just gives up. Plants want to correct these values on their own, and they can do that pretty well. If we as caretakers keep countering their countering, we'll just be performing an everlasting dance of hydroxide and hydrogen.. Water is already doing that since the dawn of the universe.

The key takeaway can be summarized in my experience with erythroxylum coca, an acid loving plant from the hillsides and valleys of Colombia: I spent 6 years trying to balance the pH, all kinds of soil mixtures, all kinds of water buffers and continuous measurements.. Until I just gave up and gave them bonsai soil and regular alkaline tap water.. They have never been happier. Best growth output I got in 7 years.

 

[Michael P]

Plants that "like" high pH soils usually do not require high pH, but they have evolved to tolerate it. Most of our West Texas natives are in this category. Although soils in their natural habitat may be basic, they grow perfectly well in neutral or even slightly acidic soils.

You could also import my Dallas tap water--pH 7.8.

 

[Bonsai Nut]

You could also import my Dallas tap water--pH 7.8.

That's nothing. Our water in Orange County was pH 8.5 - as reported in the annual water quality statement(!)

 

[rockm]

These two species don't really "like" alkaline soils, as much as they can tolerate it. The listing for the Desert Olive (Foresteira angustagfolia) is listed as "alkaline adaptable" in the Aggie database of native plants.

Texas Native Plants Database

Same for the Texas Persimmon--"adaptable"

Texas Native Plants Database

I have several native Texas trees, including escarpment live oak, cedar elm and extreme West Texas Gray oak. All are in regular bonsai soil for years. The do fine.

I would look more towards watering practices and other issues for the slow growth. pH is not really a huge issue...

 

[penumbra]

If you have to use lime, I opt for dolometic limestone. Buffers at about 7.0 and supplies magnesium.

 

[Perrywinkle]

Thank you guys for replies. My Texas persimmon has been browning at the tips of new leaves lately and even losing some, which I chalked up to overwatering but now that I think it could be due to the pH. But I will test the soil before adding anything. Do those metal pH testers that you just stick in the soil work well?

 

[Perrywinkle]

These two species don't really "like" alkaline soils, as much as they can tolerate it. The listing for the Desert Olive (Foresteira angustagfolia) is listed as "alkaline adaptable" in the Aggie database of native plants.

Texas Native Plants Database

Same for the Texas Persimmon--"adaptable"

Texas Native Plants Database

I have several native Texas trees, including escarpment live oak, cedar elm and extreme West Texas Gray oak. All are in regular bonsai soil for years. The do fine.

I would look more towards watering practices and other issues for the slow growth. pH is not really a huge issue...

Thank you for clarifying that! My persimmon has been declining ever so slightly and I assumed it was from the abundance of rain we’ve had all summer. Or course I thought it could be from a pH mismatch but I’ll keep an eye on my tree now that I’ve cut back watering to see if it improves.

 

[rockm]

Thank you for clarifying that! My persimmon has been declining ever so slightly and I assumed it was from the abundance of rain we’ve had all summer. Or course I thought it could be from a pH mismatch but I’ll keep an eye on my tree now that I’ve cut back watering to see if it improves.

Watering can become an issue if trees are planted in containers that are too large. Large containers tend to have large areas of soil that stays wet as the roots of the tree don't fill them. Trees benefit from using the smallest container that will fit their existing root mass. Too much rain can make the problem worse. Tilting the pot with a stone or board can improve drainage during these times. Make sure a drainage hole is at the bottom of the lowest side of the tilted pot...

 

[Michael P]

These two species don't really "like" alkaline soils, as much as they can tolerate it. The listing for the Desert Olive (Foresteira angustagfolia) is listed as "alkaline adaptable" in the Aggie database of native plants.

Texas Native Plants Database

Same for the Texas Persimmon--"adaptable"

Texas Native Plants Database

I have several native Texas trees, including escarpment live oak, cedar elm and extreme West Texas Gray oak. All are in regular bonsai soil for years. The do fine.

I would look more towards watering practices and other issues for the slow growth. pH is not really a huge issue...

I just want to give that link an additional endorsement! It is based on the work of the late Benny Simpson, who pioneered the use of Texas natives in built landscapes. He was a mentor, and is sorely missed.

 

[Perrywinkle]

Watering can become an issue if trees are planted in containers that are too large. Large containers tend to have large areas of soil that stays wet as the roots of the tree don't fill them. Trees benefit from using the smallest container that will fit their existing root mass. Too much rain can make the problem worse. Tilting the pot with a stone or board can improve drainage during these times. Make sure a drainage hole is at the bottom of the lowest side of the tilted pot...

Yes I now realize that I did repot the persimmon in too large a pot. I had gotten away with slightly overpotting using pondbaskets and colanders but this time I decided to give the growbags at homedepot a try. I guess the bags don't drain as well, hence problems with too much water in the rainy houston summer.