Semi-Hydro and Alkaline-Loving Plants - Orchid Board

Plantcrazed101 · #1 01-08-2017, 12:39 PM

Hi y'all,

This is slightly off topic, but I have a Cubanola domingensis that prefers alkaline soil. I've adjusted it to semi-hydro, and it has produced a beautiful set of roots! The only thing is, the plant is yellowing. Since I haven't been using anything other than my regular fertilizer and it hasn't really had much of a change in conditions (it's in slightly warmer, brighter conditions as I have moved it out of isolation..doesn't appear to be based on my research sensitive to light levels increasing a bit) my only guess is that the source of it's yellowing leaves has to do with it needing more alkalinity.

Since I'm sure I'll have orchids that need more alkaline water, how do you do that with semi-hydro? How much is too much?

estación seca · #2 01-08-2017, 12:47 PM

I recommend you check the pH of the water in your reservoir just before watering. You can get pH test strips or liquid kits at aquarium shops. Yellowing leaves in Rubiaceae typically represent insufficient nitrogen or iron.

Orchid Whisperer · #3 01-08-2017, 02:53 PM

__IF__ you are willing to grow in a non-semi-hydro manner, you can plant in a typical potting soil to which limestone chips or chunks have been added. If you can't get your hands on limestone chunks, use broken concrete (the cement in concrete is made from limestone).

I have an orchid (Bletia patula) that grows on shallow limestone soils in the Carribbean. I got a tremendous improvement in growth when I moved it from traditional orchid media and into an organic soil which includes some orchid bark and charcoal, but also organic potting soil, chips of concrete, and crushed eggshell.

With my orchid and your tree lily, "alkaline" really may mean only a neutral to slightly basic pH. See if a soil pH between 7 and 8 is adequate for your plant (just slightly on the alkaline, or "basic" side of neutral pH). That shift in pH will have a big effect on the plant uptake of various plant nutrients.

Plantcrazed101 · #4 01-28-2017, 12:01 PM

Hmm...for some reason I never got the updates that anyone had replied! So thanks y'all for the replies...I still have questions though

I'm wondering what are the best aquarium strips to use? I got some a while back but they didn't have a number, just different colors...so then I was guessing still about the PH.

What I like about Semi-Hydro is that I don't have to worry about the clay being a weird PH, so I'm really only dealing with the water and fertilizer that I use + how often I water and what ever other factors I may be missing.

Orchid Whisperer · #5 01-28-2017, 01:20 PM

Quote:

Originally Posted by Plantcrazed101

Hmm...for some reason I never got the updates that anyone had replied! So thanks y'all for the replies...I still have questions though

I'm wondering what are the best aquarium strips to use? I got some a while back but they didn't have a number, just different colors...so then I was guessing still about the PH.

What I like about Semi-Hydro is that I don't have to worry about the clay being a weird PH, so I'm really only dealing with the water and fertilizer that I use + how often I water and what ever other factors I may be missing.

With pH strips or paper, it should come with a color scale so that you can match the color obtained to a number on the pH scale. You can get pH paper with a range from 0 to 13 (you shouldn't need up to 14) or a mid range paper with a range from 5.5 to 8.0. It would not surprise me if other intermediate ranges are available.