My soil is deficient in potassium. Earthco. that tested my soil stated that 1/3 of soil is deficient in potassium, for strong stems, fight diseases, improve color, and reduce water usage. Since potassium stay put where it's applied, rather than moving down like nitrogen - I'm checking on the best potassium to put in the planting hole, I still have 24 roses to put in the ground (they are in pots now).
I'm after strong stems for the strong wind here. I must had put at least 20 banana peels in the planting hole of Radio Times. It has huge & sturdy stems. There are other choices for potassium:
1) Rose-tone, which the instruction says to use 3 cups along with peat-moss. This sounds excessive for a 18" wide hole. I once used Acid-Tone in the planting hole of a white pine and burnt it, so I'm cautious.
2) Green sand, supplies marine potash, silica, iron oxide, magnesia, lime, phosphoric acid and 22 trace minerals. It's sold for $10 for 5 lbs., expensive for breaking up clay.
3) Kelp meal is quick-released. I don't know if this would be water-soluble enough to reach down to the root-zone if applied to the surface of established plants.
4) Sulfate of Potash - SteveinAustralia in HMF recommended this one. Same question as above. Below is a link to sources of potassium.
It would be nice for droopy Austin roses to have strong necks & healthy, less thirsty, and better color. Any info. about potassium would be greatly appreciated. Thank you.
Here is a link that might be useful: Organic Sources of Potassium