I got curious about Ingrid's bright red Dark Lady, and checked the info. on bloom color: soil high in phosphorus gives a color-shift to the red range, soil high in aluminum sulfate gives a color-shift to the blue range, regardless of the pH. The drawback of using aluminum sulfate is its reaction with phosphorus fertilizer to form solid.

I have already seen how sulfur kills earthworm, and the vote in the Soil Forum is "No" to sulfur in soil. Acidify alkaline water to neutral is more gentle on earthworms that putting acid into soil. I'm leaning more toward SOLUBLE phosphorus to solve alkalinity, since potassium phosphate is lowest in salt-index. At pH above 7 phosphorus is tied up with magnesium in clay soil, or calcium hydroxide (lime) in tap water.

Some plants roots are more effective in secreting acid to unlock phosphorus from soil. The link I posted earlier "Acid phosphatase in plants' root" described cluster-root in secreting acid to draw out phosphorus in soil. Dr. Huey falls in that category ... my neighbor put a bed of Hybrid teas grafted on Dr. Huey and they bloomed like mad, even in our pH 7.7 rock-hard alkaline clay. Phosphorus is essential for root growth and blooms production.

The problem with some OWN-ROOT Austins that are stingy in alkaline soil: England has a high rainfall, pH of rain is acidic around 5.6. A vast region of England is acid to neutral soil pH. The type of roses that thrive in that wet acidic soil, won't do well as OWN-ROOT in a dry and alkaline soil. If David Austins select the roses with roots that secret acid, there would be a build-up of acid in an already acidic soil, leading to aluminum toxicity.

What I like about buying roses bred in the same climate and soil as mine is: They bloom well even when I water them with alkaline tap water. The own-root Romanticas and French Meilland roses bred in France, bloom well in 100 degree heat and alkaline clay. For 1st year gallon-size own-roots: Firefighter, a Meilland gabe 80+ blooms. Romanticas Sweet Promise, Bolero, Liv Tyler all gave me too many blooms that I have to share with neighbors. Frederic Mistral gave 10 blooms since his roots are locked in my gluey creation of clay, peatmoss, aflafa meal, plus sulfur. Kim Rupert's Annie Laurie McDowell and Lynnie can't be beat in bloom-production. I had to give Annie fertilizer high in nitrogen so she would stop blooming and produce growth.

Recently I threw a bucket of tomatoes on top of composted banana peels. They glued up into a hardened sheet. I would need a leaf shredder to break that up. I should had known better from my chemistry classes NOT to mix acid with base, they from solids. Peatmoss at pH of 4 binds up with alkaline clay elements. I didn't know until I dig up roses and found what once made fluffy: sulfur, clay, peatmoss, alfalfa meal ... became concrete chunks months later. Plants become yellowish in hardened clay since their roots can't breath.

The best way to fix heavy clay for roses is with BOTH coarse sand with pebbles (neutral and don't break down), and composted fine pine bark to keep it moist, so the sand won't be baked under the sun to make potteries with clay. I dug those holes up many months later and they are still fluffy. Folks root roses' cuttings in sand ... wimpy own-root roses are best in sandy soil, not rock-hard clay.