Alkaline-tolerant means a plant can still pull iron and manganese out of the ground when the soil pH is high enough to lock most of it away. Across Delta and Montrose counties that is ordinary ground — commonly 7.5 to 8.2 — so this is not a bonus trait here. It is the baseline.
The failure it prevents is iron chlorosis, and once you can see it you will see it everywhere in this valley: leaves gone pale yellow or almost white while the veins stay green, worst on the newest growth at the tips of branches. The plant is not short of iron. The iron is in the soil and chemically unavailable, and the plant is starving next to it.
Chlorosis is not fatal quickly. It is worse than that — the plant declines for years, looking progressively thinner and sicker, while somebody feeds it and waters it and wonders what is wrong. Silver and red maple, pin oak, river birch and quaking aspen are the ones we see it on most, all of them excellent trees somewhere with different dirt.
Treatment exists and it is a treadmill. Chelated iron applied to the soil or the leaves greens a plant up for a season, sometimes two. It does not change the pH, so it has to be repeated for the life of the plant. A soil acidifier moves the number temporarily and then the native ground and the irrigation water pull it back.
Which is why the plant list is the answer and the amendment is not. Choose something that is adapted to alkaline ground and the problem never begins.
The other end of the same problem is worth understanding before anybody falls in love with a plant that cannot have it. Azalea, rhododendron and blueberry are acid-loving — they need the pH below 6.5, and on this ground that is a container with its own soil and its own water, not a bed.
