Plants with special fertilizer needs
Some cold hardy trees balk at our soils. You can alter the soil when the tree or shrub is small, but adding enough fertilizer to make a difference becomes more difficult as tree grows.
Sugar maple can become a sickly yellow in alkaline soils, and may even die. Silver maple will likely survive, but the leaves can turn yellow. Both trees will benefit from an acidifying fertilizer, which will release the iron in the soil.
A more direct option is to add iron chelate, a treated (and very expensive) form of iron which is immeditely available to the roots. Adding ammonium sulphate, Miracid, or iron chelate to the soil around maples can alleviate the problem temporarily. However, because trees develop such large root systems it is unlikely that fertilizer will provide a permanent solution to iron deficiency. One should consider other trees if your Ph is high. At the very least, plant only one maple tree and see how it does before filling your yard with them.
Hydrangea prefer acid soils. Because they are a shrub and have relatively small root systems, it is a good idea to dig out some of the existing soil and replace it with peat, which is naturally acid, before planting. After planting, regular treatments of an acidifying fertilizer will make for a more vigorous plant.
All evergreens can benefit from acidifying fertilizers. Evergreens are native in areas with acid soils. As one moves east across Minnesota away from the Red River Valley, evergreens begin to appear in the wild, a sure sign that the soil is becoming more acid. Although evergreens are not native to the Red River Valley, many varieties can grow healthily there. They will be even more healthy if given regular doses of an acidifying fertilizer.
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