Alkaline soils are those with a pH above 7.0. In general, trees and shrubs grow best in slightly acidic soils to slightly alkaline soils (pH between 6 and 7.5). In Iowa, soil pH typically ranges from 5.5 to 7.5, with many areas of the state trending toward the higher end of that range. Since soils tend to be in the preferred pH range, gardeners don't often see problems related to soil pH, such as chlorosis or yellowing, unless it is a species that is particularly sensitive to higher pH soils, such as blueberries, pin oaks, or azaleas.
When a soil test shows alkaline soils, it is best to plant trees and shrubs that tolerate higher soil pH. Below is a list of those woody plants.
Shade Trees | Small Statured Trees | Shrubs | High Soil pH Intolerant | More Information
Shade Trees
- Boxelder (Acer negundo)
- Black Maple (Acer saccharum subsp. nigrum)
- Bitternut Hickory (Carya cordiformis)
- Northern Catalpa (Catalpa speciosa)
- Common Hackberry (Celtis occidentalis)
- Katsura tree (Cercidiphyllum japonicum)
- Hardy rubber tree (Eucommia ulmoides)
- Honeylocust (Gleditsia triacanthos var. inermis)
- Coffeetree (Gymnocladus dioicus)
- Eastern Red Cedar (Juniperus virginiana)
- American Sycamore (Platanus occidentalis)
- Eastern Cottonwood (Populus deltoides)
- Bur Oak (Quercus macrocarpa)
- Chinkapin Oak (Quercus muehlenbergii)
- American Basswood (Tilia americana)
- Littleleaf Linden (Tilia cordata)
- American Elm Hybrids (Ulmus spp.)
Small Statured Trees
- Eastern Redbud (Cercis canadensis)
- Yellowwood (Cladrastis kentukea)
- American Smoketree (Cotinus obovatus)
- Hawthorn (Crataegus spp.)
- Crabapple (a few exceptions) (Malus spp.)
- Ironwood (Ostrya virginiana)
- Common Hoptree (Ptelea trifoliata)
- Peking Lilac (Syringa reticulata subsp. pekinensis)
Shrubs
- New Jersey Tea (Ceanothus americanus)
- Buttonbush (Cephalanthus occidentalis)
- American Hazel (Corylus americana)
- Eastern Wahoo (Euonymus atropurpureus)
- Common Witch-hazel (Hamamelis virginiana)
- Winterberry (Ilex verticillata)
- Juniper (Juniperus spp.)
- Beauty Bush (Kolkwitzia amabilis)
- Mockorange (Philadelphus spp.)
- Common Ninebark (Physocarpus opulifolius)
- Fragrant Sumac (Rhus aromatica)
- Common Elderberry (Sambucus canadensis)
- Vanhoutte Spirea (Spiraea ×vanhouttei)
- Snowberry (Symphoricarpos albus)
- Coralberry (Symphoricarpos orbiculatus)
- Chinese Lilac (Syringa ×chinensis)
- Common Lilac (Syringa vulgaris)
- Wayfaring Tree (Viburnum lantana)
- Nannyberry (Viburnum lentago)
Intolerant
- Red Maple (Acer rubrum)
- River Birch (Betula nigra)
- Bicolor Oak (Quercus bicolor)
- Pin Oak (Quercus palustris)
- Azaleas and Rhododendrons (Rhododnedron spp.)
- Blueberries (Vaccinium spp.)