Trees and Shrubs for Alkaline Soil: Recommendations and Tips

1. Mary Meyer, Deb Brown, Mike Zins

2. Table of Contents • Alkaline Soil • Annuals 3 Feet or More • Annual Vines That Grow Quickly • Boulevard Gardens: Perennials • Boulevard Gardens: Small Trees • Broadleaf Evergreens for USDA Zone 4 • Clay Soil • Cold Tolerant Annuals • Compacted Sites: Trees • Crevice Plants • Deer Resistant Plants • Dry Soil: Annual Foliage Plants

3. Table of Contents • Dry Soil: Shade or Under Trees • Dry Soil: Trees • Fragrant Annuals and Perennials • Fragrant Shrubs • Indoor Low Light • Knot Gardens • Lakeshore Native Plants • Long-Blooming Perennials • Rain Garden Plants

4. Table of Contents • River Banks and Canoe Public Access Areas • Self-Seeding Perennials • Septic Mound Plants • Shade: Shrubs • Shade: Small Trees • Shade: Tall Perennials • Steep Slopes • Trees That Produce Minimal Litter • Under a Black Walnut Tree • References

6. Trees for Alkaline Soil: honeylocust • Gleditsia triacanthos inermis honeylocust, 30-60’ thornless varieties are vest, provides filtered shade, rapid grower, tolerates many soil conditions • Buckeye, bur oak, hackberry, green ash, smokebush, and silver maple are also good trees for alkaline soils.

7. Small Trees for Alkaline Soils Ironwood: Ostrya virginiana 25-40’ Interesting hoplike fruits in fall and brown leaves add winter interest, native. Smokebush, 6-15’ Chokecherry Iowa State photo

8. Hydrangea: Great Shrubs for Alkaline Soil Hydrangea arborescens hills of snow hydrangea 3-5’ tall; Spreads 3-5’; mop-head blooms Hydrangea paniculata panicle hydrangea 6-8’ Showy white to pinkish blooms in summer. Endless Summer® Hydrangea macrophylla 'Bailmer' Requires acidic soil for blue color pH 5.0-5.8; blooms on current season wood. pink in alkaline soil pH 6-7.

9. Lowering Soil pH for Blue Hydrangea Flowers • Before planting:1) Have your soil tested for initial pH level. Sending a sample to the University of Minnesota Soil Testing Laboratory soiltest.coafes.umn.edu 2) If your soil pH is less than 5.5 the only amendment suggested before planting is to mix in sphagnum peat moss into your soil at the rate of 1 to 2 cubic ft per plant. (use a blend of 50% native soil to 50% sphagnum peat)3) If your soil pH is greater than 5.5, incorporate elemental sulfur into the top 6 to 8 inches of soil at the following rates to reduce your soil pH by 1 unit:For sandy soils - 1.0 lb per 100 square feet (about 2 cups)For loamy soils - 2.5 lb per 100 square feet (about 5 cups) For example, if the pH of your loamy soil is 6.0, incorporate 5 cups of elemental sulfur per 100 square feet (or ½ cup per 10 square feet). After mixing in the elemental sulfur, mix in 1 to 2 cubic feet of sphagnum peat moss per plant.

10. Lowering Soil pH for Blue Hydrangea Flowers • After planting:1) Periodically retest your soil pH. Do not add any acidifying amendments if your soil pH is 5.0 or less.2) Use ammonium sulfate as the nitrogen source at the rate of 1 lb (or 2 cups) per 100 square feet (or a little less than a ¼ cup per 10 square feet). Ammonium sulfate is the best nitrogen source to help maintain soil acidity. 3) If your soil pH is greater than 5.5, use aluminum sulfate to help lower your pH and supply available aluminum at the same time. Mix about 1 lb (2 cups) of aluminum sulfate per 5 gallons of water and then apply the solution around the drip line of the plant. Repeat the application on a monthly basis as long as your soil pH is greater than 5.0. Caution - over application of aluminum sulfate can be toxic even to hydrangea. Carl Rosen, Soil Scientist, U of Minnesota

11. More Shrubs for Alkaline Soil • Lilac • Juniper • Barberry • Cotoneaster • Lilac • Viburnum

12. Perennials for Alkaline Soil yarrow astilbe clematis sweet William coneflower daylily coral bells phlox hosta salvia

14. Boulevard Gardens: Small Trees • Syringa reticulata Japanese tree lilac 15-25’ Long-lived and cold tolerant; scented ivory flowers are an early summer hallmark; interesting winter seed pods.

15. Boulevard Gardens: Small Trees • Amelanchier laevis Alleghany serviceberry 15-25’ Minnesota native; large flowers; excellent red fall color; delicious edible purple fruits attract birds in summer. • Malus hybrids crabapple 15-25’ Tough and hardy in Minnesota; scab can be a conspicuous foliar disease, look for resistant varieties; many flower colors provide vivid displays; various shades of green foliage and winter interest with yellow or red fruit.

16. Boulevard Gardens: Small Trees • Acer tataricum ssp. ginnala amur maple 20-30’ Lightly scented May flowers are followed by double serrated dark colored leaves with lighter undersides; excellent fall color; hardy, adaptable; grown as a free-form clump, standard, or a well-groomed hedge; self-seeds. Minnesota Tree Care Advisor photos

18. Perennials for clay soil Russian sage coneflower feather reedgrass,‘Autumn Joy’ sedum sedum hosta and daylilies

20. Trees for Compacted Sites • Acer rubrum red maple 50-70’ Round crown, transplants readily, ‘Northwood’ and ‘Red Sunset’ have nice fall foliage; MUST HAVE MOIST SOIL.

21. Trees for Compacted Sites • Betula nigra • river birch • 40-70’ • peeling cinnamon-brown bark, often multi-stemmed

22. Trees for Compacted Sites • Celtis occidentalis hackberry • 40-60’ Vase-like habit, easily transplanted, very adaptable. • May be slow to establish • Native to MN

23. Trees for Compacted Sites • Fraxinus nigra black ash 40-70’ Large black buds, ‘Fallgold’ recommended for fall color. • Fraxinus pennsylvanica green ash 40-60’ Fast growth, deep shade, broad rounded form, seedless varieties.now overplanted? tough urban tree, emerald ash borer

24. Trees for Compacted Sites • Larix laricina larch, tamarack • 40-70’ native, deciduous conifer, • yellow fall color, few pests

25. More Trees for Compacted Sites silver maple cottonwood cottonwood

27. Deer Resistant Plants chives and onion; Allium spp.

28. Deer dislike mugo pine, shown here on tortoise island at the Japanese garden, Minnesota Landscape Arboretum

29. ageratum

35. Shrubs for Shade azaleas viburnum barberry and boxwood

36. Diervilla; bush honeysuckle

39. Under a Black Walnut Tree

40. Order from the shop.extension.umn.edu or Distribution Center: 1-800-876-8636