| What is soil pH and why should you care? Soil pH is an indication of the acidity (sourness) or alkalinity (sweetness) of a soil. The pH scale goes from 0.0 to 14.0, with 0.0 being most acid, 14.0 being most alkaline and 7.0 being neutral (neither acid nor alkaline). 
Why is this important? Because soil pH has a very strong influence on plant growth. It affects soil bacteria, nutrient leaching, nutrient availability, toxic elements and soil structure.
Of the 17 essential plant nutrients, 14 are obtained from the soil. Before a nutrient can be used by plants it must be dissolved in the soil. A pH range of 6 to 7 promotes the most ready availability of plant nutrients. Extremely and strongly acid soils (pH 4.0 to 5.0) can have high concentrations of soluble aluminum, iron and manganese, which can be toxic to the growth of some plants which prefer alkaline soil.
Plants such as azaleas, rhododendrons, blueberries, white potatoes and conifer trees require acid soils to grow well. Others do well only in slightly acid to moderately alkaline soils. A pH above 7.4, for example, can cause problems with the availability of iron to pin oak and a few other trees. This causes yellowing of the leaves, putting the tree under stress and possibly leading to decline and death.
The structure of your soil, especially if it’s clay, is affected by pH. In the optimum pH range (5.5 to 7.0) clay soils are granular and easily worked. But if the soil pH is either extremely acid or extremely alkaline, clays tend to become sticky and hard to cultivate.
What’s the solution? Dolomite lime is usually added to acid soils to increase soil pH. The addition of lime not only raises pH eliminating most major problems associated with acid soils, but it also provides 2 nutrients (calcium and magnesium) to the soil. Liming materials are relatively inexpensive, comparatively mild to handle and leave no objectionable residues in the soil. They can be applied slowly (over a period of months) to raise your soil pH. If you apply them in the fall, they will have a chance to begin raising the pH of your soil over the winter.
One accurate method of determining soil pH is with a pH meter. A second method involves the use of indicators or dyes. Many dyes change color with an increase or decrease in pH making it possible to estimate soil pH. Kits containing the necessary chemicals and color charts are available at our garden center. Or a soil sample can be sent to the Analytical Services Lab ( Spaulding Life Science Center , Room G-54, 38 College Road ) at UNH in Durham (03824). Depending on the quality of your soil, pH test should be made every one to three years to determine the need for lime and other nutrients. To obtain a soil testing form call UNH Cooperative Extension’s Family, Home & Garden Education Center ’s Info-Line toll free at 1-877-398-4769. Trained volunteers are available to answer your questions Monday through Friday from 9:00am to 2:00pm.
PH VALUES OF FLOWERS, TREES, SHRUBS GRASSES, FRUITS AND VEGETABLES
* Low number represents acidic soil preference
* High number represents alkaline soil preference
Flowers, Trees & Shrubs:
Azalea 4 ½ - 5 ½
African Violet 6 – 7
Ageratum 6 – 7
Alyssum 6 – 7
Anemone 6 – 7 ½
Arborvitae 6 – 7
Aster 5 – 6
Amaryllis 5 – 6
Alder 6 – 7
Andromeda 5 – 6
Ash 6 – 7
Begonia 5 ½ - 6 ½
Butterfly Bush 6 – 6 ½
Bottlebrush 6 – 7 ½
Birch 4 ½ - 6
Bayberry 4 ½ - 6
Beech 6 – 7
Boxwood 6 – 7
Batchelor Button 6 ½ - 7 ½
Cedar 5 – 7
Cypress 5 – 6
Cottoneaster 6 – 7
Cottonwood 6 – 7 ½
Chestnut 5 – 6 ½
Carnation 6 – 7 ½
Caladium 5 ½ - 6 ½
Canna 6 – 7 ½
Croton 5 – 7
Chrysanthemum 5 ½ - 6 ½
China aster 5 – 7
Dogwood 6 – 7
Daffodil 6 – 8
Dahlia 6 – 7
Delphinium 6 – 7 ½
Deutzia 6 – 7
Daphne 5 ½ - 6 ½
Elm 6 – 7
Euonymus 6 – 7
Eucalyptus 6 ½ - 7 ½
Forsythia 5 ½ - 6 ½
Fir 5 ½ - 7
Fern 5 – 6
Fuchsia 5 ½ - 6 ½
Gardenia 5 – 6
Gladiolus 5 ½ - 6 ½
Geranium 6 – 7 ½
Hibiscus 5 – 6 1/2
Holly 5 – 6
Hydrangea (Blue) 4 ½ - 5 ½
Hydrangea (Pink) 6 ½ - 7 ½
Hawthorn 6 – 7 ½
Hyacinth 6 – 7
Hazel (Witch) 6 – 7
Hemlock 5 – 6
Honeysuckle 6 – 7
Horsechestnut 6 – 7
Iris 6 – 6 ½
Ilex 5 – 6
Ivy 6 – 7
Juniper 5 – 6
Lantana 5 ½ - 6 ½
Lily 5 – 6
Larch 6 – 7
Laurel 5 – 6
Locust 6 – 7
Lilac 6 – 7
Linden 6 – 7
Lily of the Valley 5 – 6
Magnolia 5 – 6
Marigold 5 ½ - 7
Maple 6 ½ - 7 ½
Mulberry 6 – 7
Narcissus 6 – 6 ½
Oak 5 – 6
Orchid 4 ½ - 6
Palm 5 ½ - 7
Pansy 5 – 6 ½
Peony 6 – 7 ½
Periwinkle 6 – 7 ½
Petunia 5 ½ - 7
Phlox 5 – 6
Pine 5 – 6
Plane Tree 6 – 7
Poinsetta 6 – 7
Poplar 6 – 7
Privet 6 – 7
Quince 6 – 7
Rose 5 ½ - 7
Rhododendron 4 ½ - 5 ½
Snapdragon 6 – 7
Spirea 6 – 7
Spruce 5 – 6
Sweetgum 6 – 7
Sycamore 6 – 7 ½
Tulip 6 – 6 ½
Tupelo 6 – 7
Tuliptree 6 – 7
Verbena 6 – 7 ½
Violet 6 – 7 ½
Viburnum 6 – 7
Walnut 6 – 7
Weigelia 6 – 7
Willow 5 – 7
Wisteria 6 – 7 ½
Yew 6 - 7
Yucca 6 - 7
Zinnia 5 ½ - 7
Grasses
Blue (Ky) 5 ½ - 7 ½ Bent 5 ½ - 6 ½
Bermuda 6 - 7 Buffalo 6 – 7 ½
Clover 5 ½ - 7
Fescue (red) 5 ½ - 6 ½
Fescue (tall) 6 ½ - 7 ½
Rye 5 ½ - 8
Rye (Perennial) 6 - 7
St. Augustine – 6 – 7 ½
Zoysea - 4 ½ - 7 ½ Fruit and Vegetables
Alfalfa 7 – 7 ½
Apple 5 ½ - 6 ½
Artichoke 6 – 6 ½
Asparagus 6 – 6 ½
Barley 7 – 7 ½
Bean 5 ½ - 6 ½
Beets 6 - 7
Blackberry 5 ½ - 6 ½
Broccoli 6 – 6 ½
Brussel Sprout 6 – 6 ½
Cabbage 6 – 6 ½
Cantaloupe 6 – 6 ½
Cherry 6 – 6 ½
Cauliflower 5 ½ - 6 ½
Chive 6 – 6 ½
Corn 5 ½ - 6 ½
Cranberry 4 ½ - 5
Carrot 5 ½ - 6 ½
Cucumber 6 – 6 ½
Celery 6 – 6 ½
Eggplant 5 ½ - 6 ½
Grapes 5 ½ - 6 ½
Grapefruit 6 – 6 ½
Lemon 7 –7 ½
Lettuce 6 – 6 ½
Lima Bean 6 – 6 ½
Mushroom 6 – 6 ½
Onion 5 ½ - 6 ½
Peas 6 – 6 ½
Parsley 5 ½ - 6 ½
Peach 6 – 61
Pear 6 – 6 ½
Pepper 5 ½ - 6 ½
Potato (Sweet) 6 – 6 ½
Potato 5 – 5 ½
Plum 6 – 6 ½
Pumpkin 5 ½ - 6 ½
Rhubarb 5 ½ - 6 ½
Rice 5 – 6 ½
Rye 5 ½ - 6 ½
Radish 6 – 6 ½
Soybean 6 – 6 ½
Spinach 6 - 7
Squash 5 ½ - 6 ½
Strawberry 5 – 5 ½
Turnip 5 ½ - 6 ½
Tomato 5 ½ - 6 ½
Watermelon 5 ½ - 6 ½
Wheat 6 – 7
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