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Optimum Soil pH Levels for Plants | The Old Farmer's Almanac

Soil pH Levels for Plants

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Optimum Soil pH Levels for Trees, Shrubs, Vegetables, and Flowers

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What is your soil’s pH level? Every plant prefers a different level of acidity. Use this soil pH chart to find which pH level is best for your garden plants. Then, learn how to adjust it accordingly!

The Secret of Soil pH

Having the right soil pH is key to growing a healthy garden, but it’s a factor that’s often overlooked in favor of nutrient levels and soil consistency. While these are also crucial things to consider, the pH of the soil plays a major role in how well your plants can absorb the nutrients you provide them, so it’s important to get it right!

The wrong pH often won’t kill plants outright, but it can affect their growth and result in subpar blooms or crops, depending on how sensitive the plant is. In actuality, many plants are able to adapt to a range of pH levels. Hydrangeas, for example, produce different colored flowers depending on whether they’re grown in acidic or alkaline soil.

A pH of 6.5 is just about right for most home gardens, since most plants thrive in the 6.0 to 7.0 (slightly acidic to neutral) range. Some plants (blueberries, azaleas) prefer more acidic soil, while a few (ferns, asparagus) do best in soil that is neutral to slightly alkaline.

How do you find out your soil pH? To do a simple pH test, you can acquire a soil pH test kit online or from a local garden store. However, for a similar cost (or even for free), you may be able to have your soil tested by your state Cooperative Extension, which can provide a much more in-depth analysis of your soil (including nutrient levels and other helpful bits of information). 

Here’s another way to figure out your soil type.

How Do You Adjust Soil pH?

Once you figure out your soil pH, it may be necessary to adjust it to suit the needs of the plants you’re growing. The level of acidity will specify the amount of soil amendment that is needed to bring it up or down to the appropriate level. Acidic (“sour”) soil is counteracted by applying finely ground limestone or wood ash, and alkaline (“sweet”) soil is typically treated with gypsum (calcium sulfate), ground sulfur, or compost.

Read more about preparing soil for planting.

Optimum Soil pH Levels for Plants

Common Name Optimum pH Range

Trees and Shrubs

Apple 5.0-6.5
Ash 6.0-7.5
Azalea 4.5-6.0
Basswood 6.0-7.5
Beautybush 6.0-7.5
Birch 5.0-6.5
Blackberry 5.0-6.0
Blueberry 4.0-6.0
Boxwood 6.0-7.5
Cherry, sour 6.0-7.0
Chestnut 5.0-6.5
Crab apple 6.0-7.5
Dogwood 5.0-7.0
Elder, box 6.0-8.0
Fir, balsam 5.0-6.0
Fir, Douglas 6.0-7.0
Hemlock 5.0-6.0
Hydrangea, blue-flowered 4.0-5.0
Hydrangea, pink-flowered 6.0-7.0
Juniper 5.0-6.0
Laurel, mountain 4.5-6.0
Lemon 6.0-7.5
Lilac 6.0-7.5
Maple, sugar 6.0-7.5
Oak, white 5.0-6.5
Orange 6.0-7.5
Peach 6.0-7.0
Pear 6.0-7.5
Pecan 6.4-8.0
Pine, red 5.0-6.0
Pine, white 4.5-6.0
Plum 6.0-8.0
Raspberry, red 5.5-7.0
Rhododendron 4.5-6.0
Spruce 5.0-6.0
Walnut, black 6.0-8.0
Willow 6.0-8.0

Vegetables

Asparagus 6.0-8.0
Bean, pole 6.0-7.5
Beet 6.0-7.5
Broccoli 6.0-7.0
Brussels sprout 6.0-7.5
Cabbage 6.0-7.0
Carrot 5.5-7.0
Cauliflower 5.5-7.5
Celery 5.8-7.0
Chive 6.0-7.0
Cucumber 5.5-7.0
Garlic 5.5-8.0
Kale 6.0-7.5
Lettuce 6.0-7.0
Pea, sweet 6.0-7.5
Pepper, sweet 5.5-7.0
Potato 4.8-6.5
Pumpkin 5.5-7.5
Radish 6.0-7.0
Spinach 6.0-7.5
Squash, crookneck 6.0-7.5
Squash, Hubbard 5.5-7.0
Tomato 5.5-7.5

Flowers

Alyssum 6.0-7.5
Aster, New England 6.0-8.0
Baby’s breath 6.0-7.0
Bachelor’s button 6.0-7.5
Bee balm 6.0-7.5
Begonia 5.5-7.0
Black-eyed Susan 5.5-7.0
Bleeding heart 6.0-7.5
Canna 6.0-8.0
Carnation 6.0-7.0
Chrysanthemum 6.0-7.5
Clematis 5.5-7.0
Coleus 6.0-7.0
Coneflower, purple 5.0-7.5
Cosmos 5.0-8.0
Crocus 6.0-8.0
Daffodil 6.0-6.5
Dahlia 6.0-7.5
Daisy, Shasta 6.0-8.0
Daylily 6.0-8.0
Delphinium 6.0-7.5
Foxglove 6.0-7.5
Geranium 6.0-8.0
Gladiolus 5.0-7.0
Hibiscus 6.0-8.0
Hollyhock 6.0-8.0
Hyacinth 6.5-7.5
Iris, blue flag 5.0-7.5
Lily-of-the-valley 4.5-6.0
Lupine 5.0-6.5
Marigold 5.5-7.5
Morning glory 6.0-7.5
Narcissus, trumpet 5.5-6.5
Nasturtium 5.5-7.5
Pansy 5.5-6.5
Peony 6.0-7.5
Petunia 5.5-6.0
Phlox, summer 6.0-8.0
Poppy, oriental 6.0-7.5
Rose, hybrid tea 5.5-7.0
Rose, rugosa 6.0-7.0
Snapdragon 5.5-7.0
Sunflower 6.0-7.5
Tulip 6.0-7.0
Zinnia 5.5-7.0

Learn more about testing your garden’s soil.

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