What is pH?

Scientifically speaking, pH is the “potential of hydrogen ions” measured in an aqueous solution. The result of this will be either acidic or alkaline, based on the Unified pH Scale. This scale typically ranges from 0 to 14, with 7 being pH neutral. In a garden, having a proper level of pH for your plants could be a matter of life or death!

 

Measuring Your pH 639px-PH_scale

Checking your indoor/outdoor garden’s pH regularly is key to having a healthy harvest. Whether it’s in soil, hydro, or coco-coir, every plant species has it’s own personal preference for pH levels. A pH of roughly 6.5 is perfect for common home gardens, since most plants thrive in the slightly acidic to neutral range (6.0-7.0). However, not all plants are the same and some research should always be done to ensure every last plant’s needs are met. 

To measure your pH in soil, it may be necessary to purchase a digital soil pH monitor or have it tested professionally by contacting your local county’s extension office (such as UCONN). After a successful measurement, the pH can then be adjusted to the desired range by using store bought boosters or with limestone (brings pH up) and gypsum/ground sulfur (brings pH down). In hydroponics, there are liquid pH indicators that can change colors to visually show you the exact pH of your water, as well as digital pH monitors and indicator color strips. To counteract inaccurate pH levels in water, it is typically best to use liquid boosters and continuously monitor the levels throughout the grow season. 

 

pH Levels for Common Plant Species:

 

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 6.0-7.5
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

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