Gardening in Alkaline Soil: Strategies and Plant Choices

If you live in the western U.S., chances are you have alkaline soil. Alkaline soils are typical in arid western regions, while acidic soils occur in high-rainfall areas (northwest, eastern U.S.). Knowing your soil type matters because pH affects nutrient availability. Alkaline ("sweet") soils have pH >7; acidic <7. Most plants tolerate slightly alkaline (7–7.5), but problems arise above 7.5—nutrients like iron become unavailable, causing iron chlorosis (yellow leaves with green veins, stunted growth).

Let's explore determining alkaline soil and dealing with it: amendments to lower pH, containers/raised beds, and using plants adapted to alkaline soils—perhaps the easiest, most sustainable solution.

How to Test Your Soil pH

Test before adding plants or amendments. Garden centers carry basic soil pH kits (easy to use). Neutral pH=7; acidic <7; alkaline >7. If test shows high pH (>7.5), consider professional testing through county extension.

What to Grow in Alkaline Soil

Native plants.

Choose plants native to your area—they've adapted to local soil and climate, a low-maintenance choice. Generally, plants adapted to arid climates and drought tolerance handle alkaline soils well.

Browse plants native to the U.S.

Shown: Firecracker penstemon, a Southwestern native

Plants from similar climates.

While natives are first choice, plants from regions with similar soils and arid climates work too: Australia, Mediterranean, parts of Africa.

Australia:

Arid Australia contributes beautiful flowering plants tolerant of alkaline soils: Blue Bells (Eremophila hygrophana 'Blue Bells', zone 8), feathery cassia (Senna artemisioides, zone 8), purple lilac vine (Hardenbergia violaceae, zone 9), Valentine bush (Eremophila maculata 'Valentine', zone 8).

The Mediterranean:

Mediterranean plants also do well: Jupiter's beard (Centranthus ruber, zones 4–9), lavender (Lavendula spp., zones 6–8), rosemary (Rosmarinus officinalis, zones 8–10), yarrow (Achillea millefolium, zones 3–10).

Shown: Prostrate rosemary (Rosmarinus officinalis 'Prostratus')

Shown: Moonshine yarrow (Achillea x 'Moonshine')

Shown: Jupiter's beard (Centranthus ruber)

Plants that handle acidic or alkaline soils.

Good if you don't know your soil type. Flowering favorites: candytuft (Iberis sempervirens, zones 4–8), clematis (Clematis spp., zones 4–11), coral bells (Heuchera sanguinea, zones 3–9), cranesbill (Geranium sanguineum, zones 4–9), meadow sage (Salvia nemorosa, zones 4–8), bridal wreath spiraea (Spiraea prunifolia, zones 5–9), weigela rubidor (Weigela florida 'Rubidor', zones 4–8).

Shown: Coral bells (Heuchera sanguinea)

Shown: Cranesbill (Geranium sanguineum)

How to Amend Alkaline Soil

If you want to grow acid-loving plants, lower pH with amendments.

Sulfur.

Several forms correct highly alkaline soils (pH >7.5). Elemental sulfur incorporated into soil is least expensive but slowest. Follow package instructions. For iron chlorosis (yellow leaves, green veins), try iron sulfate (sulfur + iron). Ammonium sulfate (nitrogen + sulfur) also works faster than elemental sulfur.

Compost and manure.

Incorporate organic matter (compost, manure) before planting as long-term pH-lowering solution. Apply organic mulches (bark chips, compost, manure, pine needles) once or twice yearly to keep pH from climbing.

Note: Lowering pH of alkaline soils is challenging and continual. Limestone naturally present constantly releases lime. Many western water sources are slightly alkaline, contributing to alkalinity when watering.

Other Ways to Enjoy Acid-Loving Plants

Despite challenges, some must have azaleas, blueberries, gardenias, rhododendrons. Plant in pots—but western water is often alkaline, so feed with acidifying fertilizer to keep dark green. Raised beds also help for neutral to slightly acidic pH.

Shown: Gardenia with white gaura (Gaura lindheimeri) in container

Sadly, many try to grow acid-lovers in alkaline soil with disappointing results. Iron chlorosis is most common symptom: light green/yellow leaves with dark green veins, stunted growth.

While you can amend regularly, or use containers/raised beds, wouldn't it be easier to select from the many beautiful plants that thrive in "sweet" soils?

Shown: Gardenia suffering from iron chlorosis in alkaline Arizona soil

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