Plants flourish when their roots thrive. Conventional wisdom is that germs thrive in soil that provides nutrients and structural support and allows water and air to circulate freely. The ground must also sustain the beneficial bacteria and fungi that help roots absorb nutrients. The origins of most plants function best in soil ranging from pH 6 to 7.5.

All true, but gardening in the Flagstaff area often requires adding an element to this sage advice. Creating an open patch of ideal soil exposed to the elements is rarely the best approach in our climate. The ground will dry out, and the plants will be battered by wind and sun. Consider how you can create a hardscape to hold your soil in place, keep it moist, and protect your plants from the wind and overnight frosts.

Soils in the Flagstaff area tend to be shallow, heavy in clay, and alkaline. Shallow, clayey soils prevent the development of solid and deep roots. Clay-heavy soils also contain the free circulation of water, oxygen, and carbon. Alkaline soils chemically inhibit nutrient uptake, especially iron, phosphorus, and manganese.

• Determine the pH and texture of your soil. Inexpensive devices for measuring pH are available in garden supply stores. A simple test for evaluating consistency is to moisten your soil and squeeze some of it in your hand. If it falls apart quickly, it is loose and will probably not retain water well. If it sticks together tightly, it is perhaps heavy in clay and will not allow adequate water and air circulation. If it holds together yet appears porous, the texture may be fine, but the soil may still lack nutrients. Nutrient levels in local soils are typically relatively low but if you’re unsure, consider having your soil professionally tested.
• Amending problem soils with organic compost is the single most effective way to adjust pH, improve texture, add nutrients, and increase water-holding capacity. Compost is commercially available but reads the label to be sure it is made from natural, uncontaminated ingredients. Ideally, begin making your compost in a rodent-proof bin and use it when establishing new plantings or as a top dressing and mulch. Adding acidic amendments such as sulfur or coffee grounds can benefit alkaline soils in our area, but proceed with caution and test occasionally if you decide to do this, to avoid creating excessively acidic conditions.

Native plants have adapted to our poor local soils in several ways, such as exuding acids from their roots to extract phosphorus and iron despite alkaline conditions. Yet in most cases, even native plants benefit when soils are improved.