The alkalinity or acidity of soil is indicated by its pH, on a scale of 0 to 14 where 7 is neutral. A pH value of less than 7 means the soil is acidic, while a pH in excess of 7 is alkaline. The main problem with alkaline soil is the reduced nutrient and especially micronutrient content available in the soil. A number of fruit trees have adapted to growing in alkaline soils.
Apricot trees are among the fruit trees that can easily be grown in alkaline soils. The trees are well adapted to higher levels of alkalinity and tend to be unaffected by mineral element deficiencies. Apricot trees are long-lived and are also used as small shade trees in landscapes. The trees blossom early and are often susceptible to damage caused by the late spring frosts in many states. Apricot trees produce their full crop of fruit once every five years in the warmer southern regions of the United States and less frequently in the cooler northern areas.
The majority of citrus fruit trees including oranges do best in alkaline soils. Oranges thrive in tropical and subtropical regions of the world and prefer warm and humid weather. When grown in cooler areas, the fruit tends to have a brighter coloured, thicker peel. The navel orange is considered the best-tasting orange for eating fresh. The orange gets its name from the presence of a smaller, secondary fruit at the end of the main orange, which creates a small or large navel-like opening. To maximise cold protection, plant orange trees on the south or southeast sides of a house, and leave enough room for the tree to grow easily.
Pomegranate is a native of Iran, the Himalayas and northern India. Pomegranate trees are 20 to 30 feet in height and very long-lived. The fruit has a thick, leathery skin and is full of juicy, red sacs separated by thin, white membranous walls. Pomegranate trees grow best in the mildly temperate to subtropical regions with cool winters and hot summers. The trees thrive in calcareous, alkaline soils, but are just as well adapted to deep, acidic soils too. Pomegranate seeds easily germinate even on the surface of loose soil. The trees have a low tolerance for temperatures below -11.1 degrees C and are highly drought-tolerant.
- Utah State University Cooperative Extension: Solutions to Soil Problems
- New Mexico State University Extension: Fruit Species and Varieties for Home Orchards
- Texas A&M University Extension: Home Fruit Extension Citrus
- Texas A&M University Extension: Home Fruit Production
- Purdue University Extension: Pomegranate