Most farmers and gardeners probably don't enjoy working with clay and limestone soil because it is a tough environment in which to grow crops. Since most plants prefer soils that are fertile and wet, finding crops that will survive in both tough clay soil and alkaline limestone soil can prove to be quite a challenge. Regardless, many people do not have access to ideal growing conditions and must make do with the soil they have available to them, no matter how inhospitable it might be. There are some plants that have proved to grow well in both clay and limestone soil.
Most tubers and root crops don't grow well in clay soils; however, potatoes are tough enough that they can actually break up the clay soil and make room to grow. Since clay soil tends to stay cold throughout the spring, it is better to plant varieties of potatoes that crop in the late summer.
Cabbages are largely an above-ground crop that can be grown in an alkaline environment. For this reason they can be planted in clay and limestone soils because the roots of the plant do not need to burrow deep into the ground in order to obtain nutrients. Another reason that cabbages grow well in clay soils is that they require a lot of water, and many clay soils have water-retaining properties.
Broccoli grows well in clay soils because the clay holds a lot of moisture that is essential for the plant's growth. In addition, Broccoli prefers to grow in a slightly limy environment, so the presence of limestone in the soil can actually act as a catalyst to speed the growth of the crop.
When planting broccoli in clay soils, it is often preferable to choose varieties of the plant that tend to crop later rather than earlier.
Kale is a hardy plant that grows best in a nutrient-rich environment. Since clay soils are often high in nutrients, they tend to support crops of kale quite well, even in the early spring months when the soil is still cool and hard. The only problem is that clay soils typically do not have good drainage. This problem, however, can be rectified by mixing some sharp pieces of gritstone (sedimentary rock consisting of small stones and coarse sand grains) in with the clay in order to improve drainage.
Carrots do relatively well when planted in limestone and clay soils because they can still grow in alkaline environments and they are strong enough to break through some forms of clay. Nevertheless, since carrots are not quite as strong as some of the other root and tuber crops, it would be prudent to check the density of the soil before planting. To test the density of the soil, take a sample in your hand and try to roll it into a ball to see how well it holds together. If the clay is able to clump and form a ball that doesn't easily fall apart, chances are it is a little too dense for planting carrots.