A specially constructed spiral herb bed provides a suitable habit for Mediterranean plants, which can be hard to grow in our wet weather and clay soils.
The rain in Spain may stay mainly in the plains, but it only falls in winter. Dubbed "Mediterranean Climate," this weather pattern is characterized by mild wet winters and dry, not necessarily hot, summers. It is caused by oceanic high pressure belts called "anticyclones." These are found on the western coasts of South Africa, South America, California and Australia as well as the Mediterranean Basin.
Plants native to these places have various adaptive strategies including summer dormancy. Others conserve water within woody stems and needle-like leaves. Some bloom in late winter so that seedlings become established before the long dry season begins. Their native soils are "lean"--i.e. low in nutrients like nitrogen--rocky and a bit alkaline. They struggle with our acidic clay soils, humidity and generous precipitation. Some of our favorite herbs are among these plants, including lavender, sage, rosemary and thyme.
Success in growing Mediterranean natives here requires creation of a special environment. An option for growing herbs with a range of requirements is an herb spiral. This structure is about two yards in diameter and one yard tall. It can be made of brick or stone. Choose a sunny site where water does not pool. As in this illustration, lay cardboard or old carpet over the area to prevent weeds from growing between the bricks. Fill the core of the spiral with small rocks and coarse sand to ensure drainage. Top this area with cactus-mix potting soil. In the lower areas use ordinary potting soil.
The very top of the spiral is warm and dry, a perfect spot for lavender and rosemary. Place sage, thyme, and oregano along the upper coil. Basil, parsley and chives will be happy in the mid level. Moisture-loving mints find a home at the base. Water every seven to 10 days depending on rainfall. The moisture lovers may need more frequent watering during hot, dry periods.
The high-and-dry perennials should survive a typical winter here. Resist cutting them back in the fall. Prune and shape the woody sub-shrubs in spring when growth resumes. I have killed lavender with a bad haircut.
Containers offer a smaller-scale solution. The container needs to be large enough to accommodate the root system of the mature perennial. I set mine on bricks or pavers to ensure that they are never sitting in standing water. Use cactus potting mix, and mulch with gravel. Water weekly if there is no rain.
Herbs in containers need some winter protection from wind. Placing a barrier of straw bales or moving them close to the house should be enough. Resist bringing them indoors where they may not survive the reduced light levels.
The small woody aromatic herbs from the Mediterranean region are a bit of a challenge to grow here, but try the above remedies and you may previal. The techniques discussed in this article would also work for growing hummingbird mint (agastache) which attracts pollinating insects and butterflies as well as hummingbirds.
Master gardener Ann Bartlett never lets lack of familiarity with a plant stop her from trying it in the ornamental gardens around her home.