Soil and Pests
Whether outdoor or in a container, good soil is fundamental to the health of your herbs. From the sun, they receive the energy needed to perform all the activities that makes possible growth and reproduction. But that energy is used to drive chemical reactions that can occur only because many of the components originate from the soil.
Water, nitrogen and phosphorus content, alkalinity and acidity, and much more is determined by the nature of the soil used to house and feed your herbs. Keeping all those at the right level is paramount. In container gardening, all that is up to you. In an outdoor garden, nature helps but you may have to give some assistance to achieve optimal results.
Lavender, for example, likes dry, alkaline soil with good drainage. Sage can suffer root rot if the soil is kept too wet.
Soil is categorized as either sandy, clay-like or something in between. Clay particles suspended in the soil readily absorb and retain water. Sandy soil, largely silicates, are more 'glass-like' and hence produce good spacing for air to move around, but water flows through easily.
It's helpful to have a good mix of the two for most herbs. Lean more toward one than the other for those plants that prefer more extreme conditions. Sage likes it dry, but peppermint does better in more moist soil. A good compost will help you achieve the right balance.
There are a variety of pests that can spoil your herbs, just as they do with many other plants. Many fly to the plant, others crawl to it under the surface - another reason to concern yourself with soil maintenance. But herbs can actually help with pest control as well.
Aphids for example, attracted by the odors, love roses and certain vegetables. Planting herbs can actually help deter them. Chives, mint, basil and cilantro can help. Basil, for example, can help deter tomato hornworm from attacking your tomatoes.
But the sword cuts two ways, which way you want to slice will depend on your goals. Dill and yarrow can attract parasitic wasps that feed on the eggs of certain beetles. That helps keep the beetles away, but brings wasps.
At the same time, dill is a 'trap crop' for tomato hornworms. A 'trap crop' is one deliberately used to attract certain species, which then feed on the plant, rather than others you want to preserve. That means, they'll stay away from your tomatoes but eat your dill.
The way out of the dilemma is a judicious use of artificial pesticides tailored to destroy the pests that are attracted to specific herbs. Take care in application, however, if you are growing your herbs for seasoning. Though tested safe, some pesticides can accumulate over time.
Prepare and maintain your soil properly and you'll keep plants healthy and pests at bay.
