Routine care in the herb garden

The majority of herbs are easy to grow organically, requiring only a modest amount of maintenance to keep them healthy and disease free. Much of the effort associated with common herbs is expended to ensure they remain confined within a reasonable space and do not spread uncontrolled like weeds. Mint, nettle, nasturtium and others will quickly dominate the garden, choking out rival plants when unattended. Containment strategies must address the method of reproduction. Herbs like nasturtium and nettle multiply rapidly through seed scattering unless the heads are removed early enough to prevent this. A single specimen of Vietnamese mint is capable of releasing multiple root runners every season. Once these runners extend past the plants designated boundaries, they will need to be extracted like difficult weeds. Mulching may help control their numbers although a better alternative is to grow these varieties in pots where their tendency to distribute root runners can be continually checked. Horseradish is another species capable of disrupting a garden. The golden rule insists that horseradish must be completely removed from the garden every second year before being replanted on a smaller scale.

Unless picked regularly, fast growing herbs like marjoram, mint, and lemon balm must be cut back and shaped to maintain fresh green growth and avoid coarseness. An occasional pruning keeps plants compact, improves their appearance, and prevents unwanted seeding. Pruning also provides an opportunity to deal with the weeds and grasses which grow naturally amidst spreading herbs. When it is too difficult to tackle these with a trowel or handfork, perennial weeds can be cut back to ground level. Shears are suitable for trimming small flowering plants like chives, and chamomile, while secateurs are the best tool for trimming thicker stems of rosemary, bay, and lavender. By removing their flower buds, several of the culinary herbs will concentrate additional oils and flavour in their stems and leaves. This applies to thyme, chicory, oregano, rosemary, and sage.

Unless pruned low at the beginning of spring, fennel and hyssop are likely to become extremely coarse in stem and leaf. When necessary, herbs can be encouraged to grow compact and bushy by progressively pinching out their central growing tips.  Other tall growing species, like marshmallow, are selectively pruned by removing leaves spreading around their base. Very tall and slender specimens may also require the additional support of a wall or trellis. From an organic perspective, clippings from healthy plants can always be put to good use by recycling them as compost. Valuable culinary herbs can be dried or blended in sauces and preserves. Lavender flowers can also be dried or included as an ingredient in home made organic soap, perfume, and hair products.  

In general, organically grown herbs are less likely to suffer pest and disease problems than other cultivated plants. Some of their resilience is attributed to the natural aromatic properties and oils which appear to discourage harmful microbes and insects. This depends upon the provision of suitable growing conditions since even the toughest varieties of herb can weaken when planted in the wrong soils, or exposed to unaccustomed climates.

With a few exceptions, herbs prefer lean, well drained soils with a neutral or slightly alkaline pH. The varieties originating from Asian, African, and Mediterranean regions tend to require a lot of sunlight while Northern European herbs often prefer indirect sun and shade. It is good practice to routinely inspect herbs, ensuring optimum garden conditions and to identify early signs of problems, should they occur. Look for signs of stunted growth, damaged or irregular growth shoots, and yellowing or off colour foliage. In most cases, minor fungal outbreaks should be treated by removing the affected foliage and improving soil drainage by the inclusion of leaf mould or similar organic materials.

Aphids will occasionally infest mint, hops, nasturtium, and arnica. These can be controlled by rinsing each plant with a mild, biodegradable soap solution and encouraging beneficial predators like ladybird and lacewing. Scale or mite infestation should be wiped away with a sponge or cloth soaked in methylated or surgical spirits. Caterpillars, snails, and slugs are often attracted to herb seedlings, particularly mustard, cress, and sage. These can be removed by hand or captured in funnel traps.
 
While mulching is not often associated with organic herb cultivation, there are several advantages which should be considered. Water is an increasingly valuable commodity which must be conserved wherever possible. According to data included in the Denniford report on organic viticulture, mulching decreases total water requirements by approximately forty percent in temperate climates, rising to nearly sixty percent for dry and semi-arid regions. Compared to vegetable and vine crops, most herbs have modest water requirements, although overall volumes and savings will be significant for intensive organic operations, particularly those spread over large areas.

Mulching is also used to control grass and weeds which can become a seasonal problem for both hobbyists and commercial organic producers. It only makes sense to use high quality mulches such as organic pea straw, compost, untreated sawdust, and finely chopped twigs, leaves, and bark. All of these materials can be mixed together however it is better to avoid the use of plastic polythene sheets since these trap water and compromise efficient air circulation around the roots.

With the exception of a few tropical and sub-tropical varieties like basil, ginger, lemongrass and coriander, most herbs prefer lean, slightly alkaline soils. Fertilisers and liquid plant foods can have a dramatic impact on delicate culinary herbs like tarragon, oregano, and marjoram. Frequent or heavy applications tend to encourage rapid flourishing of bright new growth which, according to connoisseurs, coincides with a marked decrease in aromatic potency and flavour. A better option is to use recycled organic materials such as garden compost, leaf mould, and seaweed. These can be incorporated lightly into the soil or applied more generously as surface mulch.

In addition to the tropical and sub-tropical herbs mentioned earlier, garlic, chives, mint, bay, and hops will benefit from this approach while aloe, anise, rosemary, thyme, and sage will not. With the exception of hops and mint, these herbs will slow their growth during winter. In cooler climates, the outdoor growing season for basil and coriander can be extended into autumn with the use of insulated cloches.