Harvest and storage methods are critical components of utilizing herbs or other plant material for culinary or medicinal purposes. Gathering, drying and storing herbs correctly can make a considerable difference in the quality and quantity of essential oils and other chemical constituents in the herb, affecting their flavor, shelf-life and medicinal potential.
Most leafy herbs are at their peak of essential oil production during the flowering period. Ideally, leaves of these herbs should be collected just before the buds begin to break, unless you wish to harvest the flowers themselves, in which case, the entire stem can be taken when most of the flowers have opened or begun to open. Some herbs, such as tarragon, don’t always bloom. In these cases, you can learn to time the harvest through smell and taste, or sync the harvest with another heat-loving herb, such as rosemary or sage. In any case, it is best to collect herbs in the morning after the dew has dried but before the day becomes hot, because when the temperature rises the volatile oils in the leaf’s surface will begin to dissipate.
Sometimes slightly stressing herbs prior to harvest will trigger a kind of survival mechanism within the plant that increases the concentration of volatile oils and medicinal compounds in the leaves and flowers. Withholding water from a plant for a few days before harvest is one way to stress a plant but this technique can not only be tricky, but fatal to the plant. It’s very important to know how much stress the herb can handle before it begins to cause real damage, so play it safe and never deprive herbs of water for more than five days during the hottest summer months.
If you are of the habit of fertilizing your herbs, you might consider this: Most herbs are naturally adapted to growing on lean soil and don’t generally require fertilization to produce good growth and quality flavor. In fact, when an herb’s growth is over stimulated by fertilizers, the plant tends to put more energy into growing new leaves and stems and less into volatile oil production, resulting in a milder, if not bland, flavor. The lesson here is that if you fertilize your herbs, do so very lightly. And if they seem to be bland or unflavorful, you may need to stress your plant by withholding feedings for a month or more or be prepared to cut the plant back to encourage new, more flavorful growth.
To begin, it is important to be on the same page when we talk about “harvesting”, “cutting” and “trimming” – all of which can mean very different things to different people. For this article, cutting and herb “hard” means to remove stems to within 4”-6” inches of the crown of the plant. And just to clarify things, a good rule of thumb when cutting any herb is to remove no more than two-thirds of the length of the stems at any one time. Also, when cutting herbs, always use a very sharp pair of scissors or clippers, cut each stem just above a pair of leaves, and water the plant well after each harvest.
Before you cut anything off of your herbs it is important to note the difference between annual, perennial and biennial herbs. Annuals are plants that grow leaves, set seed and die each year. Basil, dill and cilantro (coriander) are examples of annuals. Perennials are herbs that grow leaves, set seed, go dormant and them reemerge from the same rootstock year after year. Perennials include sage, thyme and rosemary. Biennials are plants that grow foliage and die back to rootstock in the first year and reemerge, fruit and die completely the second year. Examples of biennials include parsley and caraway. And last but not least are perennials that are treated like annuals, such as parsley. Because while parsley is truly a perennial, its leaves become bitter in the second year of growth. So unless you want parsley seeds for medicinal or seed saving purposes, you’ll want to start fresh plants each year.
Since annuals grow to their full potential in one season, they are generally cut hard during the main harvest season. And depending on the climate, they might still have enough energy to put on more usable growth by fall. Perennials on the other hand, tend to spend their first year or two in the garden establishing their rootstock and often don’t grow very large. For young herb plants, it is better to take several small trimmings or selective stem cuttings during the season rather than a large hard cutting all at once. On the other hand, most mature perennial herbs can withstand either one hard cutting each year, or at least tow smaller cuttings in which half of the stems are taken, depending on the vigor of the herb and the length of the growing season. It is always best not to cut woody perennials hard to the ground all at once, as this may slow their overall growth and reduce their winter hardiness.
Of course, not all herbs are grown for their leaves. Some leafy annual herbs such as garlic, onions, dill and anise are grown primarily for their seeds or bulbs. In cases like these, it is best to remove as little foliage as possible to allow the plant to put all of its energy into producing fruit or seed instead of making a lot of new leaves. However, taking a few leaves now and then generally doesn’t hurt overall production. One notable exception to this rule is cilantro, which is grown both for its leaf and its fruit. If carefully timed, two separate harvests can be had – the first for its flavorful leaves and the second for the pungent fruit. To try this, pinch the tips off of young plants once when they are 5”-6” tall and again in two weeks. Just as the plant begins to form flowers, cut the stems to within 4” of the soil and harvest the leaves. Allow the plants to mature and produce seed. Using this method you not only get a second harvest of leaves, but an abundance of coriander seed as well.
Don’t Forget the Flowers
The flowers of many herbs are more than just lovely; they are downright tasty, too. Flowers make wonderful edible garnishes in salads, drinks and other dishes and those of anise and sweet Cicely can be candied for a flavorful sweet treat. Many herb flowers are added to oil or vinegar to impart wonderful flavor and beauty to the finished product. And, of course, flowers are medicinal and can be added to teas and infusions.
Flowers retain their flavor and beauty better when they are collected in the morning before the dew had dried and the day becomes hot. If the flowers are to be held for a meal later in the day they should be cut with a bit of stem attached and kept in a jar of water in the refrigerator until needed. Otherwise they should be used as soon as possible or either frozen or dried.
Single flowers or clusters of flowers that open all at once are best gathered immediately after they open to capture their fresh appearance and aroma. It is also important to remove flowers quickly from herbs that are being grown for bulbs, roots or rhizomes so that the plant will put all of its energy into producing those and not the seeds. Of course, if seeds are what you’re after it is better to take as few flowers as possible.
Flower spikes and clusters of intermittently blooming flowers are harvested when at least half of the blossoms open. Allowing most of the flowers to open makes for a prettier display and adds a bit more color and flavor to teas and oil infusions. But waiting until herbs begin to bloom to take the main leaf harvest doesn’t hurt the overall flavor or medicinal value of the leaves all that much and may actually save you time in the long run.
See you in the garden!
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