How to Grow, Harvest, and Preserve Culinary Herbs

How to Grow, Harvest, and Preserve Culinary Herbs

  • By Pat Chadwick
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  • March 2021-Vol.7, No.3
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  • 0 Comments

Growing your own herbs is a practical and economical way to produce fresh, nutritious seasonings for the kitchen all year long.  Besides their known health benefits, herbs add flavor, texture, aroma, and visual appeal to many of our favorite foods.  The combination of aromatic basil and sun-ripened tomatoes, for example, is a marriage made in heaven. A few basil leaves tossed into a tomato sauce add a layer of taste and nuance that can elevate the sauce from ordinary to sublime.   The distinctive anise-flavor of tarragon, a common ingredient found in French cuisine, can take green beans to a whole new level of gustatory delight.  The warm, earthy notes of marjoram, paired with lemon and olive oil, make an extraordinary marinade for lamb.  And what would pickles be without dill to give them that extra zing.

In her book entitled Edible Landscaping, Rosalind Creasy defines an herb as “a useful plant whose leaves, blossoms, or stems are used as an ingredient in cooking, dyes, cosmetics, medicine, or a combination of these applications.”   Plainly, with so many possible uses for herbs, there’s a lot that can be said about them.  But for the purposes of this article, the discussion is, of necessity, limited to their culinary aspects.

Before we move on, it’s important to distinguish between an herb and a spice. While both come from plants, herbs come from the green leafy parts of plants, including the leaves, blossoms, and some stems, whereas spices come from the dried bark, roots, buds, seeds, fruits, or berries of tropical plants and trees.

For best success with growing herbs, it helps to know whether the plant is an annual, biennial, or perennial species.

Basil is an example of an annual herb. Photo: Pixabay

Annual herbs, such as basil, chervil, dill, cilantro, fennel, marjoram, and summer savory, complete their entire life cycle in one growing season and then die.  They must be planted each year from seed.

Biennial herbs, such as angelica, caraway, parsley, sage, stevia, and watercress, complete their life cycle in 18 to 24 months. They develop foliage in the first year of growth. In their second year, they develop flowers and set seed, which completes their life cycle.  Like annual herbs, biennial herb species must also be grown from seed.

Chives are an example of a perennial herb. Photo: Pixabay

Perennial herbs, such as chives, mint, oregano, rosemary (moderately hardy in Zone 7), sage, tarragon, thyme, and winter savory, develop their foliage, flowers, and seeds in one growing season and then go dormant for the winter. In spring, they regrow new foliage from their crowns.   Perennial herb species can be grown from seed or propagated from stem cuttings and root divisions.

 

HOW TO GROW HERBS

Most herbs are undemanding in their cultural needs.  Here are some basic guidelines for growing them:

  • Soil – Herbs grow in any good garden soil with a pH between 6.5 and 7.0 – that is, nearly neutral. The soil need not be highly fertile.  In fact, highly fertile soil can produce excessive foliage with poor flavor.  To prepare average soil for planting herbs, incorporate plenty of compost to lighten heavy soil and improve drainage.  Once that’s done, make the planting surface as smooth as possible in preparation for sowing seeds.
  • Drainage – Other than mint, angelica, or lovage, which like fairly moist but well drained soil conditions, few herbs thrive in wet soil. In fact, many of our commonly grown herbs, such as sage, fennel, rosemary, thyme, and winter savory, evolved in drier climates and tend to do well in soil that is allowed to go dry between waterings.  If drainage is a problem, try growing herbs in a raised bed or a container.
  • Sun Light Requirements – Most herbs thrive best in full sun. The oils, which account for an herb’s flavor, are produced in greatest quantities when the plant receives 6 to 8 hours of sunlight per day.   Some herbs, such as cilantro, mint, or tarragon, will tolerate light shade, but their quality and taste will not be as good.
  • When to plant – Sow herb seeds in your garden after the soil warms up in spring and after all danger of frost has passed. If you prefer to start seeds indoors to get a jump on the growing season, sow them in pots or flats in late winter (February/early March) and give the emerging seedlings a sunny window.  As a general rule, sow herb seeds at a depth of twice their diameter. TIP:  Some herbs, such as dill, cilantro, and fennel may not transplant well and should be sown directly in the garden.
  • Pests and Diseases – Fortunately, herbs are not bothered by many insects and diseases. Spider mites sometimes damage herbs in hot, dry weather. Aphids may pose another threat to certain plants, such as dill and fennel, under the right conditions.  A sharp spray of water from a garden hose is generally all that is needed to dislodge your unwelcome visitors to the herb garden.   If you notice caterpillars feasting on your parsley, dill or fennel, they are probably the larvae of Black Swallowtail butterflies.  Just leave the caterpillars alone and plant extra herbs to compensate for any you might lose to this beautiful member of the lepidoptera family.
  • Planting Strategies – Herbs may be planted in a dedicated bed, or they may be interspersed throughout your vegetable garden. But there’s no rule that says you must confine your herbs to the vegetable garden.  Some gardeners enjoy tucking herbs, such as common chives, basil, creeping thyme, or variegated sage, throughout their ornamental gardens, container gardens, or window boxes.  Their blossoms attract pollinator insects, their pungent scents and tastes help deter browsing deer, and the foliage of some herbal species provide exotic contrast and interest.
  • End of Season Care – Guidelines for end of season care vary depending on what type of herbs are being grown. Dead or dying annual herbs should be pulled up and any fallen plant debris cleaned up at the end of the growing season. Most perennial herbs can be cut back to the ground after a freeze.   First-year thyme plants are an exception that should not be cut back.  For more mature thyme plants, cut back about a third of the older, woodier stems by half, which will generate new growth in the spring.   Note:  Rosemary is only moderately hardy in Zone 7.  If in doubt, dig up the plant, re-pot it, and overwinter it indoors.

WHAT TO DO WHEN HERBS BOLT

Bolting is a survival mechanism that some plants activate when they are nearing the end of their life. This process is often triggered by temperatures in summer that are hotter than the plant can comfortably tolerate.  The objective of bolting is to carry on a plant’s genetic line by redirecting energy from leaves to the development of seeds.  When bolting occurs, the plant abruptly elongates, the new foliage may change shape and texture, and the plant stems may become woodier.  For some herbs, bolting alters the taste of the foliage, making it taste bitter and less flavorful.

The good news is that there are several strategies for delaying or preventing bolting and may help prolong the life span of the herb:

  • Harvest herbs frequently. This removes growing points that might otherwise bolt or develop into flowers.
  • Plant herbs in spring or early fall when temperatures are cooler.
  • Mulch around the plant to keep the root zone cooler.
  • If you must fertilize your herbs, apply a fertilizer with a low phosphorus content. Phosphorus triggers flower development.
  • Look for herb selections that have been bred for delayed or slow bolting.

Some herbs, such as basil and mint, develop flowers instead of bolting —  with no impact on flavor. For those herbs, remove the flower buds as soon as you see them developing.  Cut the stem back to just above a set of leaf nodes. The flowers on other herbs such as thyme, marjoram, and oregano are edible but don’t have much flavor. The blossoms on chives do have flavor and are often eaten raw in salads or used for garnishes.       

GROWING HERBS INDOORS

Herbs are wonderfully versatile and resilient.  In addition to thriving outside in the garden, they may be grown indoors or in container gardens on your patio or porch.   Herbs grown indoors require the same conditions as those grown outside.  They need as much sunlight as you can manage to give them and a good quality growing medium that drains well.  If you don’t have a sunny south or west window for your herbs, consider supplementing available light with a grow lamp or fluorescent lights.  Keep in mind that herbs grown indoors are not as productive as ones grown outdoors, but there’s a certain sense of satisfaction to be gained from harvesting herbs from your windowsill on a chilly winter’s day.  To learn more about growing herbs indoors, see Susan Martin’s article entitled Be Inspired with Indoor Herb Gardening in the December 2020 Issue of The Garden Shed.

HOW TO HARVEST HERBS

Although herbs may be harvested at any point during the growing season, for best flavor, harvest when the oils are at their peak.  This is generally when flower buds are just starting to open.  Mints are an exception to this rule.  Their flavor peaks when they are in full flower.

To harvest herbs, cut them after the dew dries on a sunny morning.  This is when the oil content is at maximum.   The harvesting method depends on whether the plant is an annual or a perennial.  To harvest leafy annual herbs, use clean sharp scissors to make a clean cut.  This allows the plant to heal quickly and helps prevent the spread of disease.  Annual herbs can be cut back quite severely.  Make the cut just above a leaf or pair of leaves on stems that are about 4 to 6 inches long.  To harvest a perennial herb, cut only about a third of the top growth or remove just the leafy tips, depending on the herb.

For herbs that are being grown for their seeds, don’t harvest the leaves.  Instead, allow the plant to mature fully and then harvest the seeds once they have matured and turned brown.  Cut the seed heads and place them in a paper bag.  Once the seeds drop off into the bag, spread them out on a drying rack to allow them to dry thoroughly before storing them in airtight containers.

HOW TO PRESERVE AND STORE HERBS

Preserving the herbs you grow yourself is really quite easy, but, if you’re new to the process, it may take a little experimentation to figure out which technique works best for you.  The techniques described below for preserving and storing herbs may take some of the guesswork out of the process.

Methods for Drying Herbs

Herbs being air dried. Photo: Pixabay

Drying is the most common method of preserving the herbal bounty.  However, this method doesn’t work for all herb species because they vary considerably in water content, essential oil levels, and propensity to mold.  For example, delicate leafy green herbs, such as basil, cilantro, chervil, or ferny herbs such as dill and fennel don’t hold up well to being dehydrated. They respond better to freezing rather than drying.   Sturdier, woodier herbs such as bay, oregano, rosemary, sage, and thyme have less moisture in their leaves and tolerate being dried without much loss of flavor.  Keep in mind that dried herbs are generally best if used within a year.

Several drying techniques include the following:

  • Air dry — One of the simplest ways to preserve herbs is to air dry them. This technique has been used for centuries and requires little in the way of supplies or intervention on your part.  All you have to do is tie a bundle of herbs by their stems with string, twine or rubber bands and hang the bundle upside down in a cool, dry place with good air circulation out of the sun until they are completely dry.  Depending on the humidity in the air, the drying process can take from one to several weeks.  To aid the drying process, keep the bundles small.  Also, the bundles tend to shrink as they dry, so check them periodically to make sure they are still securely tied.  Once the herbs are fully dry, remove the leaves and transfer them to airtight containers for storage.

 Another air-drying method involves placing herbs on a clean, food-safe screen or on paper towels on a flat surface. For herbs with small leaves, strip the leaves from the stems after they are completely dry and store them.  For herbs with large leaves, strip the leaves from the stems before air drying them and space them out on the screen or paper towels so that they are not touching. If using paper towels for this air-drying method, they may need to be changed periodically because they can absorb moisture from the drying herbs.

  • Microwave dry – This is the fastest method for drying herbs. Wash the herbs thoroughly in cool water, swishing them around to remove dust, dirt, and other debris.  This is important: pat them completely dry.  Otherwise, they may cook rather than dry in the microwave.  Remove the individual leaves from their stems.  Place the leaves between two paper towels and microwave on full power for 30 seconds.  Check the herbs at that point.  If they are not dry and crisp, turn the leaves over and microwave them for another 30 seconds.  Repeat as necessary until the herbs are completely dry.  Cool the herbs completely before storing them in an airtight container.
  • Dehydrate — If you have a home dehydrator that can be set at a temperature between 95 and 110°F, use it to dry your herbs, especially if you have a large quantity to process. Place the cleaned herbs on the drying trays so that they don’t touch. Dry for about two to four hours.  TIP:  Don’t dry herbs together with fruits or vegetables because the moisture contents are different and also because the flavors may intermingle.

How to Store Dried Herbs

Make sure your herbs have dried completely before you store them. If they are crispy and crumble easily when rubbed between your fingers, they are ready for storage.   Otherwise, any residual moisture may encourage the growth of mold.  Store dried herbs in air-tight containers, such as screw-top glass jars, to preserve their flavors.  Baby food jars are ideal for this purpose as well as saved jars that were previously used to hold herbs and spices.

In general, dried herbs keep well for up to a year.  You may store them whole or crumble them when you pack them in jars.  However, keeping the herbs whole is preferable because they retain their oils and flavor longer.  TIP:  Dried herbs will last longer if you store them in a cool, dry, dark place such as a cabinet or drawer away from heat and light.    

Methods for Freezing Herbs

While drying herbs is the most common method for preserving the summer bounty, freezing them is another favorite preservation method.  It’s fast, easy, and a way to retain much of the taste, aroma, and nutritional value of many herbs.   After harvesting herbs, wash and dry them completely.  At this point, you have several freezing methods, depending on how you plan to use the herbs.  Regardless of which method you choose, frozen herbs should be used within six months for best flavor.

  • Individual leaves – Strip the leaves off the stems, spread them in a single layer on a cookie sheet, and place in the freezer. This allows them to flash freeze without clumping together. Once the leaves are frozen, place them in an airtight container or freezer bag and label and date the container.  If using a freezer bag, remove as much air as possible before sealing it.  This works well for herbs such as basil, chives, oregano, mint or tarragon and allows you to remove as many individual leaves as you need for your recipe.  Just remember that they will be limp once they are defrosted.
  • Whole stems – Just as with individual leaves, freeze whole sprigs in a single layer on a cookie sheet. Then transfer the frozen springs to an airtight container.  Label and date the container (or plastic bag) and store in the freezer for up to six months. This method allows you to remove a sprig at a time and is a good way to preserve hardier herbs such as rosemary, thyme, or sage.
  • Freeze in Water — Some tender herbs can be chopped or left whole, packed into ice cube trays, covered with water and frozen. Once frozen, transfer the cubes to an airtight container for storage in the freezer.  This method works well with basil, cilantro, mint, or parsley and allows you to use single servings of the herb in sauces, soups, stews, or other meals as needed.  TIP:  Think about how you plan to use the herb.  For example, if you place one tablespoon (or whatever measure makes sense to you) of herbs per cube, you will know automatically how much is available when you get ready to use the cubes.
  • Freeze in Oil – Some herbs work well frozen in oil for use in soups, sauces, or other meals for which the oil would normally be used. Basil is a prime example of this method, but other herbs such as oregano or thyme also work well frozen this way.  Combine the fresh herbs with enough olive oil to moisten and pulse in a food processor to blend.  A couple of tablespoons of oil to one cup of herbs is a good ratio but use your judgement to adjust.  Transfer the mixture to an ice cube tray, freeze, and then transfer the frozen cubes to an airtight container for long-term storage.  Another way to do this is to remove leaves from stems, leaving them whole, and then place them in the ice cube tray.  Cover the leaves with oil and freeze.
  • Rolled Herbs – If freezer space is at a premium, here’s a space saver tip for you. Place herbs in a freezer bag and tightly compress them so that they are at the bottom of the bag.  Press out the air, seal the bag, roll the bag around the herbs, secure it with a rubber band and then freeze. Flat leaf herbs such as parsley or sage are good choices for this method.

SUMMARY

If I were to name the most commonly grown culinary herbs, the list would no doubt contain the usual parsley, sage, rosemary and thyme.  But there are so many other choices.  All of them are easy to grow and require little in the way of care.  Herbs can be grown anywhere – in the vegetable garden, in containers on the porch or patio, or on a sunny windowsill in the kitchen.  They can even be tucked among your flowers in the ornamental garden.  Herbs are meant to be harvested regularly. The more you use, the more you get.  And at the end of the growing season, they can be dried or frozen and enjoyed all year long.  Finally, if you’re looking for ideas on how to use culinary herbs, stay tuned —  the April 2021 issue of The Garden Shed features an article on using herbs to flavor food.

SOURCES

The Virginia Commonwealth Unit of The Herb Society of America website https://www.herbsociety.org/

Herb Society of America’s Virginia Commonwealth Unit https://www.herbsociety.org/virginia-commonwealth/

Grow Great Vegetables in Virginia (Wallace, Ira, 2020)

Herbs and Spices (Norman, Jill, 2002)

Homegrown Herbs (Hartung, Tammi, 2011)

Vegetable Gardening in the Southeast (Wallace, Ira, 2013)

“Drying Herbs,” Perdue University Extension website

Care of Herbs,“ University of Maryland Extension Home and Garden Information Center

“Growing Herbs,” Perdue University Extension Publication HO-28.

‘Herb Culture and Use,” Virginia Cooperative Extension Publication 426-420, authored by Shawn Appling and Joyce Latimer.

“Let’s Preserve:  Drying Herbs,” Pennsylvania State University Extension website, (www.extension.psu.edu)

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