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University of Illinois Extension
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Growing Herbs in the Home Garden

James C. Schmidt
Extension Specialist, Home Horticulture/4-H
University of Illinois Extension

Little wonder that herbs have earned a place in American gardens.  Freshly harvested herbs have pungent and aromatic qualities that far exceed those of their commercially obtained counterparts – whether fresh or dried.  Even after the outdoor growing season is over, you can still enjoy dried herbs in fragrant potpourris and sachets.  You can also grow herbs indoors in pots on sunny windowsills, and use them for culinary purposes, whether fresh, dried, or frozen.  You will enjoy growing herbs because their culture is easy.  They require little care and space, have very few insect and disease problems, and generally require only moderate fertility levels.  Above all, herbs provide you with a continuing and satisfying hobby. 

CHOOSING A SITE

Herbs flourish under the same conditions that you provide for your flower or vegetable garden.  Although most herbs will grow in partial shade, it is better if the herb garden receives at least 4 to 6 hours of sunlight a day.  A majority of herbs will grow well under a wide range of soil conditions, with the exception of extremely wet, poorly drained soils.  Note, however, that sage, rosemary, and thyme require a well-drained but moderately moist soil.

If the garden soil is poorly drained, you can improve the situation by modifying or amending it.  Even more effective would be the use of raised beds.  To improve soil fertility and tilth, add several bushels of compost per 100 square feet of soil before planting.  Spade it into the soil thoroughly.  

In general, herbs do better in soils of low to medium fertility, so additional fertilizer applications are not needed.  Soils with high fertility tend to produce lots of foliage that is low in flavor.

Prepare your garden site in the same manner that you would a vegetable garden, spading it to a depth of 6 to 12 inches.  Then level and rake the site to remove any large clods and debris.

FITTING HERBS INTO YOUR LANDSCAPE

Decide on a type of garden.  An herb garden can take any form.  They can be planted in a formal garden; informally with flowers; trees, and shrubs; or in theme gardens.

A formal herb garden generally is composed of a series of beds that are not necessarily identical but appear balanced.  The herbs are arranged by height, foliage color, and/or use, often in rows.  Wide walkways are used to separate the beds and give the garden a sense of spaciousness.  Formal gardens of the 16th century were designed as knot gardens.  This style used plants to create intricate, geometric designs within a square or rectangle.  The designs were often edged with low-growing hedges of lavender or boxwood that showed off the subtle characteristics of the herbs. When choosing plants for a knot garden, select those that are compact, low-growing, and are manageable.  Some suggested herbs are thyme, germander, rue, hyssop, rosemary, and santolina.  Avoid invasive herbs such as the mints.  In addition to the herbs, statuary, topiaries, and container-grown plants are important features to include in a formal garden.

Herbs are typically planted in a garden alone.  Unfortunately, most herbs look great in May and June, and then get scraggly and unattractive the rest of the season.  For this reason, they are often informally combined with annual and perennial flowers, trees, shrubs, groundcovers, vegetables, or other plant material.  This allows you to take advantage of the various colors, textures, sizes, and shapes that other plants have to offer.  

Some gardeners prefer to select a specific theme for their herb garden and choose herbs accordingly.  Some examples are a kitchen garden (including thyme, sage, basil, tarragon, dill); a single color garden such as gray-green (including horehound, lavender, artemisia, and wormwood); a scented garden (including mint, scented geranium, lemon balm, silver thyme, and rosemary) or a garden with different varieties of specific herb (common sage, tricolor sage, golden sage, purple sage, clary sage, pineapple sage).  The possibilities are limited only by your imagination. 

Don’t limit your use of herbs to specific situations.  You can use them to enhance most any garden.  Of course, some grow better as groundcovers, others as edging plants; still others are best when intermingled with different plants in a mixed border.  Most, however, are best used where their fragrance and beauty can be appreciated upclose.

Put your ideas on paper.  Once you have decided on the type of garden you want, make a rough sketch or drawing on paper.  This helps to visualize what the garden will look like and will help in figuring the number of plants needed.  Think about the staging (shorter plants in front, taller towards the back) as well as succession of flowering.  Consider the specific requirements of the herb (sun vs. shade, moist vs. dry soil).  It is much easier having it on paper than trying to remember it. 

Consider color schemes and combinations.  Use specific plant characteristics when deciding where to locate the plants.  Color is one of the most noticeable features of a plant.  By choosing a single color scheme, you can create a garden that gives a sense of space, openness, and brightness.  For greatest effect, vary the height, shape, texture, and size of the flowers and tones of the color.  Colors can also be used in combination; some colors blend together better than others.  For example, a silver-foliaged plant such as horehound enhances red or pastel foliage or flowers. 

Contrast is another technique to use to make your garden more interesting.  By definition, contrast is using opposing elements close together to produce an intense or intriguing effect.  You can contrast textures, dark or light colors, shapes, lines, flower form, flower height…any design element.  For example, rounded plant forms look best next to those that are upright; round flowers complement a plant with spiky flowers.

Keep the plants together.   It is very important to define the garden.  The plants will look better if kept together rather than scattered through the lawn.  Edging the herb garden defines the planting area and makes the garden look as though it belongs in the landscape.  If the plants are located next to a wall, a sidewalk or path can provide the boundary.  If they are located in a lawn area, a permanent edging of brick or wood can be useful.  A defined area looks more “finished” and is easier to maintain.

Create a unified effect.  In addition to plant material, hardscapes such as benches, sculptures, birdbaths, and other objects serve as focal points and enhance the plantings.  

GROWING HERBS IN CONTAINERS

Many herbs can be grown successfully in containers on a patio, balcony, or terrace.  There are many reasons why you may want to grow herbs in containers rather than in a garden.  First, many of them are small and tend to get lost in a landscape.  Growing them in containers brings them closer to the viewer.  This is especially true of ornamental herbs that have unique qualities that should be viewed upclose.  Container growing is especially recommended for herbs that require good drainage and tend to rot in overly wet garden soils, or for tender herbs that need to be over-wintered indoors.  Containers are easily transported and can be arranged in attractive groupings with containers of flowering plants.

Choosing a container
Any container is suitable for growing herbs as long as it has a drainage hole.  Clay pots are often preferred because they are more porous than plastic and complement the plants.  Other containers that work well include window boxes, strawberry jars, and hanging baskets.

Soil mix
The soil you use should be loose and well-drained.  Purchase a pre-packaged potting mix or make your own by combining equal parts potting soil, peat moss, and perlite (or vermiculite).  

Choosing the plants
Small and low-growing herbs look best in containers.  Some examples are variegated sage, purple sage, golden sage, parsley, Greek oregano, rosemary, prostrate rosemary, marjoram, bush basil, thyme, chives, and summer savory.  Most containers can accommodate a combination of several herbs and flowers.

Care of herbs in containers
Watering is the most difficult part of container gardening.  Plants growing in containers dry out faster than those in the ground.  On a hot, sunny day, a container may require water once or twice daily.  Of course, the water requirements vary from plant to plant.  When the top of the soil feels dry, apply enough water to allow a small amount to come out the drainage holds in the bottom of the container.  Since most herbs do not require high fertility, you should not need to fertilize them as much as you would other container-grown plants such as flowers or houseplants.  During the growing season, pinch the plants back to keep them bushy and compact and remove any dead or diseased leaves to keep them healthy.

Growing herbs indoors
Herbs growing in containers can be easily moved indoors for the winter.  Before doing so, the plants should be acclimatized early in the fall.  Gradually move them indoors for a few hours at a time over a period of several days so they get adjusted to the differences in temperature and light.  Herbs growing indoors should be treated differently than those out-of-doors.  One of the biggest problems is providing sufficient light to keep the plants from getting spindly.  Grow them in the sunniest location you have or under fluorescent lights.  Since the plants will not be using as much water as they did outdoors, water only when the soil is dry (an exception to this is rosemary, which needs to be kept moist).  Apply enough water so that some drains out the bottom of the pot.  Avoid over-watering, which causes the roots to rot.  Check the plants frequently for aphids, spider mites, and whiteflies, which are common pests on herbs grown indoors.  If you find an infestation, treat immediately.

AVAILABILITY OF SEEDS AND PLANTS

Seeds and plants of various herbs can be obtained from mail order companies that specialize in herbs, or you can often find a fairly good selection at local seed and nursery firms.  The seeds of more common herbs such as dill, basil, and parsley are usually available from local seed dealers and garden centers, while the less common ones should be purchased from companies specializing in herbs.  

CLASSIFICATION OF HERBS

Herbs are classified either as annuals, biennials, or perennials.  Annual herbs are usually grown from seed; they grow, flower, and produce seed during one season, and then die.  Biennial herbs grow for two seasons, flowering the second year only.  Perennial herbs, once established, over-winter and flower each season.  Some herbs are tender perennials; these do not survive severe winters and are best grown as annuals or over-wintered indoors.

SUMMER CARE OF THE HERB GARDEN

Your herb garden will need attention throughout the growing season.  Weed control and provision for adequate moisture are two important cultural necessities.  When rainfall is less than 1 inch per week, provide additional moisture.  The use of mulch is an attractive and effective means of controlling weeds and maintaining constant soil moisture and temperature for the root systems of your herbs.  Mulches that you might consider include bark chips or shredded bark, compost, ground corncobs, pecan hulls, or dried grass clippings.  To be effective, the mulch should be applied at least 3 inches deep around the plants. 

WINTER PROTECTION

Most perennial herbs are hardy plants that are able to survive winter.  However, in Illinois, winter weather can be severe.  Sometimes herb plants succumb to the extreme temperatures but often extreme temperature fluctuations as well as extremely poorly drained sites kill them.  Here are some suggestions to ensure plant survival.

First, start out with healthy plants and maintain vigor throughout the growing season.  Though some herbs tolerate poor or wet soils, the majority prefers to grow in well-drained soils.  Plants in overly wet soils will grow poorly and are subject to root rots.  Soils that are heavy should be amended with organic matter to loosen the clay structure.  Another method of improving drainage is to plant the herbs in raised beds. 

Avoid late fertilizing and pruning.  Most herbs are more flavorful when the fertility is not too high.  Pruning should be done during spring and summer; avoid excessively cutting the plants back in the fall.  The growth serves to catch leaves that help insulate the plants.  Additional mulch of evergreen branches or some other material should be placed around the plants.  Avoid mulch that packs down and stays too wet during the winter, which would cause the plants to rot. 

Finally, plants that are marginally hardy (such as rosemary and Greek oregano) should be dug up, potted, and over-wintered indoors.  They can be moved back to the garden the following spring.