Growing Herbs in Containers

Pots, planters, and half barrels overflowing with colorful and flavorful herbs add appeal to any garden or home. Growing herbs in containers can serve a variety of practical purposes, as well. If you live in the city and have limited growing space, containers of herbs can turn your balcony into a productive garden. If your yard is shaded, you can locate containers in sunny areas more conducive to plant growth. If you want to grow herbs right outside your kitchen door but your garden is many steps away, containers can solve that problem, too.

Container-grown plants also add versatility to gardens large and small. A pair of matching containers on either side of the front walk can serve as a welcoming decoration, while groups of pots on a deck can provide privacy as well as color, fragrance, and texture. You can position containers on the ground or on a pedestal, mount them on a windowsill, or hang them from your porch. Plant them with a single species, such as rosemary, bay, or thyme, for a stunning garden accent, or experiment by combining herbs of different forms and colors. The possibilities are almost endless.

Choosing Containers

Pots and planters are available in a wide range of sizes, shapes, materials, and styles. You can also modify containers such as bowls, barrels, buckets, wheelbarrows, and wagons to be planters. It’s worth investing in attractive, well-made planters, even if they cost a little more. They will add beauty to your garden’s decor, while inferior planters could detract from it, no matter how appealing the plants they contain.

For the growth and even survival of most plants, bigger pots are better. Those 10-inch hanging baskets — the ones so popular at garden centers in spring — require constant watering in summer. If you go away for the weekend, you’re likely to find a shriveled plant upon your return. But with a larger container and more soil, your herbs can grow a larger root mass that will support lush, healthy, aboveground growth. Larger pots also retain soil moisture longer and are better insulated against temperature fluctuations.

To determine how large and deep a container should be, consider the size and shape of the herbs you wish to grow, as well as the plant types — annuals, perennials, or shrubs — and how rapidly they will grow. Rootbound plants dry out rapidly and won’t grow well. For a mixed planting, choose a planter with enough root space for all of the plants you want to grow.

The maximum size (and weight) of a container will be limited by how much room you have, whether or not you plan to move the container, and the strength of the supporting structure. If your container garden is located on a balcony or deck, be sure to check how much weight the structure will safely hold. If you aren’t sure, contact a structural engineer for an opinion. Remember that a fully watered large clay pot with plants can easily weigh 50 pounds or more.

Whatever container you choose, drainage holes are essential. Without drainage, the soil will become waterlogged, and your plants could die. The holes need not be large, but there should be enough of them to allow excess water to drain out. If a container has no holes, try drilling some yourself (if the container can be drilled). A container without holes is best used as a cachepot, or cover,

Growing herbs in containers

Potted herbs can lend instant color, provide a focal point, or help link the architecture of your house to your garden. to hide a plain pot.

Cachepots (with holes or without them) are useful for managing large plants and heavy pots: Grow your plant in an ordinary nursery pot that fits inside a decorative cachepot so you can move them separately. Self-watering double-walled containers, hanging baskets, and window boxes are also available. These are useful for dealing with smaller plants that need frequent watering.

Containers are made from a variety of materials, and each type has advantages and disadvantages concerning their durability, appearance, weight, and initial cost.

Clay or terra-cotta containers are attractive but breakable and are easily damaged by freezing and thawing. In northern areas, store these pots in a frost-free location to prevent cracking. They are not suitable for hardy perennials or hardy shrubs kept outdoors year-round.

Cast concrete is long lasting and comes in a range of sizes and styles. These can be left outside in all weather and temperatures. You can even make attractive ones yourself. Plain concrete containers are very heavy, so they’re difficult to move and not suitable for use on decks or balconies.

Stone planters provide both durability and beauty, and they come in many different colors and textures. These containers require little maintenance but are very heavy and best used on firm ground.

Plastic, resin, and fiberglass planters are lightweight, relatively inexpensive, and available in many sizes and shapes. Choose sturdy and somewhat flexible containers and avoid thin, stiff ones — they become brittle with cold or age.

Wood is natural looking and protects roots from rapid temperature swings. You can build wooden planters yourself. Choose a naturally rot-resistant wood such as cedar, and never use wood treated with a preservative, which could leach into your soil, enter the roots of your herbs, and ultimately end up in your body. If you’re purchasing a premade container, be sure it was made with untreated wood.

Metal containers are strong, but they conduct heat, exposing roots to rapid temperature fluctuations. Also, metal must be lined with plastic if you’re growing edibles.

Hayrack planters with coir liners are attractive and easy to maintain, and they provide good drainage. They’re great for annuals but not usable for perennials.

Porous terra-cotta pots allow air and moisture to penetrate

Porous terra-cotta pots allow air and moisture to penetrate. This means plants are less likely to drown if overwatered, but they could suffer if you forget to water.

Preparing Containers for Planting

Before you fill and plant your containers, decide where they will be located and move them there. If you plan to move heavy or large pots indoors in fall or to follow the sun during the day, platforms with wheels are available. If you’ll have difficulty watering daily, look for sites that receive morning sun and are shaded during the hottest part of the day, even if you are growing plants that like full sun. Afternoon shade will reduce the amount of moisture your plants need.

Your containers must have drainage holes. If a pot is too deep for a very shallow-rooted plant, you can put a layer of gravel or lightweight packing peanuts in the bottom to reduce the amount of potting soil required.

Plain garden soil is usually too heavy for container plantings. For growing herbs in containers, use a commercial soil mix for houseplants, or make your own lightweight mix. (See the following potting mix recipes.)

Many of the components of potting soil are lightweight, dust-producing materials that can irritate your eyes, skin, and lungs. In some cases, vermiculite — which is in certain soil mixes — has been found to contain low levels of asbestos, and compost and peat moss can contain mold spores. Therefore, when you work with potting soil, observe the following precautions:

  • Work outdoors or in a well-ventilated garage or garden shed.
  • Wear a dust mask and gloves.
  • Dampen individual ingredients before mixing them together to minimize the amount of dust released.
  • After combining the ingredients, add more water to the mix, then stir to ensure that the medium is evenly moist before you fill the containers. After potting, store any leftover mix in a plastic bucket with a lid.
  • If you’ve been working with vermiculite, be aware that the dust can cling to your clothing. Remove and wash dusty clothing as soon as possible to avoid dispersing asbestos inside your house.

Organic Potting Mix

This simple potting mix provides good drainage, air, and nutrients for growing plant roots.

  • 1 part garden soil
  • 1 part well-aged compost
  • 1 part coarse sand or shredded pine or fir bark
  • 1 part perlite (optional)

Enriched Potting Mix

Slow-growing plants, which will remain in the same container for several years, benefit from a mix that contains slow-release organic fertilizers.

  • 1 cubic foot (approximately 32 quarts) Organic Potting Mix (above)
  • 3 ounces bloodmeal
  • 3 ounces soft rock phosphate or colloidal phosphate
  • 3 ounces greensand
  • 2 ounces dolomitic limestone (optional for alkaline-loving plants)

Selecting Plants

Almost any herb — including shrubs and small trees — can grow successfully in a container. Dwarf and compact cultivars are best, especially for smaller pots. Select plants to suit the amount of sun or shade the container will receive.

Use your artistic imagination, and combine upright and trailing plants, colorful foliage, and flowers for pleasure and delight. Grow your favorite combinations of culinary herbs. A “pizza garden” might contain individual plants of thyme, oregano, and basil. A “chili garden” might have several colorful cultivars of hot chile peppers. Container gardens can be enjoyed for one season and composted, to be replanted at the beginning of the next growing season, or they can be designed to last for years.

When designing permanent containers, remember that container plants will be less hardy than usual because their roots are more exposed to fluctuating air temperatures. Nonhardy plants will need outdoor protection or indoor shelter in winter, so consider how heavy the container will be and how you will move it before you plant.

Plant in containers as you would in your garden. If you are planting a mixed container, ignore spacing requirements and plant densely; you’ll need to prune plants once they fill in. Depending on the size of the herb and its type — leafy or with very small leaves; tall or short; spreading or upright; annual, perennial, or shrub — you might need as many as four plants for an 18- or 24-inch container. For trees and shrubs, trim off any circling roots and cover the rootball to the same level as it was set at the nursery. Firm the planting medium gently, and settle it by watering thoroughly. Don’t fill pots all the way to the top with your soil mixture — leave space for watering. And, if you are gardening a few stories up in the air, remember that water follows the rules of gravity.

Caring for Container Plants

Water container plants thoroughly. How often you water depends on many factors, such as weather, plant size, and pot size. Don’t let soil in containers dry out completely, as it is hard to rewet. To keep large containers attractive, spread a layer of mulch as you would in your garden. This will also help retain moisture. Be sure to keep mulch an inch or so away from plant stems and a few inches below the rim of the container.

Container plants need regular feeding, as the limited soil that nurtures the plant also has a limited supply of nutrients. Fertilize plants by watering them with diluted fish emulsion, seaweed extract, or compost tea. Start by feeding once every 2 weeks; adjust the frequency depending on plant response. Be careful not to pour fertilizer directly over the edible leaves of plants you harvest frequently, such as basil. (There’s no need to dress your salad with fertilizer!)

Since containers are focal points outdoors and indoors, give them special attention to keep them looking their best. Remove tattered leaves and deadhead spent flowers. Prune back leggy plants and those that stop blooming. To keep mixed plantings attractive, dig out or cut back any plants that don’t grow well or that go to war with other species, crowding them out aboveground or below-ground. Also keep an eye out for pests such as aphids and mites, and deal with them as soon as possible.

The damage caused by snails and slugs is obvious — holes that cause significant harm to leaves and impede overall plant growth. One way to control snails and slugs is to trap them with a shallow saucer of beer

The damage caused by snails and slugs is obvious — holes that cause significant harm to leaves and impede overall plant growth. One way to control snails and slugs is to trap them with a shallow saucer of beer.

Root Pruning

Root pruning rejuvenates pot-bound plants. Do this every 2 to 3 years for most potted plants; more aggressive growers (such as mints) may require annual root pruning.

STEP 1: To prune the roots of herbs such as mint, first gently remove the plant from its container

STEP 1: To prune the roots of herbs such as mint, first gently remove the plant from its container.

STEP 2: Using a serrated knife, cut each corner from the root base. Do not cut too close to the herb’s main stem

STEP 2: Using a serrated knife, cut each corner from the root base. Do not cut too close to the herb’s main stem.

STEP 3: Use a pair of sharp scissors to neaten any straggling roots. Do not cut too deeply into the rootball

STEP 3: Use a pair of sharp scissors to neaten any straggling roots. Do not cut too deeply into the rootball.

STEP 4: Return the herb to the pot. Snip off older, leggy stems above the soil to encourage new, healthy growth

STEP 4: Return the herb to the pot. Snip off older, leggy stems above the soil to encourage new, healthy growth.