Let’s Plant Some Herbs – Selecting Containers, Soil Mixes for Containers

Selecting Containers:

Decorative pots, barrels, and tubs are beautiful and convenient, and there are multitudes of styles. They lend instant color and provide a focal point for space, whether indoors or out. The only tricky thing is getting a sense of how large a pot you’ll need for a particular herb, so check each herb to determine its mature size. For outdoor growing, keep in mind that it’s easier to grow plants in large containers than small ones because large containers hold more soil, which stays moist longer and is less subject to temperature fluctuations. For most herbs, the ideal container provides enough room for the herb to grow in one season. {For example, place a herb purchased in a 4-inch pot into a 6- to 8-inch pot.} Check the herb’s profile to see how big it’s going to get during the season, and use that as your guide.

You should also consider the size and shape of a plant’s root system, how rapidly it grows, and whether it is a perennial, annual, or shrub. It is especially important to check your pots occasionally to make sure the root systems haven’t outgrown their lodgings. Root-bound plants, which have filled up every square inch of the soil available, dry out rapidly and do not grow well.

Of course, the sizes of the containers you use will be limited by the space you have available {especially indoors}, what structures or furniture will support the containers, and whether the containers will need to be moved.

Whichever container you choose, drainage holes are essential. Without drainage, soil can become water-logged and plants will suffer. With the exception of ceramic-type pots, you can always drill drainage holes yourself. There are also self-watering, double-walled containers and pots on the market, and these are ideal for smaller plants that need frequent watering.

When choosing pots for herbs, you also need to take into account the differences between plastic, clay {such as terra-cotta}, glazed ceramic, and wooden pots. Plastic warms up fast {not an advantage outdoors in areas where summers are hot and dry} and thus dries out quickly, but it’s lightweight and inexpensive. Terra-cotta containers can be attractive and inexpensive; they do transpire moisture through their walls, but they also dry more evenly than plastic. You’ll need to protect terra-cotta pots in colder climates because they can crack or break as they freeze and thaw. Glazed ceramic will retain moisture but can keep plants soaked with water if the drainage holes are not adequate. Wood is natural looking in an outdoor setting and can protect roots from rapid temperature extremes. Polyurethane foam pots are gaining in popularity because they resemble terra-cotta pots but are considerably lighter. However, we do not recommend growing your medicinal plants in this type of material because the toxic hydrocarbons emitted by the foam can enter your herb’s roots. There is one thing to remember, no matter which type of pot you choose: Start with small pots when the plants are young and small, allowing for at least one season of growth.

Let’s Plant Herbs:

Once you’ve made decisions about the placement and possibilities of your setting, you’re ready to select soil mixes and plants. Maybe you already know which herbs you would like to grow or you’re inspired to try a new plant.

Soil Mixes for Containers:

A soil mix needs to do two things: hold the plant’s roots in place and retain the nutrients and moisture it needs. As you learn about herbs you would like to grow, you will notice that they differing nutrient and moisture needs. Herbs that originate in four-season climates and the tropics will appreciate rich soils mixes, and desert or Mediterranean plants will respond better to lean soil mixes.

You can create your own soil mix with just a few garden components. Start with a base of whichever you have on hand, either good topsoil or purchased potting soil. Mix the ingredients in a large tub or wheelbarrow, or on a tarp, and then transfer it to your containers.

Rich Soil Mix:

You can purchase all of these ingredients {except the garden soil} at garden or farm supply stores. Coir {shredded coconut hulls} is a great substitute for non-renewable peat, but coir dries out very quickly, so make sure it is moistened before adding it to your mix.

2 parts garden soil or purchased organic potting soil

2 parts compost

2 parts coir, composted fine bark, perlite, or moistened vermiculite*

1 part horticultural sand

Optional: 1 to 2 parts aged manure, for outdoor mixes

  • Reduce by half if you’re using potting soil

Lean Soil Mix:

2 parts garden soil or purchased organic potting soil

2 parts sand, perlite, or vermiculite

Optional: 1 to 2 parts coir or another tilth-building ingredient, such as coffee grounds or peanut or rice hulls

A variety of “soilless” mixes are available. They often contain peat, which is an endangered, nonrenewable resource {although it’s a superior component of soil mixes}. Check before purchasing soil-less mixes, and always buy a certified organic mix unless you trust the source. You can also make your own soil-less mixes.

Rich Soilless Mix:

2 parts coir, moistened

2 parts compost

1 part sand

1 part aged manure or a combination of blood meal, fish meal, bone meal, or seaweed meal

Optional: 1 part perlite or vermiculite

Lean Soilless Mix:

4 parts coir, moistened

2 parts sand

Optional: 1 part perlite or vermiculite

Moisten with fish emulsion, algae, or seaweed liquid {such as Maxicrop}.

Potting Up Herbs:

If you have purchased plants, fill your empty container half full of your soil mix and gently lift a plant out of its nursery pot by cradling the base of the plant stem between two fingers, turning the pot upside down or sideways, then tapping, squeezing, and easing out the plant. Set it in place in the container. Fill the pot with soil mix, making sure that the soil level is at least an inch or two below the rim of the container and the soil is even with, or slightly higher than, the original soil level of the plant. Firm the soil around the plant.

If you’re starting herbs from seed, fill seedling trays, nursery or paper pots, or clean, recycled containers with seed-starting mix, and directly sow seeds into the mix, following the directions for each herb profile.

Caring for Container Plants:

Once you’ve invested time in planting containers, you will want the herbs to grow well and look their best. Follow these tips for great results.

  • Do not place a layer of gravel or broken pottery at the bottom of your container, as many sources recommend. That practice actually worsens bad drainage, instead of improving it.
  • Water container plants thoroughly, but do not over-water! It is sometimes tricky to determine whether more is needed, but you should keep in mind that most herbs in containers should nearly dry out between watering. You can’t always tell by feeling the soil surface whether the soil throughout the container is dry, but you will want to let the plant get {almost} to the point of wilting before you douse it.
  • Container plants need regular feeding. If the herb likes rich soil, water it with a liquid fertilizer every week or two, just until the fertilizer begins to drain out of the bottom. If it thrives in poorer soil, feed it once a month.
  • Remove dead leaves and spent blossoms, and prune back plants that get leggy or stop blooming. Do not be afraid to dig out or remove plants that do not grow well or that succumb to diseases or pests.
  • If the roots of a plant start to emerge from the drainage holes at the bottom of its container, it’s time to repot! Use a pot that is the next size up, fill it halfway with your soil mix, place your plant in the pot, and continue filling until the soil level is a little bit higher than the original soil level of the herb. Firm the soil around the plant. Sprinkle a little bit of compost on the soil surface, then drench it with a diluted fish emulsion, seaweed, or algae fertilizer; you can also apply compost or comfrey tea.
  • Plan to repot your perennial herbs every year. Each spring, remove the entire plant and its soil from the pot and shake off any soil that comes away easily. If no soil comes off easily {or if you see the plant’s roots coiled tightly around the edge of the root-ball}, it’s time for a bigger pot. Trim away any old, dead plant material and gently loosen any visible coiled roots. Put some new soil in the bottom of the pot [or, if you are transplanting into a larger pot, half fill the new container}, set the plant on the soil, and add more soil around the sides of the plant. Then water the new transplant with liquid fertilizer.
  • If your plant is too big to repot, tend and feed it yearly. Using a trowel, break up the surface of the soil and water it with comfrey tea, compost tea, fish emulsion, or other liquid fertilizer. Then apply a fresh layer of compost – as much as possible, while making sure that your soil level remains at least an inch or so below the rim of the container.
  • In autumn, cut back perennial herbs and reduce your watering schedule. Remove the top layer of compost from your pots and replace it. Bring your tender plants inside before the first frost date. You can leave hardy perennials outside, but group them together against a sheltered wall and mulch them. If severe weather is predicted, cover the entire group of pots with a thick layer of straw or leaves, string with non-LED Christmas lights, or use blankets or other protection.
  • Hanging baskets make great herb containers, but be sure to place them in an easy-to-reach spot so they do not suffer from neglect. They are best located where they will not get full sun all day and won’t experience high winds. Creeping herbs, such as Gotu kola and oregano, are the best choices for hanging baskets. Check them every morning and evening to see if they need water.
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