Growing herbs in a container

Washington PostJune 7, 2013 

  • Potted herbs

    A 14-inch-diameter pot is the optimal size for a collection of herbs – large enough to do the job without becoming a major production in weight, cost and soil volume.

    Herbs need great drainage – some gardeners place clay shards over the drainage hole. Others line the pot with landscape filter fabric to keep soil from washing out.

    Broad, bowl-shaped containers hold moisture longer than regular pots and may drown herbs.

    Glazed ceramic, concrete and resin pots tend to be freeze-resistant and can be left outside in the winter, but they should be protected against saturation. Most terra cotta pots are not frost-proof and should be brought into a sheltered, dry location in winter.

    Many independent garden centers carry a large selection of attractive glazed and clay pots, many of them mass-produced in Southeast Asia. High-design resin and concrete pots are available from companies such as Campania International, Lunaform and NativeCast.

Beautiful, delicious, aromatic and self-sufficient, herbs represent a form of perfection in the garden.

They are singularly suited to growing in containers. They love a dry, airy perch. You can position a potted herb garden almost anywhere with a bit of sunlight – on a breezeway, a balcony, a front stoop or a back patio. The only criterion, other than sunlight, is that it be handy, so you can snip what you need for the kitchen. Herbs love to be trimmed; they respond by growing bushier.

Even if the cool spring prompted you to delay your garden, it’s not too late to start a crop of herbs in pots. The weather is warm enough, finally, to please heat seekers, such as basil, lemongrass and mint. Here’s how to grow your own:

Containers

The larger the container, the better. A greater volume of soil moderates root temperatures, retains moisture and allows room for crowded herbs to grow. A 14-inch-diameter pot is ideal for housing four to six herbs. Don’t go with anything smaller.

A simple plastic or basic clay pot costing a few dollars will work. If you want to make more of a design statement, you can find glazed ceramic pots for about $30 to $60, smart terra cotta pots from $40 to $100, and high-design concrete or resin pots for $200 or more. Metal containers can look stylish, but they can get too hot in summer, as can black or dark-hued pottery.

All pots must drain freely, so make sure they have at least one drainage hole. Decorative “feet” – three to a pot – are cheap and can make a vital difference in preventing waterlogged roots, especially if the pot sits directly on concrete or stone paving.

A grouping of pots can provide a focal point and expand your range of herbs, but avoid lots of little pots. Three beefy pots of different diameters and heights can look great, define a corner of a patio, or visually lighten corners and walls.

Soil

Don’t use garden soil or stuff left over from last year’s pots. The classic general purpose potting soil is a peat-based mixture with perlite and limestone, often with compost and vermiculite added. For herbs, particularly Mediterranean herbs such as rosemary and lavender, some gardeners like to add some gravel or chicken grit to the mix to aid drainage.

Planting combinations

In creating any effective container garden, the pros give plants three distinct roles: as an upright accent, as a lower-growing mound and as a trailing plant. They are known in the trade as “thrillers, fillers and spillers.” Adam Pyle, horticulturist at the U.S. Botanic Garden, shares some of his favorite herb combinations:

Decorative Mediterranean: In a stylish square-topped clay planter, he placed four plants: an upright rosemary, rue, a silver-leafed curry plant ( Helichrysum italicum) and a variety of oregano named Kent Beauty.

Floral twist: In a blue glazed pot, Pyle assembled a lot of curly parsley, which flopped and functioned as both filler and spiller. For height he used the feathery bronze fennel alongside a small-leafed and variegated form of basil named Pesto Perpetuo. To provide some visual punch, he added two annuals with edible blooms: nasturtium (whose peppery leaves also spice up a salad) and a common marigold. Another group of marigolds, called Signet marigolds, have finer leaves and flowers and are well suited to the herb container.

Standard herb combo: In a green ceramic pot, Pyle selected five herbs that tolerate moisture with adequate drainage. As a thriller, he put in a small bell pepper plant. His was unnamed, but I suggest a diminutive and fruitful sweet bell pepper named Golden Baby Belle. He added dill (variety Bouquet), which is a cool-season herb. Once it flags in the heat of early summer, you could replace it with a scented geranium. He added a red-leafed basil variety and a nasturtium from a group called Alaska, which is more heat-tolerant than other nasturtiums. He finished the ensemble with a trailing common oregano named Hot and Spicy.

Culinary Mediterranean: Pyle likes to put dry-loving Mediterranean herbs in clay pots, which are porous and wick moisture from the soil more rapidly than other types of containers. He also adds extra drainage by placing gravel or other small stones at the base of the pot, incorporating chicken grit into the soil and topping it off with a mulch of small pebbles. You could use washed pea gravel. Pyle employs an expanded glass product named Growstone.

In this recipe, he used rue (not used much as a culinary herb, but with a lovely blue-green fine texture), a novel variety of chives named Cha-Cha, silver santolina, the English lavender Hidcote, compact with indigo blooms, and a caraway-scented thyme, noted for its caraway flavor, fine texture and rot resistance.

Perennial herb combo: This is my recipe for herbs that are winter-hardy and will give several years of service. It’s worth noting that most herbs are short-lived plants, especially in pots, and should be replaced after three years or so. Plant these in a frost-resistant container (not standard terra cotta) and remember to move the pot to a sheltered location in the winter. I have suggested five herbs: The twist is to use rosemary as the spiller by selecting a trailing type such as Prostratus. For the thriller, use a lavender – English or French lavandin type – and fill in with hardy sweet marjoram and lemon thyme, the latter a yellow variegated thyme with citrusy oils. Finish the medley with a clump of chives.

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