Beautiful, delicious, aromatic and self-sufficient, herbs represent a form of perfection in the garden.
Culinary herbs are singularly suited to growing in pots and other containers -- they love a dry, airy perch. People love them, too: 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.
May is the month for assembling your herbs. The weather is warm enough, finally, to please heat seekers, such as basil and lemongrass, and to coax mint into life for Kentucky Derby juleps.
Here's how to do it:
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. Forms, colors and materials vary widely.
If you are on a budget, a simple plastic or basic clay pot costing a few dollars will work. If you have deeper pockets and 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 as much as $200 or more. Metal containers can look stylish, but they can get uncomfortably 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.
No potted plant will thrive in poor, dense 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. You can make your own or buy bags that are ready-made. 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. Adding sand might not help so much.
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." The same principle applies to potted herb gardens.
We asked Adam Pyle, horticulturist at the U.S. Botanic Garden, for some of his favorite herb combinations:
• 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. 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 are 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. Most herbs are short-lived, 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. This will protect the pot from freeze damage and nurture the herbs.
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.