Tarragon

Identification and origin

Artemisia dracunculus belongs to the aster family, Asteraceae. Its natural range is huge: it covers much of eastern Europe and Russia, Central Asia, Siberia, Mongolia, China, the Himalaya, Iran and Turkey, as well as western and central North America, from the Yukon to Mexico. In the wild it grows in dry, open places.

It is a herbaceous perennial with a somewhat woody base and upright, branching stems, spreading slowly by creeping roots. It usually grows 12 in – 3 ft tall. The narrow, lance-shaped leaves are 1–3 in long and 0–0 in wide and strongly aromatic. In summer, small rounded flower heads, pale yellow to greenish yellow, appear in branched clusters.

For cooking, it pays to tell apart two types, both of which belong to the species:

• French tarragon (‘Sativa’) is a slender plant 20 in – 2.5 ft tall, with dark green, narrow, slightly twisted leaves and a strong anise and licorice flavor. It rarely blooms and its flowers are sterile, so it sets no seed.
• Russian tarragon is much more vigorous, reaches about 3.5 ft, and handles cold and wet better, but its flavor is grassier and slightly bitter. Seed sold as “tarragon” is almost always this type.

Buy plants in person and crush a leaf before you choose.

Light

Tarragon wants full sun, at least six hours of direct light a day, in a warm, sheltered spot facing south or west. It tolerates light shade, and where summers regularly top 90 °F, a little afternoon shade improves survival.

Indoors it only thrives in a very bright south-facing window or under grow lights running twelve to sixteen hours a day. A plant short on light gets leggy, makes small leaves and loses its aroma; even well lit, it is less flavorful than one grown outdoors.

Watering

Let the soil dry between waterings: too much water is the main cause of failure. Water a new planting regularly until it is established; after that, in the ground, tarragon handles drought well. Its roots stay shallow, so a layer of mulch helps keep a little moisture near the surface.

In a pot the mix dries quickly in summer: check it often with a finger, water when it is dry, then empty the saucer. In cool weather, water much less often. Indoors, keep the mix on the dry side. Fertilizer is unnecessary: lean soil concentrates the flavor of the leaves, and feeding at planting time is enough.

Potting mix

It needs warm, light, airy soil with excellent drainage, sandy or loamy, with a pH near neutral (6.5 to 7.5) or even slightly acidic. It will not tolerate heavy soil that stays wet, especially in winter. In that case, grow it in a raised bed or a container. The pot should be at least 8 in wide and deep, with plenty of drainage holes; fill it with a peat-free, soil-based mix blended with about one quarter horticultural grit.

Temperature

Tarragon likes warmth without extremes. Indoors, like most herbs, it is happy at 64–70 °F during the day and 55–61 °F at night.

Outdoors it is a hardy plant that dies back in winter and regrows from the base in spring; it is grown in USDA zones 3a to 8b. Cold alone is rarely what kills it; the combination of cold and wet is. Russian tarragon overwinters outside without trouble unless the ground is waterlogged. French tarragon, more delicate, is best grown in a pot that spends the winter in a cold greenhouse, on a porch or at the foot of a wall, out of the rain. In the ground, leave the dry stems standing over winter, mulch heavily or cover the crown with a cloche.

Repotting

Plant or repot in spring, after the last frost, spacing French tarragon 8 in apart and Russian tarragon at least 12 in apart. In a pot, repot when roots grow out of the drainage hole, ideally in early spring. Acclimate an indoor-raised plant gradually to the outdoors, starting in part shade.

Tarragon is a short-lived perennial: divide clumps every two to four years to keep plants vigorous and flavorful.

Pruning

In spring, as new growth appears, cut last year’s stems back to the young shoots at the base. Through the season, harvest the stem tips regularly to keep tender leaves coming. Pinch out stems carrying flower buds to prolong the harvest, and a trim in mid to late summer rejuvenates the plant.

Tarragon is best used fresh, since it loses its aroma quickly when dried. To keep some, dry it in a dark, airy place, or freeze the chopped leaves.

Propagation

French tarragon can only be propagated vegetatively:

• Division: in spring, just as new shoots emerge. The roots are brittle, so cut the clump with a knife rather than a spade. Each clump yields three to five plants.
• Cuttings: early in the morning, take young stems 4–6 in long, cut just below a node, strip the lower third of the leaves, dip the base in rooting hormone and insert it in warm, moist mix, misting regularly. Take softwood cuttings in summer or semi-ripe cuttings in late summer.

Russian tarragon is sown in spring on the surface, barely covered, in a warm, bright spot, or directly outdoors from mid-spring.

Common problems

• Plant disappears over winter: waterlogged soil, or French tarragon left outside in the rain.
• Yellowing leaves, rotting crown: root or crown rot from overwatering or poor drainage.
• White powdery coating on leaves: powdery mildew.
• Orange or brown pustules: rust.
• Plant declining: a soil fungus, honey fungus, occasionally attacks it.
• Bland flavor: Russian or seed-grown tarragon, too little sun, or soil that is too rich.
• Tiny flies around the pot: fungus gnats, encouraged by mix that stays too wet.

One symptom can have several causes: look at soil moisture, light and the condition of the roots together.

Toxicity

Tarragon is toxic to dogs, cats and horses: its essential oils cause mild vomiting and diarrhea. Avoid growing it where pets can reach it. For people, occasional use in culinary amounts is considered safe. The essential oils, especially in the roots, can cause contact dermatitis in sensitive people.