Gadenin日本語Get the appWhat the plant is doing through the year
French tarragon is a herbaceous perennial that vanishes completely in winter. The top growth dies to nothing, the crown sits just under the surface, and thin creeping roots spread outward a few inches a season. There is no woody framework above ground to keep, which is why a pot that looks empty in late winter is usually not dead.
Growth starts late compared with chives or mint. New shoots push through as the soil warms past about 50F (10C), the plant runs up to eighteen to twenty-four inches (45 to 60 cm) of lax stems through summer, then the flavor thins and the lower leaves yellow as autumn comes. Everything you do for it is aimed at keeping that summer growth soft and leafy for as long as possible.
It is short-lived by perennial standards. A clump is at its best in years two and three, noticeably weaker in year four, and by year five it is usually a ring of thin shoots around a dead center. Planning to divide it is part of ordinary care, not a rescue operation.
Drainage first: the one thing it will not forgive
Tarragon comes from dry, open ground and its roots rot at the crown if they sit in cold wet soil. Summer wet is survivable. Winter wet, when the plant is dormant and taking up nothing, is what kills it. If you lose a plant over winter and dig up a mushy brown crown with clean roots on the outside, that is what happened.
In heavy soil, do not try to fix this with feeding or row cover. Fix it with height and grit. Plant on a raised area, a slope, or a mound four to six inches (10 to 15 cm) above the surrounding bed, and work coarse sand or fine gravel through the planting area until it drains visibly faster than the bed around it.
In containers the same rule applies with less margin. Use a free-draining mix rather than a moisture-retentive potting mix, raise the pot off the ground on feet through winter, and move it somewhere the rain does not fall directly into it once the top growth has died back.
| Situation | What you will see | What to do |
|---|---|---|
| Free-draining bed, full sun | Upright leafy stems, strong anise scent | Nothing beyond a summer trim and division every third year |
| Heavy clay, flat bed | Fine until autumn, then fails to reappear in spring | Lift and replant on a raised mound with grit, or grow it in a pot |
| Container in ordinary potting mix | Yellowing lower leaves, sour-smelling surface | Repot into a gritty mix, cut watering back sharply |
| Part shade | Long floppy stems, pale leaves, weak flavor | Move it; tarragon needs at least six hours of direct sun |
A useful test in autumn: water the planting spot heavily and come back in an hour. If there is still standing water on the surface, tarragon will not survive its second winter there.
Watering and feeding for flavor, not bulk
Water established plants deeply and infrequently. Let the top two inches (5 cm) of soil dry out before you water again, then soak the whole root area rather than sprinkling the surface. A plant kept constantly damp grows fast, tastes of very little, and goes into winter soft.
Feeding is where most people go wrong. Rich soil and regular nitrogen give tall, lush, pale growth with a flat flavor, and that soft growth is also the most likely to collapse in the first hard weather. One light feed as growth starts in spring is enough for the whole season in the ground. In a pot, a weak liquid feed once a month through the growing season is the ceiling.
The strongest-tasting tarragon most people ever grow is a plant on poor, gritty, sun-baked soil that gets watered less than its owner thinks it should. That is not neglect, it is the correct treatment.
Trimming, flowering and staying upright
The stems are lax and a mature clump flops outward from the middle by midsummer, especially after rain. Rather than staking, cut the whole plant back by about a third in early summer. It regrows bushier from lower down, and you get a large usable harvest from the trimmings.
French tarragon flowers rarely and poorly, and the small greenish buds that do appear never come to anything worth keeping. Pinch them off when you see them so the plant keeps putting its energy into leaf. If your plant flowers heavily and sets obvious seed, you almost certainly have the Russian kind rather than French.
Stop hard cutting about six weeks before your first expected frost. The plant needs a final stretch of undisturbed growth to build the crown that carries it through dormancy, and stems cut late do not have time to regrow.
What to write down
Keep three things on record and the plant becomes far easier to manage. First, the date shoots first broke the surface in spring, because tarragon emerges late and knowing your own normal date stops you digging up a live crown in the belief it has died. Second, the exact position of each crown, marked with a short cane before the top growth disappears in autumn, so you do not fork through it during winter tidying.
Third, the year each plant was divided or planted. Flavor decline is gradual enough that you will not notice it season to season, but a note saying a clump went in three springs ago tells you immediately that this is the year to divide it rather than wonder why the leaves taste thin.