cool season · Asteraceae
Growing Tarragon in Utah
French tarragon doesn't come true from seed — propagate from cuttings or buy plants. Russian tarragon from seed has weaker flavor.
Schedule (May 15 last frost)
When to do what
Start indoors
—
Transplant out
5/1
First harvest
7/31
Dates are calibrated for SUS Farms (Sevier County, Zone 6a, last frost May 15). For your own date, use the interactive calendar.
Planting
How deep, how far apart
Method
Start indoors
Seed depth
0.0625″
Plant spacing
18″
Row spacing
24″
Germination temp
60–75°F
Days to maturity
90 days
How we grow it
Step-by-step
- 1.
Start indoors 0 weeks before last frost
Seed-starting mix in 2" or 4" cells. Bottom heat at 60–75°F until germination, then drop to room temperature. Light from a clip lamp 14–16 hours a day, 2" from the leaves.
- 2.
Harden off for 7 days before going outside
Day 1: 1 hour outside in shade. Add an hour and more sun each day. Skip the day if it’s windy or below 50°F. After day 7 the plants stay outside.
- 3.
Transplant 18″ apart in rows 24″ apart
Soil should be at least 60°F before transplanting — black plastic mulch laid down two weeks ahead helps in our cool springs. Water in deeply.
- 4.
Mulch and water consistently
2" of straw or wood chip mulch around the base. Drip line at the surface. Aim for 1" per week — including rain — measured at soil level, not by the calendar.
- 5.
Harvest around day 90
Days-to-maturity is a rough guide — taste, color, and size are the real signals. French tarragon doesn't come true from seed — propagate from cuttings or buy plants. Russian tarragon from seed has weaker flavor.
From the farm
What we’ve learned growing tarragon
Herbs like tarragon pull double duty on the farm — they flavor what we cook, attract beneficial insects to the vegetable rows, and most are forgiving enough to survive an inattentive week. We grow most of our culinary herbs in raised beds near the kitchen entrance; the ornamental and pollinator-magnet varieties go out in mixed border plantings.
Pests & problems
Asteraceae family pressures in Utah
Tarragon shares its troubles with lettuce, sunflower, zinnia, marigold, calendula, cosmos, dahlia. The pests and diseases below show up most years; the fixes are what we actually do, not what catalogs sell.
Scout weekly during the growing season — most outbreaks are 10x easier to manage when you catch them in week one.
Pest 1
Aphids — colonies on undersides of new growth. Beneficial insects (lacewings, ladybugs) handle most outbreaks if you stop spraying broad-spectrum insecticides.
Pest 2
Slugs (lettuce especially) — rasped holes in leaves overnight. Diatomaceous earth, beer traps, or copper tape around bed edges.
Pest 3
Earwigs — pinch holes in flower petals at night. Roll up newspaper, leave overnight, dump in soapy water in the morning.
Disease 1
Powdery mildew — late-summer issue. Most common on zinnias; pick resistant cultivars (Profusion series).
Disease 2
Lettuce drop (Sclerotinia) — sudden wilting at the base. Improve drainage, mulch shallowly, rotate every 3 years.
Companion planting
What to plant near (and away from) tarragon
Most companion-planting charts you see online are folklore. The pairings below have either USU Extension research, Cornell vegetable MD pages, or our own multi-year farm logs behind them.
Plant near
Good companions
- ✓Tall flowers (zinnias, sunflowers) shade lettuce in summer to delay bolting
- ✓Carrots (no competition)
- ✓Onions (pest deterrent)
Plant away from
Bad companions
- ✗Beans (lettuce can stunt bean germination)
- ✗Dense plantings without airflow (mildew)
Crop rotation
Less critical than for Solanaceae or Brassicas — Asteraceae are mostly pest-light. Still good practice to move 2-3 years.
Harvest & storage
Picking, keeping, preserving
When to pick
Mid-morning, after dew dries but before the heat rises. Essential oil concentrations peak just before flowering — pinch flower buds for the strongest flavor. Pick the upper third of the stem, never strip a plant of more than 30% of its leaves at once.
Drying for storage
Hang small bundles upside down in a dry, dark, ventilated room — attic, garage, or closet works. 10-14 days for most herbs. Store dried leaves in airtight glass jars away from light. Quality holds 1 year. Beyond that, the herbs are still safe but flavor fades fast.
Freezing
Better than drying for high-water herbs (basil, parsley, cilantro). Chop, pack in ice cube trays with a splash of olive oil, freeze, transfer cubes to a labeled bag. Drop straight into hot dishes — no thaw needed.
Mistakes we’ve made
Common ways to fail at tarragon
Each of these has cost us a season at some point. Easier to learn from someone else’s lost crop than your own.
Planting too deep
The fix:Tarragon seeds want exactly 0.0625" of cover — about barely covered with a sprinkle of fine soil. Deeper than that and the seedling exhausts itself before reaching light. Carrots and lettuce especially: shallow is right; sprinkle, then cover with a dusting of soil and tamp gently.
Skipping the harden-off step
The fix:Plants raised under indoor lights have soft cuticles and weak stems. Move them straight outside and they sunburn, snap in wind, or wilt and never recover. The 7-day gradual sun exposure is mandatory, not optional.
Watering on a calendar instead of by need
The fix:Stick a finger or screwdriver 4" into the bed. Damp at depth = wait. Dry at depth = water deeply. Calendar watering ignores rain, heat waves, and seasonal evapotranspiration — leading to either drought stress or root rot.
Ignoring soil pH
The fix:Most Utah backyard soil tests at pH 7.4-8.4 (alkaline). Iron and zinc become unavailable to roots above pH 7.5 — leaves yellow, growth stalls. A $20 mailer test from USU Extension tells you exactly what your soil needs. Sulfur amendment in fall, foliar iron mid-season as needed.
Letting heat-bolt happen mid-season
The fix:Cool-season crops bolt (go to seed, become bitter) when night temps stay above 70°F. Plant for an early-spring AND late-summer harvest, with a heat gap in between. Fall plantings of lettuce, spinach, and brassicas are often better than spring ones in Utah.
Common questions
Frequently asked about tarragon
+When should I start tarragon indoors in Utah?
In Sevier County (last frost May 15), start 0 weeks before — that's roughly May. If you're at higher elevation (Park City, Logan), add 2 weeks. Lower elevation (Salt Lake, St. George), subtract 2-4 weeks. Use the interactive seed-starting calendar at /seeds/calendar to dial it in for your specific frost date.
+Why are my tarragon leaves turning yellow?
Three usual suspects. (1) Iron chlorosis — yellow leaves with green veins is the Utah classic; the cause is alkaline soil locking up iron. Foliar iron rescues the season; sulfur amendment in fall fixes it long-term. (2) Nitrogen deficiency — entire leaf yellow including veins, starts with old leaves. Side-dress with compost or a slow-release organic fertilizer. (3) Overwatering — yellowing accompanied by soft, mushy stems means the roots are drowning. Check drainage; reduce water frequency.
+Will tarragon survive a late frost in Utah?
Tarragon is a cool-season crop and tolerates light frost (down to ~28°F) once established. Tender seedlings just out of the greenhouse are more vulnerable — cover with floating row cover when overnight forecasts show below 35°F. After hardening off properly, mature plants of this family typically shrug off late-spring frosts that would kill warm-season crops.
+How long does tarragon take from seed to harvest?
90 days from transplant. Add 0 days for the indoor seed-starting phase, so total time from sowing seed to first harvest is roughly 90 days. Days-to-maturity is a baseline — cool springs add a week or two; hot summers can speed up by similar amounts. Use it for planning, not as a strict calendar.
+What's the spacing between tarragon plants?
18" between plants in the row, 24" between rows. That gives mature plants room to fill in without competing. Closer spacing reduces yield per plant; wider spacing wastes garden space. The numbers come from average mature plant size at full vegetative growth — adjust slightly for compact varieties (closer) or large heirlooms (wider).
Same family (Asteraceae)
Related crops
Sources:Johnny’s Selected Seeds·USU Extension·Cross-checked with our greenhouse logs.