cool season · Tropaeolaceae
Growing Nasturtium in Utah
Edible flowers and leaves — peppery like watercress. Trap crop for aphids — keeps them off vegetables.
Schedule (May 15 last frost)
When to do what
Direct sow
5/15
First harvest
7/3
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
Direct sow
Seed depth
0.5″
Plant spacing
10″
Row spacing
12″
Germination temp
55–75°F
Days to maturity
50 days
How we grow it
Step-by-step
- 1.
Direct sow 0.5″ deep, 10″ apart
Soil should be at least 55°F before sowing — black plastic mulch laid down two weeks ahead helps in our cool springs. Water in deeply.
- 2.
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.
- 3.
Harvest around day 50
Days-to-maturity is a rough guide — taste, color, and size are the real signals. Edible flowers and leaves — peppery like watercress. Trap crop for aphids — keeps them off vegetables.
From the farm
What we’ve learned growing nasturtium
Nasturtium earns its space in the garden because pollinators don't care about your tomato yield unless something invites them in. Plus, nasturtium pairs surprisingly well with vegetable beds — interplanted strategically, it acts as a trap crop, a pollinator beacon, or just a reason to walk the rows in July when the work is most relentless.
Pests & problems
Tropaeolaceae family pressures in Utah
Nasturtium shares its troubles with nasturtium. 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 — actually a feature: nasturtiums are an excellent trap crop, drawing aphids away from vegetables. Cut and compost the heavily-infested plants.
Disease 1
Generally disease-free in Utah's dry climate.
Companion planting
What to plant near (and away from) nasturtium
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
- ✓Almost everything — broadcast as a trap crop and pollinator magnet.
Plant away from
Bad companions
- ✗Nothing significant.
Crop rotation
Self-sows readily; treat as an annual that may volunteer the next year.
Harvest & storage
Picking, keeping, preserving
Cut flowers
Cut in early morning when stems are turgid. Strip lower leaves, plunge into clean water immediately. Recut stems at a 45° angle once inside, ideally underwater. Change vase water every 2-3 days for longest vase life.
Drying
Hang small bundles upside down in a dark, dry, ventilated space. 2-3 weeks. Best for everlasting flowers (statice, strawflower) and seed heads. Most fresh-cut flowers don't dry well — they crumple instead of preserving form.
Mistakes we’ve made
Common ways to fail at nasturtium
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:Nasturtium seeds want exactly 0.5" of cover — about half an inch — about a fingernail deep. 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.
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 nasturtium
+Can I direct-seed nasturtium in Utah?
Yes. Direct sow, wait until soil temperature hits 55°F (use a soil probe thermometer; air temp is misleading). Sow 0.5" deep, 10" apart. Black plastic mulch laid 2 weeks ahead of sowing warms the soil 8-10°F faster.
+Why are my nasturtium 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 nasturtium survive a late frost in Utah?
Nasturtium 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 nasturtium take from seed to harvest?
50 days from direct sowing. 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 nasturtium plants?
10" between plants in the row, 12" 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).
Sources:Johnny’s Selected Seeds·USU Extension·Cross-checked with our greenhouse logs.