warm season · Solanaceae
Growing Big Boy Tomato in Utah
The classic 1-pound red slicer. Stake heavily. Use one slice per sandwich.
Schedule (May 15 last frost)
When to do what
Start indoors
3/27
Transplant out
5/22
First harvest
8/7
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
0.25″
Plant spacing
30″
Row spacing
36″
Germination temp
70–85°F
Days to maturity
78 days
How we grow it
Step-by-step
- 1.
Start indoors 7 weeks before last frost
Seed-starting mix in 2" or 4" cells. Bottom heat at 70–85°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 30″ apart in rows 36″ apart
Soil should be at least 70°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 78
Days-to-maturity is a rough guide — taste, color, and size are the real signals. The classic 1-pound red slicer. Stake heavily. Use one slice per sandwich.
From the farm
What we’ve learned growing big boy tomato
On our farm, big boy tomato is one of the rotations that grounds the season. We test new varieties every year alongside the staples — usually one experiment per row, surrounded by what we know works. Failures here are how we know what to recommend; the success stories make it into the catalog and onto our table.
Pests & problems
Solanaceae family pressures in Utah
Big Boy Tomato shares its troubles with tomatoes, peppers, eggplant, potatoes. 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
Tomato hornworm — large green caterpillars that strip leaves overnight in July. Hand-pick at dusk; Bt spray works on younger larvae.
Pest 2
Aphids on new growth — blast off with water before reaching for chemicals. Lacewings and ladybugs handle established colonies.
Pest 3
Iron chlorosis (yellow leaves with green veins) — Utah-specific from alkaline soil. Foliar iron rescues a season; sulfur amendment in fall fixes it long-term.
Disease 1
Early blight — concentric brown rings on lower leaves. Remove affected leaves, water at the base only, mulch heavily to block soil-splash spore transfer.
Disease 2
Verticillium wilt — wilting with no obvious bug or water stress. Soil-borne; rotate Solanaceae out of any bed showing this for 4+ years.
Companion planting
What to plant near (and away from) big boy tomato
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
- ✓Basil (improves flavor, repels thrips)
- ✓Marigold (root-knot nematode suppression)
- ✓Carrots (root depth difference, no competition)
- ✓Onions (allium pest deterrent)
Plant away from
Bad companions
- ✗Brassicas (heavy feeders that compete)
- ✗Fennel (allelopathic)
- ✗Walnut trees (juglone is toxic to all Solanaceae within 50 ft)
Crop rotation
Solanaceae bed in year 1 → Brassicas year 2 → Cucurbits year 3 → Legumes year 4 → back to Solanaceae year 5. The 4-year minimum prevents Verticillium and Fusarium from building up.
Harvest & storage
Picking, keeping, preserving
When to pick
Days-to-maturity (78 days from transplant) is a baseline. The real signals are color, size, and feel. The classic 1-pound red slicer. Stake heavily. Use one slice per sandwich.
How to harvest
Clean cuts with sharp pruners or scissors heal faster than ripped stems and reduce disease entry points. Harvest early morning when sugars are highest and the plant is fully turgid; afternoon-harvested produce wilts faster. Don't harvest when leaves are wet — fungal spores ride along.
Short-term storage
Most warm-season produce stores best at 50-55°F (NOT in the fridge — chilling injury reduces quality and flavor). Tomatoes especially: refrigeration kills flavor; counter-store at 55-65°F until ripe.
Long-term preservation
Freezing, canning, drying, and fermenting all preserve big boy tomato. Pick the method that matches your kitchen and how you actually use the harvest — frozen tomatoes are great for sauce but bad for sandwiches; dried herbs work everywhere; fermented vegetables shine in salads.
Mistakes we’ve made
Common ways to fail at big boy tomato
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:Big Boy Tomato seeds want exactly 0.25" of cover — about a quarter of an inch — about the diameter of a pencil. 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.
Planting too early
The fix:A warm-season crop set out before soil hits 60°F at 4" depth sits and sulks — sometimes for weeks before either dying outright or refusing to grow until July. Wait. Better to plant a week late than plant 3 weeks early into cold soil.
Common questions
Frequently asked about big boy tomato
+When should I start big boy tomato indoors in Utah?
In Sevier County (last frost May 15), start 7 weeks before — that's roughly March. 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 big boy tomato 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.
+Can I plant big boy tomato before the last frost date?
Not safely. Big Boy Tomato is a warm-season crop — even a light frost (28-32°F) kills the plant or stunts it for the rest of the season. Wait until soil hits 70°F at 4" depth AND there are no freezing temperatures in the 14-day forecast. In Sevier County that's typically the third week of May. Black plastic mulch + floating row cover let you push planting 7-10 days earlier.
+How long does big boy tomato take from seed to harvest?
78 days from transplant. Add 49 days for the indoor seed-starting phase, so total time from sowing seed to first harvest is roughly 127 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 big boy tomato plants?
30" between plants in the row, 36" 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.