A Seasonal Grow Calendar for Indoor Hydroponics — What to Plant and When

A standard outdoor grow calendar revolves around frost dates, day length, and rainfall. Indoor hydroponics removes all three of those constraints. But "you can grow anything anytime" doesn't mean "you should grow everything always" — there's still a calendar, just driven by different variables.

Here's how we think about scheduling a year of indoor hydroponic growing.

The four variables that still seasonalize indoor growing

1. Room temperature. Even climate-controlled rooms drift. A garage tent runs 8 °C cooler in January than July. Reservoir temperature follows, and so does dissolved oxygen. See why reservoir temp matters.
2. Daylight bleed. A south-facing window adds 4–8 hours of indirect light in summer and almost zero in winter. If your tent leaks light, your photoperiod is not what your timer says.
3. Electricity cost. Lighting and pumps run 16+ hours daily. Winter peak rates push the bill 30–50% higher in many regions. The lamp efficacy you bought matters more in February than August.
4. What you actually want to eat. Salad greens shine in summer dinners. Heavy fruiting crops match autumn comfort food. Cool-season crops (kale, chard) feel right in winter even when they're grown indoors year-round.

The year, month by month

January — Reset month

• Why now: lowest sunlight, coldest room, highest electricity rates. Don't start a new ambitious tomato grow this month.
• Plant: lettuce, bok choy, spinach, arugula. All forgiving, all low DLI.
• System focus: Kratky wins this month — no pump heat helps a cold room, no power draw helps the bill.
• Maintenance: deep-clean reservoirs, replace airstones, calibrate meters. Recharge the system for spring.

February — First long succession

• Start a 10-day succession of lettuce and herbs. Plant 4 new seedlings every 10 days.
• Begin tomato seedlings indoors if you plan a March transplant to DWC.
• Pre-mix nutrient stock solutions while the rest of the kitchen is quiet.

March — Spring ramp

• Move tomato and pepper seedlings into Dutch buckets or DWC. They'll start producing by June.
• Basil, cilantro, and parsley seedlings into separate herb stations.
• First strawberry transplants if you have a vertical tower.

April — Daylight tipping point

• South-facing rooms hit useful indirect light again. Lower lamp PPFD by 10–15% to save power; the window contributes.
• Start cucumber and bell pepper seedlings.
• Resume aggressive succession on leafy greens — daily salad harvest by month-end.

May — Tomato peak preparation

• Tomato plants in flowering stage. Bump DLI to 25+, run 14h photoperiod.
• Mint, cilantro, parsley in continuous succession.
• Check room temperature daily — May warm spells push reservoirs above 24 °C. See oxygen deficit.

June — Heat management month

• Indoor rooms peak at 28–32 °C. Move pumps to night cycles; insulate reservoirs.
• Switch leafy greens to heat-tolerant cultivars (oak-leaf lettuce, lemon basil, Thai basil).
• First tomato harvest. First pepper harvest if peppers transplanted in March.

July — Summer abundance

• Cherry tomato, basil, cucumber all at peak.
• Strawberry second flush.
• Consider pausing leafy greens — outdoor markets are full of cheap lettuce; your electricity is better spent on fruiting crops.

August — Heat ceiling

• Reservoir cooling is the limiting factor. Add chillers or pause heat-sensitive crops.
• Start fall lettuce succession indoors — cooler rooms by October will welcome them.
• Begin overwintering perennial herbs (mint, oregano) by cutting back to root mass.

September — Transition

• Outdoor heat drops; indoor reservoirs stabilize.
• Final tomato harvest from spring plantings. Pull dying plants, sanitize systems.
• Start kale, chard, and bok choy for fall crops.

October — Cool-season pivot

• Kale, swiss-chard, spinach, arugula. All thrive at 16–20 °C.
• Outdoor sunlight drops below useful threshold. Bump lamp PPFD back to spec.
• Last call to repair or replace equipment before winter.

November — Winter prep

• Lettuce succession in full swing. Eight cycles per square foot per year hits its peak rhythm now.
• Insulate reservoirs, replace airstones, audit fan filters before holiday season.
• Reduce non-essential systems (vertical towers, complex aeroponics) if electricity cost is biting.

December — Holiday harvest

• Fresh salad greens through the holidays.
• Microgreens for garnish (radish, pea, sunflower) — 10-day cycles fit perfectly.
• Skip ambitious new builds until January reset.

Succession planting math

For continuous lettuce harvest:

• Cycle length: 35–45 days seed-to-harvest.
• Plant 4 new seedlings every 10 days.
• After week 10: 1 head harvested per week, indefinitely.
• Annual yield from a single 2×2 ft tent: ~40–50 heads.

For basil:

• Cycle length: 50–60 days to first significant harvest, then cut-and-come-again for 4–5 months.
• Plant 2 new seedlings every 4 weeks.
• Continuous harvest, no gap.

For tomatoes:

• Cycle length: 120–180 days seed-to-fruit.
• Plant 1 seedling every 8 weeks; you'll always have one cycle bearing fruit.
• Annual yield: 3–4 plants × 2–4 kg = 8–16 kg of tomato per year per Dutch bucket.

Crops that surprise people year-round

• Strawberry: day-neutral cultivars (Albion, Seascape) flower regardless of photoperiod. Year-round production in aeroponic towers.
• Microgreens: 7–14 day cycles independent of season. Highest revenue per square foot for commercial growers.
• Mint: essentially indestructible. Plant once, harvest forever.
• Hot peppers: perennial in hydroponics. A mature pepper plant produces for 3+ years if you don't kill it with overwatering.

The honest take

You can grow anything in any month indoors. What changes is how hard the system has to work — and how much that costs you in electricity, attention, and replacement parts. A year-round indoor garden run on autopilot favors leafy greens, herbs, and microgreens. Fruiting crops repay attention with summer abundance. Use winter for system maintenance and the easy crops; use summer for the ambitious ones.

For where to start if you're building your first system, see hydroponics for beginners. For sizing the lighting that drives any of this, see watts per plant.