Part 1: Chives (Allium schoenoprasum) — An Indoor Growing Profile
What chives are
Chives are a perennial Allium grown primarily for their hollow, aromatic leaves. They are exceptionally well-suited to indoor container growing because they:
- tolerate cooler temperatures,
- respond strongly to improved light (becoming denser and more upright),
- can be harvested continuously for long periods when kept in a vegetative state.
Why chives often become “leggy” indoors
The most common cause is simply insufficient light intensity (too low PPFD/DLI) and/or uneven light distribution (plants lean toward the brightest area). Secondary contributors include:
- warm temperatures paired with low light,
- high humidity with weak air movement (higher disease risk and softer growth),
- irregular watering (dry–soak cycles) that stress roots and can lead to tip burn.
Growth stages (container, indoor context)
- Germination — seed to emergence
- Seedling establishment — early root and leaf development
- Vegetative production (main operating state) — continuous leaf growth and harvest
- Flowering (generally avoided for leaf production) — diverts energy away from leaves
The ideal target for “continuous harvest” chives
- dense clumps with upright leaves,
- strong aroma and flavor (supported by cooler temperatures + adequate light),
- low fungal pressure (supported by appropriate VPD and airflow),
- predictable irrigation (best achieved with pot weight, or a calibrated moisture sensor).
Part 2: How to Grow Chives for Continuous Indoor Harvest (Soil + Pot)
1) Recommended environmental targets (setpoints)
Temperature
For compact growth and flavor quality:
- 16–20°C is an excellent operating range.
- Avoid spending long periods above 22–23°C unless light levels are high and airflow is strong.
Humidity and VPD (to reduce fungal issues)
A practical indoor target band:
- Relative humidity (RH): 45–60%
- VPD: 0.7–1.1 kPa during most of the day
Why VPD matters: fungal problems become more likely when conditions are cool + humid + stagnant, especially overnight. If RH spikes in the evening and temperature drops, VPD collapses. In that case, prioritize:
- gentle ventilation and/or dehumidification,
- a small temperature increase to prevent VPD from falling too low,
- steady air movement across the canopy (avoid blasting leaves directly).
2) Light strategy: intensity, duration, and lamp distance
Targets for compact, upright chives
- PPFD: 250–350 µmol/m²/s at the leaf tips (canopy)
- Photoperiod: 14–16 hours
- DLI: 12–18 mol/m²/day
Chives can survive at lower light, but they tend to become longer, thinner, and less dense.
Lamp distance and uniformity (practical method)
Your real goal is stable intensity at canopy height, with reasonably even coverage across your growing area.
If you can measure PPFD (PAR meter):
- Start with the lamp about 30–45 cm above the canopy.
- Measure center + four corners of the growing area.
- Adjust height/power until you consistently achieve 250–350 PPFD where the plants actually sit.
If you only have a lux sensor (e.g., BH1750):
Lux is not PPFD, but it works well as a control signal if you keep the sensor position consistent.
- A useful starting band at canopy height (for typical white LEDs) is often around 18,000–25,000 lux for 14–16 hours.
- Then refine based on plant response:
- Leggy/leaning growth: increase intensity (reduce distance or raise power), improve uniformity, rotate pots.
- Bleaching or crispy tips (with normal watering): slightly reduce intensity or increase distance, and check airflow/heat at canopy.
Uniformity tip: chives lean quickly under uneven light. If your coverage is not uniform, rotate pots every 2–3 days.
3) Soil and watering: “moist but airy” beats “constantly wet”
Chives like consistent moisture, but they do not like oxygen-starved roots.
The best control variable: pot weight
If you can implement it, pot weighing (load cell + HX711) is one of the highest-ROI measurements you can add.
A simple weight-based watering loop:
- Water until you reach a defined “wet weight” (or slight runoff).
- Let the pot dry down to a defined “dry threshold weight.”
- Avoid keeping the pot heavy/wet for multiple days.
If you use a soil moisture probe
Treat raw readings as relative until calibrated to your soil mix. Use the sensor mainly for trends and thresholds—pot weight remains the more reliable reference.
4) Nutrition: mild, consistent feeding for leaf production
Continuous harvest requires nutrients (especially nitrogen), but excessive feeding can produce soft growth and increase tip burn risk.
Practical approach:
- Begin light feeding after seedlings establish (typically after 2–3 true leaves).
- Maintain a mild, balanced feed rather than occasional strong doses.
- If you suspect salt buildup (tip burn, slowed growth, or high runoff EC): do a plain-water flush, then resume at a lower strength.
If you do not measure EC, it is generally safer to underfeed slightly and adjust based on growth and leaf color.
5) What you can measure, calculate, and proxy
Directly measurable (hobby-friendly)
- Air temperature and RH (e.g., SHT31/SHT35)
- Canopy lux (BH1750; relative control)
- Pot mass/weight (load cell + HX711)
- Optional: soil temperature
Derived (calculated)
- VPD (kPa) from air temperature + RH
- DLI from PPFD (or PPFD estimate) integrated over photoperiod
- Daily water use (evapotranspiration proxy) from the pot-weight curve
Not practical to measure continuously (use proxies)
- Root-zone nutrient strength → proxy with occasional runoff EC or symptoms (tip burn)
- True volumetric water content (VWC) → proxy with pot weight + calibrated moisture sensor
6) Recommended sensor stack (three tiers) and placement
Tier 1 (highest value per cost)
- Air T/RH: SHT31/SHT35 (I²C)
- Light (relative): BH1750 lux (I²C)
- Pot weight: load cell + HX711 (digital)
Placement
- T/RH: at canopy height, shaded from direct LED light, not in a strong airflow jet.
- Lux: at canopy height, consistent position and orientation.
- Load cell: a mechanically stable platform; avoid lateral forces on the pot.
Tier 2 (better irrigation and nutrition visibility)
- Capacitive soil moisture probe (analog)
- Handheld EC/pH for periodic spot checks
Tier 3 (precision and troubleshooting)
- PAR/PPFD meter for calibration and validation
- CO₂ sensor (SCD41) if you want to run higher light intensities efficiently
- Leaf wetness sensor for diagnosing mildew patterns
7) Calibration and validation (short plan)
- Load cell: calibrate with known masses (e.g., 2–10 kg). Do a quick weekly check with a reference weight.
- Soil moisture probe: two-point calibration for your soil:
- “Dry threshold” (dry enough that you would water soon, but not bone-dry)
- “Field capacity” (fully watered, drained for 30–60 minutes)
Validate by correlating against pot weight for several watering cycles.
- Lux → PPFD: best practice is to borrow/rent a PAR meter once and record paired lux + PPFD values at your typical lamp settings/heights.
8) Diagnostics: symptom + data pattern → likely cause → actions
Leggy, sparse, leaning leaves
- Pattern: low lux/PPFD or low DLI; often uneven coverage
- Actions: increase intensity, improve uniformity, rotate pots, keep temps in the recommended range
Brown tips (tip burn)
- Pattern: strong feeding and/or salt buildup; dry–soak watering cycles
- Actions: reduce feed strength, flush once with plain water, tighten watering control using pot weight thresholds
Fungal spots or mildew
- Pattern: high RH, VPD < 0.6 kPa for extended periods, weak airflow
- Actions: keep VPD mostly 0.7–1.1, increase gentle canopy airflow, avoid wet leaves, stabilize night RH
Soft growth and weak aroma
- Pattern: warm + low light, or excessive nitrogen
- Actions: lower temperature toward 16–20°C, raise light intensity, moderate nitrogen
Bleaching or washed-out patches
- Pattern: very high intensity and/or heat at canopy; high VPD (too dry) can amplify stress
- Actions: increase lamp distance slightly, improve airflow mixing, keep VPD in range
9) A simple year-round “operating recipe”
- 16–20°C, 45–60% RH, VPD 0.7–1.1 kPa
- 14–16 h light, 250–350 PPFD at canopy (or stable canopy lux that produces compact growth)
- Water by pot weight, not by calendar
- Harvest regularly but leave the base intact; avoid removing the entire plant at once