Fennel vs Dill for Hydroponic Growing (2026)
Dill produces 10–20 g of harvestable fronds in 28–42 days, while fennel fronds are available in 30 days but fennel is allelopathic - it suppresses growth of nearby plants - making dill the safer companion crop and fennel best grown in isolation.
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Fennel and dill are both anise-flavoured herbs with similar cycle times (28–42 days for dill, 30 days for fennel fronds). The critical distinguishing fact: fennel is allelopathic, releasing chemicals through its roots that suppress growth in most neighbouring plants. This makes fennel a system-isolation requirement - it cannot share a reservoir or channel with any other crop. Dill has no such property and is a safe companion herb.
Side-by-Side Comparison
| Feature | Fennel | Dill | |---------|--------|------| | Difficulty | Moderate | Moderate | | Days to First Harvest | 30–120 | 28–42 | | pH Range | 6.0–7.0 | 5.5–6.5 | | EC Range (mS/cm) | 1.0–1.8 | 1.0–1.6 | | Light (h/day) | 12–14 | 12–14 | | Water Temp (°C) | 16–22 | 16–22 | | Yield per Plant | 15–25 g fronds | 10–20 g/plant | | Key Flavour Profile | Anise, sweet | Fresh dill, anise-like |
Where Fennel Wins
- Dual-harvest: fronds ready at 30 days, full bulb at 90–120 days - two product types from one plant.
- Slightly higher frond yield (15–25 g vs dill's 10–20 g per harvest).
- Unique bulb format has very high market value; no substitute exists for fresh fennel bulb.
Where Dill Wins
- No allelopathic compounds - safely integrates into mixed herb systems.
- More consistent harvest window (28–42 days vs fennel's wide 30–120 day range).
- Slightly lower EC ceiling (1.6 vs fennel's 1.8) suits lower-nutrient systems.
Growing Them Together
Not recommended. Fennel's allelopathic root exudates suppress dill and most other herb growth. If you grow both, they must be in completely separate systems - not just separate channels in the same reservoir. Different rooms or at minimum different enclosed reservoirs with no shared drainage.
Which Should You Grow?
- Choose Dill if you grow in a mixed herb system and cannot dedicate an isolated setup to a single crop.
- Choose Fennel if you have a dedicated single-crop system and want both frond and bulb production from the same planting.
- Grow both if you have two completely separate systems - dill in your main herb system, fennel isolated in its own dedicated unit.