Eggplant / Aubergine (Solanum melongena) growing guide

Quick facts

Category: fruiting
Difficulty: advanced
Days to harvest: 80 to 110 days
Harvest type: continuous production over weeks or months
Spacing: 50 cm between plants

Environment

Temperature: 20–30°C
pH: 5.5 to 6.5
EC (hydroponic): 2 to 3 mS/cm
Daily light: 22 to 30 mol/m²/day (strict, will fail outside this range)

Climate and zones

USDA zones: 10 to 13 (winter low around -1°C or warmer)
Frost tolerance: frost sensitive (dies at first frost)
Season: warm (summer crops, frost-sensitive)

Viable growing environments:

outdoor year-round (in zone)
outdoor in growing season (annual)
unheated greenhouse / hoop house
heated greenhouse
indoor (heated home)
indoor hydroponics under grow lights

USDA zone bounds reflect outdoor year-round survival. Anywhere outside the bounded zone range, this crop still grows as an annual in the warm months (outdoor_seasonal), under cover (greenhouse), or indoors under lights.

Growing systems

Eggplant works in:

drip / Dutch buckets
media bed (ebb and flow)
soil bed

Root mass is heavy - thin-channel systems (NFT, vertical towers) can't hold this crop mechanically, hence the system list above.

Growing media

The substrate the roots sit in. Choice depends on the system (clay pebbles don't fit NFT channels; rockwool isn't used in media beds) and the crop (eggplant works in the media listed below).

Medium	pH effect	Water retention	Bacterial surface
Expanded clay pebbles (LECA)	neutral / inert	low	high
Coco coir (Coconut coir)	slightly acidic	high	moderate
Perlite (Expanded volcanic glass)	neutral / inert	very low	low
Rockwool (Mineral wool)	alkaline until pre-soaked	very high	low
Soil-based mix (Potting soil)	varies by source	high	high

Bacterial surface area matters for aquaponics: clay pebbles, lava rock, and pumice double as biofilter substrate. Low-surface media (rockwool, perlite, pea gravel) work in hydroponics but need a separate biofilter in aquaponics.

Nutrient demand by stage

NPK ratios are relative weights at each growth stage; the nutrient mix calculator scales them to absolute grams or ml. EC targets shift through the plant's life: seedlings need a much lighter solution than fruiting adults.

Stage	N	P	K	EC target (mS/cm)
seedling	1	1	1	1
vegetative	3	1	2	2.2
flowering	2	2	3	2.5
fruiting	1	2	4	2.8

Companion-growing notes

Heavy uptake of potassium, calcium. Co-grown crops with the same demand will end up deficient even at "correct" EC. Plan around this in shared reservoirs.
High transpiration. Reservoir level will need regular top-ups during fruiting or flowering.

Aquaponics suitability

Not recommended for pure aquaponics. Fish waste alone doesn't provide enough of the nutrients this crop demands (typically potassium, calcium, or boron). It can be grown in a hybrid system where the reservoir is supplemented with hydroponic-style nutrients, but expect to dose actively.

Care notes

A productive hydroponic crop similar in requirements to peppers and tomatoes. Dutch bucket, drip, or large DWC systems with staking. EC 2.0-3.5 mS/cm. pH 5.5-6.5. Temperature: 22–30°C (heat-loving; growth stalls below 18°C and frost kills the plant). Very high light (DLI 20-30 mol/m2/day). From transplant to first harvest: 65-80 days. The plants are medium to large (60–120 cm depending on variety) and benefit from staking or caging, especially when carrying multiple heavy fruits. Japanese and Chinese types are easier to manage in hydroponic systems than large Western types because the slender fruits are lighter and the plants are often more compact. Pollination: eggplant flowers are self-fertile but benefit from vibration to release pollen. Shake the plant gently or use an electric toothbrush on flower clusters. Harvest when the skin is glossy and the flesh gives slightly to pressure. Overripe eggplant has dull skin, brown seeds, and bitter flavor. Each plant produces 5-15 fruits over a season depending on variety. Flea beetles are the most common pest (they riddle the leaves with tiny holes); row cover or spinosad spray controls them.

Notable varieties

A starting shortlist of cultivars worth knowing about. Not exhaustive: the seed catalogs list hundreds of named varieties. These are the ones home growers commonly choose between.

Cultivar	Type	Days	Size	Notes
Black Beauty	heirloom	80	600 g	Pre-1902 heirloom Italian-type. Large dark purple teardrop fruit, the supermarket default. Productive on bushy plants. Needs warm soil to set fruit; struggles in cool summers.
Ichiban	hybrid	65	110 g	F1 Japanese-type. Long thin 20-25cm fruit, mild flesh with very few seeds. Earlier than Italian eggplants by 2 weeks; useful in zone 5-6 where the long season hurts Italian types. Continuous harvest from one plant for 8+ weeks.
Rosa Bianca	heirloom	90	400 g	Italian heirloom with rose-purple skin streaked white. Mild creamy flesh, less bitter than dark eggplants, almost no salting needed. Longer season than Black Beauty; best in zones 7+. Beautiful enough to grow as ornamental.
Listada de Gandía	heirloom	80	300 g	Spanish heirloom, purple and white striped 15-20cm fruit. Thin skin, mild flesh. Productive in hot dry climates; less reliable in cool maritime conditions.
Thai Long Green	open-pollinated	80	100 g	Pale green thin 25-30cm fruit for Thai curry and stir-fry. Tender flesh that needs no salting. Heat-tolerant; thrives in zone 9+ where Italian types stall.