Roma tomato / Plum tomato (Solanum lycopersicum) growing guide

Quick facts

Category: fruiting
Difficulty: intermediate
Days to harvest: 75 to 95 days
Harvest type: continuous production over weeks or months
Spacing: 60 cm between plants

Environment

Temperature: 18–28°C
pH: 5.5 to 6.5
EC (hydroponic): 2 to 3.5 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

Roma tomato works in:

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

Root mass is very 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 (roma tomato 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	2.6
fruiting	1	2	4	3

Companion-growing notes

Heavy uptake of potassium, calcium, phosphorus. Co-grown crops with the same demand will end up deficient even at "correct" EC. Plan around this in shared reservoirs.
Releases compounds through the roots that can mildly inhibit other crops in the same reservoir or bed. The effect is usually subtle but worth knowing if neighbors look stunted.
Very high transpiration. Reservoir level drops fast once the plant is mature; expect daily top-ups and watch for EC creeping up as water evaporates faster than salts.

Aquaponics suitability

Compatible with typical aquaponics nutrient profiles. Fish waste provides enough nitrogen for healthy growth; supplemental potassium, calcium, and iron may still be needed depending on fish stocking density.

Care notes

A productive hydroponic tomato for sauce-making. Dutch bucket, drip, or large DWC systems. EC 2.5-3.5 mS/cm. pH 5.5-6.5. Temperature: 20–28°C daytime, 15–18°C night. High light (DLI 20-30 mol/m2/day). Determinate varieties (most Romas) grow as compact bushes (60–90 cm) that don't need the elaborate string training of indeterminate types. Stake or cage for support. From transplant to first harvest: 70-80 days. The concentrated fruit set produces a flush of 20-40 tomatoes over a 3-4 week period, ideal for batch sauce-making. For fresh pasta sauce: halve the tomatoes, roast at 200°C until concentrated and slightly charred, then blend or pass through a food mill. For canning: blanch, peel, core, and process in a water bath or pressure canner. San Marzano varieties are the standard for Neapolitan pizza sauce (crushed San Marzano tomatoes, salt, basil, and olive oil, uncooked on the pizza). Blossom end rot is the main quality issue; maintain consistent calcium and watering.

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
San Marzano	heirloom	80	110 g	Italian DOP heirloom from volcanic soil near Vesuvius. Indeterminate vines, elongated thin-skinned fruit with low water content and dense flesh. The canonical pizza-sauce tomato. Needs staking and benefits from drier conditions; foliar disease prone in humid climates.
Roma VF	open-pollinated	75	80 g	The supermarket plum tomato. Determinate, sets all its fruit in a 3-4 week window. VF = resistance to Verticillium and Fusarium wilt. Reliable producer, average flavor, ships well.
Amish Paste	heirloom	85	230 g	Pennsylvania Amish heirloom. Indeterminate, larger than most paste tomatoes (often 220-280g). Less acidic than San Marzano, makes thicker sauce with less reduction. Slower to ripen.
Opalka	heirloom	85	200 g	Polish heirloom. Elongated horn-shaped fruit up to 15cm. Thin walls, almost seedless, very dense flesh. Indeterminate. Excellent for sauce and drying; thin skin makes fresh use less practical.