Glossary

The giant growers’ vocabulary.

Seed coat, fruit set, OTT, DAP… The world of giant vegetables has its own jargon. Here, in plain words, is every term used across our growing tips and our seed pedigrees.

On the growing-tips pages these words appear underlined: hover them — or tap them on mobile — to read the definition without leaving the page.

Estimate my pumpkin’s weight (OTT method)

63 terms

Sowing & germination

Cotyledon

Embryonic leaves already formed inside the seed, thick and rounded. They feed the seedling until the true leaves appear, then yellow and drop. Wide, green, fully opened cotyledons usually signal a vigorous plant.

Damping-off

Caused by soil fungi (Pythium, Rhizoctonia, Fusarium) that thrive in a soaked substrate, still air and mild temperatures. The stem pinches at medium level and the plant topples. Prevention: clean substrate, measured watering, ventilation from the cotyledon stage on.

Drainage

Good drainage stops water sitting at the bottom of the pot and starving the roots of oxygen. You build it into the substrate itself (perlite, coarse sand, bark) and with enough drainage holes. "Moist but never soaked" is the whole aim.

Emergence

The visible arrival of the young shoot above the medium, 4 to 6 days after sowing under good conditions. Even emergence — every plant within 24–48 hours — signals well-controlled temperature and moisture.

Germination

The phase in which a rehydrated seed kept warm breaks dormancy: the radicle (first root) pierces the seed coat, then the shoot pushes towards the surface. For a giant pumpkin this needs 25–30 °C and 65–80 % humidity, and usually takes 4 to 6 days.

Greenhouse

By storing the day’s heat, a greenhouse lets you sow around 15 April and plant in early May — two to three weeks ahead of outdoors, and that many extra growing days over the season. In exchange it needs daily ventilation: above 30–35 °C, pollination and growth both suffer.

Grow box

A tent, cabinet or small dedicated room fitted with lighting, a thermo-hygrometer and ventilation. It holds the 25–30 °C and 65–80 % humidity needed for fast, even germination whatever the weather outside. Before transplanting, its temperature is lowered step by step to prepare the plants for outdoor life.

Grow light

LEDs or tubes designed to cover the spectrum photosynthesis needs. For a giant pumpkin sowing, aim for 16–18 h of light and 6–8 h of night. Syncing that cycle with the sun (say 5 a.m. → 11 p.m.) makes the move outdoors more natural. Without enough light the seedling stretches: a long, thin, fragile stem.

Growing medium

A prepared growing support (peat, coco coir, compost, perlite…) that holds moisture while still letting air through. For a giant pumpkin sowing you want a fine, low-salt, free-draining medium with a pH of 6.2 to 6.8. Garden soil is too heavy and carries disease, so it is avoided at this stage.

Hardening off

Over several days the plants go outside for a few hours, first in shade then in sun, for longer each time. Leaves thicken their cuticle and the stomata learn to regulate. Skip it and transplanting brings sunscorch or thermal shock, costing one to two weeks of growth.

Misting

The technique used on seedlings: instead of re-wetting the whole pot, you mist the surface of the medium as soon as it starts to dry. The roots stay in an airy substrate, which limits suffocation and damping-off.

Non-chlorinated water

Chlorine and chloramine in tap water are hard on the embryo and on the substrate’s micro-life. Standing the water for 24 hours in an open container, running it through a carbon filter, or using rainwater all remove it. It should also be tempered, above 20 °C.

Relative humidity

The amount of water vapour in the air compared with the maximum it could hold at that temperature. Too low and the medium surface dries out, gluing the seed coat to the cotyledons; too high and damping-off sets in. Read it on a hygrometer, ideally paired with a thermometer.

Seed coat

The seed’s protective shell. It sometimes stays stuck to the cotyledons at emergence: moisten it to soften it, then ease it off gently. Forcing a dry coat tears the cotyledons and dooms the plant.

Seed viability

The share of seeds in a batch that can germinate under good conditions. Cucurbit seeds hold their viability for several years when kept dry, cool (fridge) and away from light, but it declines fast once they see heat or damp.

Seedling

The stage right after emergence: the plant still has only its cotyledons and lives off the seed’s reserves. Very sensitive to overwatering, temperature swings and low light — this is where most plants are lost.

Soaking

The seed goes into non-chlorinated water above 20 °C for roughly 12 hours. The coat softens, the embryo rehydrates, and germination starts faster and more evenly. Past 24 hours the seed runs out of oxygen and can suffocate — that is the hard limit.

Substrate

Any material that hosts the roots: potting mix, homemade blend, rockwool, coco coir… A substrate is called "airy" when it holds enough air pockets for the roots to breathe — decisive during the first days of growth.

Thermal shock

Cold water, a draught, or moving outdoors too quickly can drop root temperature by several degrees in minutes. The plant closes its stomata and growth stalls for days. Hence tempered water and gradual hardening off.

Transplanting

A delicate operation, as cucurbit roots hate being disturbed: handle the whole root ball without breaking roots, ideally late in the day or in overcast weather. Under glass: plant in early May. Outdoors: between 15 and 20 May, once all frost risk has passed.

Growing & nutrition

Assimilates

The products of photosynthesis (sugars and derived compounds) that the plant moves from the leaves to its growing organs. On a giant, nearly all assimilates converge on a single fruit — hence the importance of not hindering their transport, which depends on available water and on potassium.

Blossom end

The point where the female flower was attached. It is the thinnest part of the skin, and so the usual place for splits to appear during very fast growth (blossom end split). Inspect it daily and keep the area dry and off direct contact with the soil.

Calcium (Ca)

Calcium builds cell walls: it gives tissues their strength and keeps young organs working. On a giant putting on kilos a day, a strong skin means fewer splits. It moves poorly inside the plant and follows the water flow, so irregular irrigation creates local deficiencies even when the soil holds plenty.

Drip irrigation

A network of pipes with calibrated emitters delivering water litre by litre, straight into the root zone. It allows frequent, split applications, stable moisture through heat waves, and the addition of a nutrient solution — all without wetting the foliage or the fruit.

EC (electrical conductivity)

EC is one of the most widely used parameters for measuring the salinity of the saturated extract (ECe) or of irrigation water (ECw), because its value is proportional to the amount of dissolved salts. The point of measuring it is to find out whether soluble salts are present in high enough amounts to affect seed germination, plant growth or irrigation efficiency: past a certain threshold they hinder water uptake by the roots.

Evapotranspiration

The sum of water evaporated from the soil and transpired by the leaves. It spikes in heat, dry wind or strong sun: the same plant can double its consumption from one day to the next. This is why you work from the plant’s real consumption rather than a fixed number of litres per day.

Fertilisation

Fertilisation is the process of supplying a growing medium, such as soil, with the elements a plant needs to develop and with what maintains or improves soil life. The product used can be a fertiliser, a soil amendment, or a mixed fertiliser-and-amendment product.

Fruit set

The phenological stage in which the pistil turns into a fruit. In practice, the fertilised female flower stops yellowing, its ovary swells, and the young fruit starts growing. A failed set — incomplete pollination, extreme temperatures, too young a plant — ends in the fruit aborting within days.

Female flower ovary: this is what swells into the fruit

Fruiting

The production of fruit, or the time of year when that production happens. On a giant pumpkin it follows fruit set and runs for 80 to 120 days; this is when the plant can put on several dozen kilos a week, and when every watering or feeding mistake shows up directly in the final weight.

Leaf area

The combined area of every leaf on the plant. The larger it is, the more sugars photosynthesis makes for the fruit — but also the more the plant transpires and drinks. Giant growers routinely talk in tens of square metres of leaf for a single fruit.

Magnesium (Mg)

Magnesium is the central atom of chlorophyll and takes part in many metabolic reactions. A deficiency shows on older leaves, which yellow between the veins while the veins stay green — a common signal when the feeding is thrown off by excess potassium.

Micronutrients

Iron, manganese, zinc, boron, copper, molybdenum… The plant only uses traces, but each drives specific reactions: without them photosynthesis and metabolism stall, however perfect the NPK feed. Their availability depends heavily on soil pH.

Nitrogen (N)

Nitrogen builds leaves and vines, so it is central during vegetative growth — but overdone it produces lots of foliage without improving the plant’s ability to carry a big fruit, and it softens the tissues. It is not cut out during fruiting either: a plant maintaining a large leaf canopy still needs it.

Nutrient solution

A mix of water and nutrients prepared in a tank then delivered to the plant, usually by drip. Two values are checked before every application: pH, which governs uptake, and EC, which shows the salt concentration. This is the method that makes finely split feeding possible.

Osmotic stress

Water stress, or osmotic stress, is the abiotic stress (linked to the physical conditions of the environment) undergone by a plant when the amount of water it transpires exceeds the amount it takes up. On a giant pumpkin, whose leaves evaporate enormously, it shows as midday wilting — and if it repeats, as kilos lost on the fruit.

pH

pH expresses the balance between H⁺ (acidic) and OH⁻ (basic) ions in a solution: more H⁺ and the pH falls, more OH⁻ and it rises. In the garden it governs nutrient availability — outside the right window the fertiliser is there but the plant can no longer take it up. For giant pumpkins, aim for 6.2 to 6.8.

Photosynthesis

Photosynthesis is the process by which plants make their own food using sunlight. More precisely, they use light, water (H₂O) and CO₂ to produce sugar and oxygen. On a giant pumpkin the entire leaf area works for a single fruit — which is why the leaves are protected just as carefully as the pumpkin itself.

Potassium (K)

Potassium drives sugar transport towards the fruit and the plant’s water regulation, so it becomes important from fruit set onwards. A warning though: "more potassium" does not mean "more growth" — an excess of one element disturbs the uptake of the others.

Root zone

On a giant pumpkin it spreads over several metres and thickens under the canopy. The aim of irrigation is to keep it active, moist and oxygenated: neither dried out nor saturated. Watering outside that zone achieves nothing, and saturating it drives out the air the roots need.

Salinity

Fertilisers are salts. Too concentrated around the roots, they reverse the exchange: the plant can no longer take up water, even in moist soil. That is the mechanism of osmotic stress. Salinity is measured by EC, and controlled by splitting inputs rather than dosing heavily in one go.

Soil amendment

Compost, manure, lime, biochar… an amendment works on the support itself: structure, water-holding capacity, pH, biological activity. That sets it apart from fertiliser, which supplies directly available nutrients. On a giant pumpkin the two go together — living, airy soil makes far better use of feeding.

Stem (peduncle)

Water and sugars travel through the stem to swell the fruit. You want it healthy, thick and firmly attached, and you never lift a pumpkin by it. As the fruit grows, tension builds between fruit and stem: it is the first thing to inspect daily, because a split there can disqualify the fruit at a weigh-off.

Vegetative growth

The first part of the season: the plant builds its root system and leaf area without yet carrying a fruit. This is the factory being built, and its size sets how much energy will be available for the giant later. Aim for fast growth, but above all steady growth.

Pumpkin plant in the vegetative phase, 40 days after germination

Genetics & pollination

Atlantic Giant

Bred in Canada by Howard Dill from the Mammoth, the Atlantic Giant is the genetic base of virtually every competition pumpkin grown today. All the major competition lines — and the weight pedigrees growers trade — descend from it.

Cucurbits

The botanical family of tendrilled plants with separate male and female flowers: pumpkins, squash, watermelons, melons, cucumbers, courgettes. Because the sexes are separate on the same plant, hand pollination is possible — and that is what makes giant genetics controllable.

Hand pollination

For squash, pumpkins and watermelons, you bag the male and female flowers the evening before they open, then in the morning (often 8–10 a.m., when pollen is most active) transfer pollen from the stamens onto the pistil and close the female flower again. That control locks in the fruit’s genetics — you know both mother and father — and improves the odds of a well-formed fruit.

Female flower protected by a net until pollination

Line

A line gathers the descendants of one cross, followed year after year. Among giant growers a line is read through its pedigree: the weights of the parent and grandparent fruit. That is what gives a competition seed its value — you buy a documented potential, not a promise.

Stabilized genetics

After several generations of selection and controlled self-pollination, the traits you want (vigour, shape, weight potential) pass on predictably. It is the opposite of an open-pollinated seed, whose father — and therefore behaviour — is unknown.

Competition & measuring

BES (Blossom End Split)

A split or tear at the blossom end, opposite the stem. It usually appears during very fast growth or after an irregular watering. The fruit is not eligible for competition.

A blossom end split starting on one of Nicolas’s pumpkins in 2025, 35 days after pollination

The same pumpkin a few hours later: the fruit is lost for competition

Official weigh-in

On the day, the fruit is inspected (integrity, stem, no split through to the cavity) then weighed on a certified scale in front of the judges. A fruit split through to the cavity is disqualified. Beyond weight, judges also look at overall quality, shape, colour, presentation and compliance with the rules.

OTT (Over The Top)

OTT is a measuring method that takes three measurements over the pumpkin with a tape or string: circumference (around the fruit, parallel to the ground), end-to-end (from the ground up over the fruit to the stem and back down at the blossom end) and side-to-side (perpendicular to the previous one, ground to ground). Together they give a volume, and therefore an estimated weight, via the OTT chart.

Shade cloth

A net or fabric that filters part of the radiation. On a competition fruit, skin left in full sun hardens, discolours and can scorch — defects judges spot instantly. Shading also limits heat build-up, and therefore evapotranspiration around the fruit.

SS (Stem Split)

A split or tear at the stem. The fruit is not eligible for competition if the split has reached the cavity. It is the classic result of excess tension between a fast-swelling fruit and a stem that cannot follow, or of a fruit turned too abruptly.

Giant-grower nomenclature

Clone (CL)

A fruit grown from a clone (rare, but it does exist in advanced growing). The plant is reproduced from a cutting rather than a seed, so it is genetically identical to the original — a way of running an outstanding genetic line again exactly.

DAP (Days After Pollination)

The number of days elapsed since pollination. It is used to track growth (e.g. 45 DAP) and compare fruit against one another. Mind the convention: DAP 0 is the moment of pollination itself, DAP 1 the day of pollination.

DMG (Damaged)

A damaged fruit (crack, hole, wound). Usually not eligible for competition. The tag appears next to a weight in results to flag that the fruit, though weighed, was not in a fit state to compete.

EST (Estimated Weight)

An estimated weight (usually via the OTT method), not officially weighed. Depending on the fruit’s shape and density, the gap with the real weight can reach 10–15 % — hence the tag, to avoid any confusion.

F / M (Female / Male)

F (Female) marks the female flower used in the cross, M (Male) the male flower. These tags let you read a pedigree precisely and know which way round the cross was made.

Female flower: in the centre, the five-lobed stigma where the pollen is placed

Genetic cross notation

A genetic cross is read in order: the first weight and name are the mother (e.g. 2169 Daho), the second the father (e.g. 1707.5 Bernard). The numbers are the parent fruit weights. This is a competition seed’s identity card — it tells you where the potential you are buying comes from.

OPEN (Open Pollination)

Uncontrolled pollination: bees, insects, wind… The father is unknown. The seed is still perfectly growable, but its pedigree is incomplete and its behaviour far less predictable than a controlled cross.

SELF (Self-pollinated)

Pollination within a single plant: the female flower was pollinated by a male flower on that same plant. It is the main tool for fixing a line, since the father’s and mother’s genetics are identical.

SIB (Sibling Pollination)

Pollination by a sibling plant: same genetics, same line, but a different plant. The cross stays controlled and documented, with slightly more genetic mixing than a SELF.

UOW (Unofficial Weight)

An unofficial weight, not validated at a weigh-off. Often used for fruit weighed at home or estimated. It appears in results for information only and does not count towards a ranking.

The weight calculator has its own page

Estimate your pumpkin’s weight from three tape measurements, using the OTT method.

Open the calculator →

The glossary makes most sense in practice.

See these terms in context in Nicolas’ growing guides.

Read the growing tips