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At H2L Robotics India, our teams annotate thousands of potato field images every day. Those images are captured by H2L Robotics BV's POTECTOR300 — an autonomous machine that moves through potato fields at 3 km/h, photographing plants and flagging diseased ones for manual removal. The annotation work that follows is precise and detail-oriented, but it is grounded in something fundamental: knowing what a potato plant is supposed to look like.

Understanding the potato plant's lifecycle — how it grows, what its leaves, stems, and flowers look like at different stages — is the foundation for recognising when something is wrong. A yellowing plant during senescence is healthy and expected. The same yellowing at peak vegetative growth is a red flag. This guide covers both, stage by stage.

The potato plant: a brief introduction

The cultivated potato, Solanum tuberosum, is a member of the Solanaceae family — the same botanical family as tomatoes, peppers, and aubergines. It originates from the Andean highlands of South America and has been cultivated for over 7,000 years. Today it is the world's fourth-largest food crop.

Unlike many crops, the potato is grown from a seed tuber — a small potato — rather than from seed. Each seed tuber has several eyes (buds) from which sprouts develop. The plant grows above ground as foliage and below ground as stolons (horizontal stems) from which tubers form. The edible portion we harvest is neither a root nor a fruit: it is a swollen underground stem.

H2L Robotics BV operates primarily in the Netherlands, working with two potato varieties: Spunta and Fontane. Both are susceptible to the viral diseases the POTECTOR300 is designed to detect — primarily PVY (Potato Virus Y) and PLRV (Potato Leafroll Virus).

Six growth stages: what the plant looks like

Plant scientists describe potato development using the BBCH scale — a standardised decimal code for phenological development stages. The potato lifecycle from planting to harvest covers BBCH stages 00 through 99, which can be grouped into six observable phases.

BBCH 00–09 Sprouting Days 1–40
The seed tuber lies underground in dormancy. Warmth and moisture trigger bud activity: the eyes of the tuber develop sprouts. No foliage is visible above the soil surface. The sprout is pale and etiolated — elongated in search of light. This entire stage happens out of sight. By the end of this phase, sprout tips are approaching or just breaking the soil surface.
BBCH 10–19 Emergence & leaf development Days 40–55
The first shoot breaks the soil surface. Compound leaves begin to unfurl along the elongating main stem — each leaf composed of several pairs of leaflets (typically 7–9 per leaf) arranged on a central rachis. At this stage the plant is fragile and light green. Each sympodial branch develops fewer leaves than the main stem. The foliage is sparse but growing fast.
BBCH 30–39 Stem elongation & canopy growth Days 55–75
The main stem elongates rapidly. The canopy can double in size every week during peak vegetative growth. Stolons extend horizontally underground from the base of the stem. Healthy plants at this stage have large, uniformly dark green leaves that spread outward, filling the row. Basal side shoots develop both below and above soil level. This is the stage most visible in aerial and ground-level field photography.
BBCH 40–69 Tuber initiation & flowering Days 60–90
Underground, stolon ends begin to swell — this is tuber initiation. Above ground, the plant reaches its maximum canopy height and density. Flower buds emerge at the top of the stem, followed by open flowers. Potato flowers are five-petaled, star-shaped, and visually similar to tomato flowers (reflecting their shared family). Colour varies by variety: Spunta produces white flowers; Fontane flowers are also predominantly white to pale lilac. Blossom signals the onset of tuber maturation underground. This is the densest, most lush point of the growing season.
BBCH 70–79 Tuber bulking Days 90–120
Flowers fade and drop. The plant's energy shifts decisively toward the growing tubers underground. Foliage remains largely green but starts to lose its peak vigour — the canopy may show the first subtle signs of leaf tip yellowing. Tubers are growing rapidly in size. This is when nutrient deficiencies or viral disease, if present, start to become more conspicuous against the otherwise still-green background.
BBCH 80–99 Maturation & senescence Days 120–150+
Foliage yellows progressively, starting from the lower leaves and moving upward. Leaves wither and die; stems collapse. The natural vine dieback signals that tubers are fully formed and developing thick skin. The plant is effectively dying in order to complete the tuber. At harvest, vines are typically fully brown and dry. The entire above-ground portion is removed mechanically before tubers are lifted from the soil.

Spunta and Fontane: two varieties, two canopy shapes

H2L's potato datasets cover two specific varieties, each with a distinct visual profile. Knowing which variety you are looking at helps set the baseline for what healthy looks like.

Spunta is a high-yielding Dutch variety developed in the 1960s. Its plants have a relatively open canopy structure with larger, more rounded leaflets. Healthy Spunta plants spread their leaves outward generously, creating a clearly visible row structure with visible gaps between plants. Uniform dark green is the healthy baseline.

Fontane is a more modern Dutch variety with a denser, bushier canopy. Its leaflets are slightly more pointed and the plant fills the row more compactly. Healthy Fontane rows appear tightly packed, with plants almost merging into continuous green strips. Any plant that breaks this uniformity — appearing paler, narrower, or with a different texture — is worth closer inspection.

Practical note: Both Spunta and Fontane are photographed during active vegetative growth and the tuber initiation/flowering stage — the POTECTOR300 operates before senescence. When annotating, the comparison is always against healthy neighbours in the same row, not against an abstract standard. A sick plant stands out from its context.

Why the lifecycle matters for disease detection

Viral disease symptoms in potato plants — particularly PVY and Leafroll — are not static. They appear, change, and intensify as the plant moves through its growth stages. Understanding this progression makes a significant difference to annotation accuracy.

  • During early vegetative growth, disease symptoms may be subtle — slight colour changes, very mild mosaic. These can be hard to distinguish from normal early-stage variation. The doubt label (sick-twijfel) exists for exactly these cases.
  • During peak vegetative growth and flowering, symptoms are most visible and contrast most clearly with healthy neighbours. This is the primary annotation window.
  • During tuber bulking and early senescence, naturally yellowing plants can look superficially similar to diseased plants. Context — comparing against the rest of the row — is essential.
  • Spunta's open canopy means individual sick plants are more isolated and visible against healthy neighbours. Fontane's dense canopy means a sick plant is more likely to be partially hidden by adjacent healthy plants.

The POTECTOR300 pre-selects images — every photograph it sends for annotation contains at least one plant showing symptoms. The machine makes the initial selection; the annotator's job is to identify exactly which plant is sick, how severe the symptoms are, and to draw a precise polygon around it. For that, knowing what a healthy potato looks like at full growth is the essential starting point.

Sources & further reading

  1. EOS Crop Intelligence. Potato Growth Stages: From Germination To Senescence. eos.com/crop-management-guide/potato-growth-stages/
  2. Wageningen University & Research. Augmented descriptions of growth and development stages of potato. research.wur.nl
  3. Wageningen University & Research. The life cycle of the potato (Solanum tuberosum L.). edepot.wur.nl/199013
  4. International Potato Center (CIP). Potato facts and figures. cipotato.org