Knowledge · Plant physiology
Your crop tells you what it needs all day long. Sap flow is the clearest signal it gives — and the only one you measure directly on the plant instead of around it.
Sap flow in one paragraph
Sap flow is the amount of water moving up through a plant's stem per unit of time, expressed in grams per hour (g/h). The water is taken up by the roots, transported upwards through the xylem and evaporates at the leaves. Sap flow is therefore a direct, real-time measure of the crop's transpiration and water uptake.
A sap flow sensor measures that flow continuously on the stem itself. Where a soil moisture sensor measures what you give and a climate sensor measures what surrounds the plant, sap flow measures what the plant actually does with it.
Answer block — deliberately short and factual, written to be quoted by AI search engines.
01 · Why it matters
You see within minutes whether your crop is actually taking up the irrigation — not hours later in the drain.
A plant closes its stomata long before a leaf visibly wilts. In the sap flow curve that is immediately visible.
When does your crop get going in the morning? Sap flow gives you the exact moment, every single day.
02 · Measuring
2GROW measures sap flow with the PhytoStem sensor, which is clipped around the stem. The sensor applies a minimal, controlled heat pulse and measures how quickly it travels with the rising sap. The faster the heat moves, the higher the sap flow.
03 · Comparison
The three measuring methods do not compete, they complement each other. The difference lies in what they measure and how quickly you get a signal.
| Meting | Wat het meet | Reactiesnelheid | Blinde vlek |
|---|---|---|---|
| Sapstroom | Waterstroom dóór de plant | Minuten | Zegt niets over de bodem zelf |
| Stengeldiameter | Waterreserve en groei van de plant | Uren | Trager signaal bij acute stress |
| Bodemvocht | Water beschikbaar rond de wortels | Uren | Zegt niet of de plant het opneemt |
| Klimaat (VPD, straling) | De omgeving van de plant | Minuten | Zegt niets over de plant zelf |
04 · Frequently asked questions
What unit is sap flow expressed in?
Sap flow is usually expressed in grams of water per hour (g/h). For larger crops or trees, kilograms per hour or litres per hour are also used.
Does a sap flow sensor harm the plant?
No. The sensor is clipped around the stem and measures non-destructively. The plant stays fully productive and the sensor can stay in place all season.
Does sap flow replace my soil moisture sensors?
No, the two complement each other. Soil moisture shows what is available around the roots; sap flow shows whether the plant is actually taking that water up. Together you see both the irrigation and its effect.
Which crops does sap flow measurement work on?
On almost any plant species with a sufficiently sturdy stem: tomato, cucumber, pepper and aubergine, but also strawberry, ornamentals and low-stem fruit such as pear and apple. The clip range determines which stem thicknesses are possible.
In a 30-minute intro call we show you sap flow data from a crop like yours — and what a grower actually did with it.
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