California Crop Stress Index

SWP (Stem Water Potential) measures how hard a tree is working to pull water from the soil. It's measured in bars of negative pressure. More negative = more stress.

Most of this page is in Δbar, which is how far a block reads below the fully-watered baseline for that day's weather, the reading a tree with all the water it wanted would give. We write it as a negative number, the same direction as SWP itself. Thresholds vary by crop and by growth stage. The index counts almond, prune and grape blocks as past the irrigation trigger at 8 bars below baseline, which in summer weather is a stem water potential near -14 to -18 bar. Wine grapes are often held drier than that on purpose during ripening. The trend over the weeks matters as much as the level.

As a general guide: readings near -3 to -6 bar indicate low stress (well-watered), -10 to -14 bar moderate stress (irrigation timing matters), and beyond -16 bar high stress where yield impact is likely.

7-day outlook. Under a crop's trend, the outlook is the forecast FloraPulse serves to each grower for their own blocks — a model trained on this network's seasons and driven by the weather forecast — averaged over the blocks that have one. It assumes no block is irrigated, the fan a grower sees before deciding whether to water, so it reads as the pull of the week ahead, not a prediction of next week's index: blocks that are irrigated land above the line. The line starts from each block's own reading on the day its forecast was issued; the shading is a typical block's 10–90% range, and the share past the trigger uses the same flat trigger as the panel below. A crop shows an outlook when it has a served model and five or more blocks with a full seven-day forecast: see each crop's card.

How this differs from satellite or ET-based tools. Weather models and satellite imagery estimate what plants should need from air temperature, humidity and canopy reflectance. FloraPulse microtensiometers measure the water pressure inside the trunk. Two orchards with identical weather can read very differently because of soil type, rootstock, tree age and irrigation system efficiency, and the sensor sees that where a model cannot. How the sensor works.