I just got one of these (3rd gen Spruce snsor) and it was a pain to pair (doesn't seem to pair to channels higher than 20 and the LEDs never seemed to do the exact pattern mentioned in the manual), but I finally got it to pair and reliably report. I probably wouldn't use Generic Zigbee Moisture sensor for this since that driver is intended for binary "wet/dry" sensors like water leak sensors. The native driver I had the best luck with was "Generic Zigbee Motion/Humidity" sensor. This was intended for the Iris v3 motion sensor that reports motion, temperature (which you'd still get from the moisture sensor), and humidity. Obviously the motion part goes unused, but I figured this would get me the closest I could with a native driver. So far, it does appear to be more or less working to some extent: it reliably reports temperature, and it reports...something for humidity (though extremely low values like 1.3% when in regular air; I haven't tried putting it in soil or water to see what it would read then).
There is a public ST DTH available: SmartThingsPublic/spruce-sensor.groovy at master · SmartThingsCommunity/SmartThingsPublic · GitHub. It looks like it just reports temperature and humidity, too, and it probably doesn't do much fancy calculation with the humidity (just seems to round the raw value, though I can't see what that actually is...presumably what the generic driver reports, too). Someone in this thread claims to be using a custom driver from Mike or ihiyardi for the v1 sensor (probably not too different?), but I can't find that anywhere publicly and the poster never responded to someone who asked about it.
In any case, we'll see how it goes once I put it outside, I guess.
