I have some experience in phenological observations with the Wingscapes PlantCam and some other (self-built) automatic camera setups. I think you'll first have to decide at which level you want to observe phenology. Bud development can be tracked on individual twigs, which gets you high resolution phenology data and allows other measurements as well, e.g. extension growth. However, the downside of this approach is, that you'll would need many cameras to obtain an acceptable replication. With less cameras, you can track the rough phenology on stand level (you will be able to detect general leaf-out (greening), although it's harder for evergreen species), however the extraction of these dates from your image timeseries (through Vegetation Indices such as ExG,...) will require some more image processing and different light conditions may have a stronger effect on the images. Some calibration of your system with visual observations has to be done anyhow.

The most appropriate setup for project further depends on the technical connections (power, internet,...) you'll have available at your field site and your budget: The possibilities range from weatherproof DSLR (check out CHDK for timelapse with Canon cameras) to webcams to autonomous battery-powered cameras (such as the TimelapseCam).

I'm looking for someone who has tried to do such a thing

Lahcen, perhaps follow the lead of the phenocam network started by Andrew Richardson at Harvard http://phenocam.sr.unh.edu/webcam/. You could use similar methods with much cheaper web camera. Hope this is helpful, good luck.

Yep - definitely check out Andrew Richardson's work on the subject.

Yes, I agree with Martin. The temperature differences should mark the budding trees

I have used "TimelapseCam" from Wingscapes (wingscapes.com, 888-811-WING) for extended time lapse photograph over periods of several months in very harsh conditions (temperature extremes, high wind and a desert environment) with good success

Thank you for yours help very informatives.

You could also try a trail camera that is used to take pictures of deer and wild animals. The cameras are very rugged and are in a weather proof box

To establish a video ("TimelapseCam" from Wingscapes (wingscapes.com, 888-811-WING)) or old cinemacamera on the smallest speed on a support or to photograph through set time. To put seeds and sund between 2 glasses (the gap between glasses has to be the size of the grain) in darkness for 2 days and to open only for the period of shooting, and then when there will be shoots as usual.

I have some experience in phenological observations with the Wingscapes PlantCam and some other (self-built) automatic camera setups. I think you'll first have to decide at which level you want to observe phenology. Bud development can be tracked on individual twigs, which gets you high resolution phenology data and allows other measurements as well, e.g. extension growth. However, the downside of this approach is, that you'll would need many cameras to obtain an acceptable replication. With less cameras, you can track the rough phenology on stand level (you will be able to detect general leaf-out (greening), although it's harder for evergreen species), however the extraction of these dates from your image timeseries (through Vegetation Indices such as ExG,...) will require some more image processing and different light conditions may have a stronger effect on the images. Some calibration of your system with visual observations has to be done anyhow.

The most appropriate setup for project further depends on the technical connections (power, internet,...) you'll have available at your field site and your budget: The possibilities range from weatherproof DSLR (check out CHDK for timelapse with Canon cameras) to webcams to autonomous battery-powered cameras (such as the TimelapseCam).