How do I know when to start and stop reporting yes to a phenophase?

Tips for Backyard Observers

We asked backyard observers what questions or challenges they are having when observing. We then put together an Observer Tip Sheet that addresses every issue you bought up. You can access the full tip sheet here. But today, we wanted to highlight one specific question...

How do I know when to start and stop reporting yes to a phenophase?

Certain phenophases can be especially difficult to spot when they first begin or might be challenging to know when then are over. Take the "breaking leaf buds" phenophase for an example. It starts when the first bud shows a green tip as the new leaf begins to emerge. It ends once a leaf has fully emerged from the bud. This phenophase is a challenge both because the change from dormant bud to active swelling bud to leaf emergence is subtle and also because it can be difficult to judge exactly when the leaf has fully emerged.

Reading the phenophase definitions carefully can help. The definitions have clues to help you know when to start and stop. We created this handy sheet with start and stop cues for each phenophase to help you out. You can also find it on the resources page of our website.

Another great resource to consult when you are not sure about the endpoints of a phenophase is the Phenophase Primer created by the USA-NPN. The Primer discusses each phenophase in depth along with supporting pictures.

As is always the case, this becomes easier with practice. Taking our "breaking leaf buds" example, if you watch a few buds make the full transformation from dormant to full leaf emergence, you will be able to better judge whether it looks like any particular bud is still in the breaking stage. I also find that coming back the next day can help. The little bit of growth that occurs from one day to the next often is enough to help me be certain that, for instance, a leaf has fully emerged from the bud and that the breaking leaf bud stage is over.

Most importantly, don't stress over it. Make your best guess. You can go back and correct errors later.