Project Overview:

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We invite you to join us in tracking the “green wave”—the flush of green that accompanies leaf-out—over the course of the spring season, as well as the spread of seasonal color across the country in the autumn.

Observations of these trees are of extra importance because they can help decision-makers develop forecast models and early warning systems for use in forest management and public health administration via pollen forecasting. In fact, researchers are already using data that have been reported for these species to validate models that predict how changes in climate will impact phenology of trees, and also to learn that deciduous trees may leaf out weeks earlier under climate warming

Join us for this special campaign! Make it easy on yourself - choose that tree that you see every day, either the one in your yard or the one you pass each day. Observations from just one tree can help fill critical data gaps!

See what we learned from this campaign in 2023


You will receive messages full of findings, observation tips, and campaign-specific opportunities. Don't miss out!


1. Join Nature's Notebook. If you haven't already, create a Nature's Notebook account. If you need more details on getting started, take the Observer Certification Course at

2. Select one (or more) individual maple, oak, or poplar trees to track from the list below, and add it to your site.

boxelder (Acer negundo)*
red maple (Acer rubrum)*
sugar maple (Acer saccharum)*
vine maple (Acer circinatum)*
bigleaf maple (Acer macrophyllum)
bigtooth maple (Acer grandidentatum)
mountain maple (Acer spicatum)
Norway maple (Acer platanoides)
Rocky Mountain maple (Acer glabrum)
silver maple (Acer saccharinum)
striped maple (Acer pensylvanicum)
sycamore maple (Acer pseudoplatanus)

laurel oak (Quercus laurifolia)*
Oregon white oak (Quercus garryana)*
northern red oak (Quercus rubra)*
Arizona white oak (Quercus arizonica)
bear oak (Quercus ilicifolia)
black oak (Quercus velutina)
blue oak (Quercus douglasii)
bur oak (Quercus macrocarpa)
California black oak (Quercus kelloggii)
California live oak (Quercus agrifolia)
chestnut oak (Quercus montana)
Emory oak (Quercus emoryi)
Gambel oak (Quercus gambelii)
huckleberry oak (Quercus vacciniifolia)
live oak (Quercus virginiana)
pin oak (Quercus palustris)
sand live oak (Quercus geminata)
shingle oak (Quercus imbricaria)
Shumard's oak (Quercus shumardii)
southern red oak (Quercus falcata)
turkey oak (Quercus laevis)
valley oak (Quercus lobata)
white oak (Quercus alba)
willow oak (Quercus phellos)

balsam poplar (Populus balsamifera)*
Eastern cottonwood (Populus deltoides)*
Fremont cottonwood (Populus fremontii)*
quaking aspen (Populus tremuloides)*
bigtooth aspen (Populus grandidentata)
blck cottonwood (Populus trichocarpa)
narrowleaf cottonwood (Populus angustifolia)

*Due to their geographic spread, these species are of special interest. 

3Take observations. We invite you to track your trees ideally 2-4 times a week, in the spring and autumn. We are especially interested in the phenophases below, though you are welcome to report on flowering and fruiting as well.

4. Report your observations. As you collect data during the season, log in to your Nature's Notebook account and enter the observation data you recorded. You can also use the Nature's Notebook app to submit your observations! 

Phenophase Definition Photo (click to enlarge)
Breaking leaf buds One or more breaking leaf buds are visible on the plant. A leaf bud is considered "breaking" once a green leaf tip is visible at the end of the bud, but before the first leaf from the bud has unfolded to expose the leaf base at its point of attachment to the leaf stalk (petiole) or stem. For Acer rubrum, leaf tips may appear reddish.  Red maple breaking leaf buds, Photo: Ellen G Denny
Leaves One or more live, unfolded leaves are visible on the plant. A leaf is considered "unfolded" once its entire length has emerged from a breaking bud, stem node or growing stem tip, so that the leaf base is visible at its point of attachment to the leaf stalk (petiole) or stem. Do not include fully dried or dead leaves.  Red maple leaves, Photo: Ellen G Denny
Increasing leaf size A majority of leaves on the plant have not yet reached their full size and are still growing larger. Do not include new leaves that continue to emerge at the ends of elongating stems throughout the growing season.  Sugar maple increasing leaf size, Photo: Ellen G Denny
Colored leaves One or more leaves (including any that have recently fallen from the plant) have turned to their late-season colors. Do not include fully dried or dead leaves that remain on the plant.  Colored Leaves, Maple, Photo: Ellen G Denny
Falling leaves One or more leaves are falling or have recently fallen from the plant. Not pictured


You can earn this badge by making six observations of one target Green wave species within the same year. See it on your Observation Deck.

See it on your Observation Deck.

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