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Trees damaged by late season frosts can see negative impacts for years
Fri, May 09, 2025
Many trees in the Northern Hemisphere are leafing out earlier as the climate warms. But with leaves emerging earlier in the season, there is an increased risk of damage from a late spring frost. Researchers used experimental and observational data – including thousands of records from Nature’s Notebook – to evaluate the effects of late spring frosts on hundreds of tree species. The results indicated that late spring frosts have both short-term and long-term effects on tree growth and phenology. In the short-term, late spring frosts damage young leaves and limit tree growth that year. But more notably, late spring frost events also limit the amount of resources a tree can store that year, which results in delayed leaf emergence and reduced productivity the next calendar year. These results illustrate that the effects of extreme climate events on plant phenology and productivity may extend months, or years, into the future. The results may also help scientists generate more accurate predictions of how forests will respond to future climate change.
A more complete picture of the timing of spring
Thu, Mar 13, 2025
How early is spring this year and how does it compare to years past? We can answer this question using observations of plants and identifying the weather conditions that are needed for plants to leaf out and flower. For many years, the USA-NPN has shared maps, called the Spring Leaf Index and Spring Bloom Index, that show when weather conditions associated with events that signal the start of spring reached. However, an early start to spring does not necessarily mean that subsequent springtime events will also occur early. So, a team of researchers used thousands of observations submitted to Nature’s Notebook to identify conditions associated with events that occur later in the spring. And soon, maps for a Late Bloom Index, that depict the timing of activity in the latest-blooming plants will be added to the USA-NPN Status of Spring website. This new index, combined with the usual Spring Leaf and Spring Bloom Indices, will give us better understanding of how spring is progressing each year.
Phenology Week! March 17-21, 2025
Wed, Feb 12, 2025
March 17-21, 2025 is Phenology Week - a virtual celebration of the seasonal cycles of plants and animals. The purpose of Phenology Week is to celebrate YOU, our Nature's Notebook observers, Local Phenology Programs, and partners! We'll have webinars, awards, daily challenges, observer stories, and more.
Phenology Week Media Kit
Share Phenology Week Content on your social media! Our media kit contains daily activities to share with your community!