March
by Master Naturalist Pam Johnson.
Last month we explored trees by observing bark and leaf scars. This month we will explore buds forming and flowers starting to bloom – springtime indicators. The natural world is waking up and birds are beginning their migration. I am antsy to get out and explore. JDCF will be holding a Community Science Workshop at Mąą Pįį on March 14th. The morning workshop will focus on Bluebird house monitoring and the afternoon workshop on Nature Apps (iNaturalist, Merlin and eBird). We can practice these Apps on the property. I noticed the first Bluebird on Feb 12th so the Bluebird box portion in the morning should see some bird activity.
When I was first getting interested in the natural world of Jo Daviess County, someone suggested I might want to help track the seasonal tree events with National Phenology Network (NPN). It seemed like something I could do in my own yard. Phenology is nature’s calendar—when cherry trees bloom, when a robin builds its nest and when leaves turn color in the fall. Phenology is vital to many aspects of ecology and society. Phenology is also a leading indicator of climate change. With climate change, we’re not just seeing changes in average temperature and rainfall, we are also seeing an increase in the frequency of extreme weather events. “Phenology” refers to when recurring seasonal events occur, it’s all about timing.
Why track phenology? Scientists must explore the potential effects of extreme weather events on the timing of plant and animal life stages. To address this question, a group of researchers used more than 2 million observations of plants, butterflies, and moths in the U.S. that were submitted to iNaturalist between 2016 and 2022. They used this data to determine whether the start and end of plant flowering periods and insect flight periods were affected by extreme heat, extreme cold, extreme dry, or extreme wet conditions. Extreme cold led to earlier insect activity and longer flight periods but did not affect plant flowering. And finally, extreme wet or dry conditions delayed both the start and the end of plant flowering and insect flight periods.
Migrating birds are also affected by when plants leaf out making insect food available. According to Teressa Crimmins in her book Phenology, “It gets even more complicated. In the Northern Hemisphere, the pace at which plants are undergoing leaf out across the country from south to north is also increasing. What this means is that the number of days that pass between when plants leaf out in Georgia and when plants leaf out in Maine is shorter than it used to be. The implication is that all birds migrating north across the United States – regardless of whether they are migrating from the Southern Hemisphere or from the southern United States – must move more quickly to keep pace with food availability along the migration route and arrive at the breeding grounds when food is available.” Short-distance migrants cue their migration on temperature and long-distance migrants cue their migration on day length. Short-distance migrants must speed up the journey. Long-distance migrants may not be keeping up with the changes.
March Phenology to look for on JDCF preserves (you might start your own calendar of events)
Amphibians
Frogs begin calling
Snakes begin to emerge
Box Turtles, Snapping Turtles, Map Turtles coming out of brumation (turtle hibernation)
Birds
Turkey vultures arrive
Tree swallows arrive
Eastern Phoebes arrive
Great blue herons arrive
Kildeers arrive
Bluebirds arrived in Feb staking out nest sites
Flowers
Bloodroot and sharp-lobed hepatica begin to bloom
Dutchman’s breeches begin to bloom
Spring beauty begins to bloom
Canadian Wild Ginger begins to bloom
Trees/Shrubs
Serviceberry begins to bloom
American Plum begins to bloom
Eastern Redbud begins to bloom
Red Maple begins to bloom
Missouri Wild gooseberry begins to bloom
“Through regularly visiting plants and animals in your yard [or JDCF properties] and documenting what you see might not feel like much, the action can contribute valuable information to support scientific discovery as well as reorient your heart and mind in a way that other efforts cannot. This small step may be the most important one you can take, for yourself and the planet.” (Theresa Crimmins, Phenology)
Resources:
Coincide by Don Orton
Phenology by Theresa M. Crimmins
There are practical uses for landscape stewards and gardeners in understanding insect and plant phenology events. When I took classes in pest and disease management, I learned about the relationship between when a certain plant blooms (indicator plant) and when an insect emerges. I found this relationship fascinating and useful in managing my own landscape. That relationship is based on accumulated heat measured by growing degree days (GDD).
The development of plants, insects and fungi is dependent on heat. Development speeds up as the temperature increases and slows as temperature decreases. Many plants and insects have been studied in regard to this relationship between heat and development. We can anticipate the flowering of a shrub or the emergence of an insect based on how many growing degree days (units of heat, not actual days) have accumulated.
The Morton Arboretum’s Plant Health Care Report (PHCR) provides a weekly, seasonal newsletter providing crucial, science-based information on pest emergence, disease, weather data, and plant phenology in Northeastern Illinois. It includes Growing Degree Days (GDD), in-bloom indicators, and management tips for gardeners and professionals. I use the information posted for Rockford.
Here is one way to calculate GDD. Add the maximum temperature to the minimum temperature for any given day. Divide by two to get the average temperature for that day. Now subtract 50 ( a commonly used base number for these calculations). If the number resulting from this calculation is above zero, then that is the number of degree days for that day. If the result is zero or below, then the number of GDD is zero for that day. When we have accumulated 100 GDD, we expect certain insects to begin emerging and certain plants to be in flower. The Morton’s Plant Clinic does this for us yearly.
Here is an example: Between 100 and 200 GDD50, we can expect to see Eastern tent caterpillars emerging from their eggs. At that same number of GDD we will also see redbud (Cercis canadensis) beginning to flower. The redbud can be used as an indicator plant. Its early flowering stage indicates that we have had enough GDD to cause the Eastern tent caterpillars to hatch out. Now we know when to look for them. The redbud, and other indicator plants, are good visual cues for GDD that are easy to spot in the landscape.
This allows landscape managers and landowners to target the specific pest at a specific time minimizing the use of pesticides. This was called Integrated Pest Management (IPM). Knowledge of which pest is really destructive and needs management is also important to IPM. Morton Arboretum’s website provides weekly information during the growing season (Plant Health Care Report ).
Example: April 2024 Plant Health Care Report
NPN keeps track of locations to produce a graph of how GDD is changing from one year to the next. Sample graph for Galena comparing 2025 (blue) and 30-year average (black).
Reference: NPN Visualization Tool
Northern leopard frog
Spring beauty
Turtle
