What Is Phenology: Information On Phenology In Gardens

What Is Phenology: Information On Phenology In Gardens

Many gardeners start planning the successive garden almost before the first leaf turns and certainly before the first frost. A walk through the garden, however, provides us with our most valuable clues as to the timing of various crops. Climate, weather and temperature triggers interact with the environment and impact the plant, animal and insect worlds – phenology. What is phenology and how can practicing phenology in gardens help us to correctly time planting and fertilizing? Let’s learn more.

What is Phenology?

Everything in nature is the result of phenology. Granted, human involvement and natural disasters can alter the natural order of phenology but, generally speaking, organisms, including human beings, rely on and act according to the predictable nature of seasonal changes.

Modern phenology began in 1736 with the observations of English naturalist Rober Marsham. His records of the connections between natural and seasonal occurrences began that year and spanned another 60 years. Some years later, a Belgian botanist, Charles Morren, gave the phenomenon its official name of phenology deriving from the Greek “phaino,” meaning to appear or to come into view, and “logo,” to study. Today, the phenology of plants is studied in many universities.

How can phenology of plants and other creatures help us in the garden? Read on to find out about penology garden info and how to incorporate its use in your landscape.

Phenology Garden Info

Gardeners generally like to be outside and, as such, are often keen observers of the cycles of nature. The activities of birds and insects let us know that spring has arrived even if the sun isn’t really shining and the forecast is for rain. Birds inherently know that it is time to build a nest. The early spring bulbs know that it is time to emerge, as do the overwintering insects.

Climatic changes, like global warming, have made phonological events occur earlier than usual causing changes in bird migrations and early flowering, hence, my early allergies. Spring is arriving earlier in the calendar year and fall is beginning later. Some species are more adaptable to these changes (humans) and others are affected more by them. This results in a dichotomy in nature. How organisms react to these changes makes phenology a barometer of climate change and its impact.

Observation of these naturally reoccurring cycles can help the gardener too. Farmers have long used phenology, even before they had a name for it, to pinpoint when to sow their crops and fertilize them. Today, the lifecycle of the lilac is commonly used as a guide to garden planning and planting. From leafing out to the progression of the blossoms from bud to fade, are clues to the phenology gardener. An example of this is the timing of certain crops. By observing lilacs, phenologist have decided that it is safe to plant tender crops like beans, cucumbers and squash when the lilac is in full bloom.

When using lilacs as a guide to gardening, be aware that phonological events progress from west to east and south to north. This is called ‘Hopkin’s Rule’ and means that these events are delayed 4 days per degree of north latitude and 1 ¼ days per day of east longitude. This isn’t a hard and fast rule, it’s meant to be a guideline only. Altitude and topography of your area may affect the natural events indicated by this rule.

Phenology in Gardens

Using lilac’s life cycle as a guide to planting times yields much more information than when to plant cukes, beans and squash. All of the following can be planted when the lilac is in first leaf and dandelions are in full bloom:

  • Beets
  • Broccoli
  • Brussels sprouts
  • Carrots
  • Cabbage
  • Collard greens
  • Lettuce
  • Spinach
  • Potatoes

Early bulbs, such as daffodils, indicate planting time for peas. Late spring bulbs, like irises and daylilies, herald planting times for eggplant, melon, peppers, and tomatoes. Other blossoms signify planting times for other crops. For example, plant corn when the apple blossoms begin to fall or when the oak leaves are still small. Hardy crops can be planted when the plum and peach trees are in full bloom.

Phenology can also help pinpoint when to watch out and manage insect pests. For example:

  • Apple maggot moths peak when Canada thistle blooms.
  • Mexican bean beetle larvae begin munching away when foxglove blossoms.
  • Cabbage root maggots are present when wild rocket is in flower.
  • Japanese beetles appear when morning glory starts to grow.
  • Chicory blossoms herald squash vine borers.
  • Crabapple buds mean tent caterpillars.

Most events in nature are the result of timing. Phenology seeks to identify the clues that precipitate these events that affect the numbers, distribution and diversity of organisms, the ecosystem, food surplus or loss, and carbon and water cycles.

Phenology: telling time by nature’s clock, with cary institute

I T’S ALL CONNECTED OUTDOORS, and the science of phenology can help us understand exactly how. Called “nature’s clock,” or “nature’s calendar,” phenology is the study of recurring life-cycle stages among plants and animals, and of their timing and relationships with weather and climate. So not just “the peepers peeped today” (like the one not peeping, above, on a leaf in my garden), but the whole intricate picture outside at a given time.

By putting it all together, scientists can gain a better understanding of an entire ecosystem’s intimate interactions–providing a critical view into the effects of a changing climate. But they need our help, gardeners–and learning to be more objective, keener observers can open a whole world of smaller “aha’s” up to each of us, too.

I got a lesson in phenology from Victoria Kelly, Environmental Monitoring Program Manager at the Cary Institute of Ecosystem Studies in Millbrook, New York, not far from my garden or from Robin Hood Radio, the NPR affiliate where my show is created each week. Environmental Monitoring is a longterm program at Cary, begun in the 1980s and designed specifically to monitor climate—and the air, precipitation and water chemistry.

Now Cary is adding biological monitoring to the effort, by establishing a “phenology trail” on the grounds of the not-for-profit environmental research organization, whose team of scientists look at the ways different phenomena interact, and the effect on nature. The trail is part of a nationwide network of collaborations with the USA National Phenology Network.

Around the country, citizen-science volunteers are being recruited to join in making observations. Not just scientists, who cannot possibly record all the needed data themselves, but also educators and students, nonprofits and NGOs and Native American tribes and clubs and others—amateur and professional naturalists alike—will observe and record what happens when. The 2015 nationwide goal: 1.5 million phenological observation records. [Update: In 2016, 2.4 million observations were recorded.]

Whether you officially help or not, phenology is fascinating–and already Cary scientists have some predictions to make about creatures as welcome as the peepers, or disliked as black-legged ticks. Read along to my conversation with Victoria as you listen to the March 9, 2015 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).

Plus: Readers nearby Millbrook, New York, can contact her anytime about helping with the phenology project.

Listen/read: phenology q&a with cary’s victoria kelly

Q. Can you give some examples of the kinds of interactions that you focus on, Vicky, and why you look for what you look for?

A. It’s pretty simple: We’re looking at things like when do the trees leaf out, when do the flowers come out? We’ll be asking people who volunteer to actually note the dates these things are observed, because as the climate changes, we expect that some of these occurrences will shift with these changes—and that can wreak havoc.

Some of your gardener listeners might remember times when the apples and other fruit trees blossomed and then a hard frost happened, for instance. They blossomed because the temperature warmed up, forcing the blossoms open, but then the freeze came. The same kind of thing can happen to trees and other plants in nature, so we wonder if the climate as it changes is going to result in more of this happening. We really need to monitor this—actually take data on a yearly basis to predict it and understand it.

Q. We might note that a particular tree—whether native or a specimen in a garden—like, for instance, the shadbush or serviceberry (Amelanchier), which blooms at the forest edges early in the season. So you’d note that, and then you’d also note what else was happening?

A. We’ll be using the framework of the National Phenology Network, and they have forms, which ask questions of the observers: Do you see leaves? Do you see breaking buds? Are they flower buds? Do you see seeds?

We’ll be monitoring all kinds of phenophases of these plants—the switch from one phase to another. In addition, we’ll be asking observers to note if they see insects, and animals—specific kinds of insects and animals: different kinds of butterflies, frogs, newts, turtles, birds. That’s going to give us an idea of when those phenophases happen with the plants, and whether they co-occur with the arrival or presence of different animals that may use those plants .

Q. As a host plant, or to gather pollen or nectar from, for instance.

So this is different from degree days, isn’t it?

A. Degree days is a measure of temperature a measure of cumulative temperature. It’s an index that can be used to predict when a phenophase might occur, or an insect might emerge. But it’s essentially just a measure of temperature.

Q. So at a certain number of degree days, that may precipitate one of these phenophases.

A. Correct. Usually what happens is that you calculate degree days, and at a specific number, a leaf might emerge, or an insect might appear. We expect that the date at which that number happens is going to shift with climate change.

Q. I read a 2013 research paper at the Cary Institute website on when the peepers peep each year, written by a colleague of yours, Gary Lovett. Over the 15 years of record, the DFC or date of first calling was never the same.

A. That paper showed that the peepers’ date of first calling got earlier and earlier of that 15 year period. He’s able to estimate when the peepers will peep, based on that degree day number.

Q. So there can be a sort of forecasting…

A. Right, you can predict the date.

Q. In the 15 years of data, there were dates of first calling as varied as about a month, from 9 March to as late as 4 April in different years studied.

A. These organisms, like the peepers, have evolved to become active during a specific period of time. Usually the triggers for becoming active are based on daylength, not temperature, but sometimes temperature can force things. What we’re concerned about is that with climate change, we’ll see—like we have with the peepers—early activity, but then a late frost can really do some damage.

So again: We’re embarking on this program to really collect the data to know if this is happening, and to what extent.

Q. Some gardening friends say—and this is where these more folksy versions of phenology come in, or maybe what you could call conventional wisdoms—they say such things as “prune roses when the forsythia blooms,” and “look for Eastern tent caterpillars at crabapple bud break” if you want to get rid of them. As far as the peppers go: “Plant peas when the peppers peep” is another one. Are they on to anything, and can such correlations and inferences be made?

A. They do make some sense sometimes biologically, and we can glean a lot of information from those folk wisdoms of the ages. But what we’re really looking for at this point are some numbers to back up those folk tales. The way to do that is to go out and collect the data—to note the dates that things occur.

Those folk tales are based on what has occurred over the ages, but things have changed. They may have worked in the past—but we’re not sure they’ll continue to work.

Q. Tell us about some of the other projects at Cary, like the one studying peepers.

A. There are a lot of them. There is work that Rick Ostfeld [above, making observations], who’s a disease ecologist at Cary, has recently published about activity level of ticks. We used to call May “Lyme Disease Awareness Month,” and he is suggesting that we shift that to April, because of the change in activity level. So there are all kinds of applications for this kind of work.

We’ve been studying all kinds of systems, but this will be the first time that we’re setting out to collect data in an organized way about the phenology of plants in a specific place here at Cary. This study of phenology is a new and developing research area, and it’s turning out to be a promising development for ecology.

Q. And the new project this year at Cary that you’re recruiting helpers for the phenology trail? What’s the goal there?

A. The program that I have just set up is the Fern Glen Phenology Trail. There are about 20 marked plants in our beautiful, enchanting Fern Glen here at the Institute.

It’s a small parcel of land with little trails and boardwalks and a deck that overlooks the creek. We’re asking citizen-science volunteers to visit those marked plants and to answer questions about what they observe.

They’ll collect data—their observations—about whether they see leaves, flowers, fruit, and how many of each. We’ll be able to tell when leaves first emerged, or the flowers finished. We hope to be able to collect these data over a long period of time—decades—so we can evaluate the effects of climate change and other factors on the organisms that we share this planet with.

Q. You already know the plant palette and the animals of this area of the Institute, so besides ferns, what else is in the Fern Glen?

A. It was a garden at one time, and is still maintained sort of as a rough garden. A lot of native plants have been planted there–bluebead [Clintonia borealis], hepaticas, trilliums, jewelweed, among others. We’ve selected a group of plants to study that are representative of a range of types of plants and of a range of timing in emergence, flowering, fruiting.

So, for example, we’ve marked red maples, witch-hazels and spicebush—as well as the forbs. [Above, left to right, spicebush and hepatica blooms at Cary.]

Q. Spicebush is one of my favorite woody plants, and I think it’s underappreciated by gardeners. Wonderful—and important, too, because it blooms so, so early, providing the first insects with sustenance. [Blooms in Margaret’s garden, below.]

A. It’s a very interesting plant, and you’re right: It’s one of the first bloomers. There is a long period of time to observe spicebush. It blooms very early, it develops leaves, and it sets fruit in late October into November—a really interesting plant.

Q. Lindera benzoin. And since so many listeners are gardeners, I want to add that it’s also a beautiful large shrub that can grow at the woodland edge, with a great architecture: multistemmed and low-breaking. And the yellow fall color is exceptional. I rarely get to see the fruit for long—the local critters seem to know, “Margaret’s got spicebush fruit. Let’s go get it.”

A. The red fruit is beautiful, and spicebush is easy to grow—plus a swallowtail butterfly requires the spicebush for reproduction. We have lots of it in the Fern Glen, and will be observing its phenophases over a long period of time, hopefully.

Q. So to reiterate for those listening elsewhere, this Fern Glen Phenology Trail is just one undertaking—which happens to be near me—in a nationwide effort by the National Phenology Network. Their Nature’s Notebook national online program of recording data has set a goal to collect 1.5 million observation records in 2015. Schools, for example, or other groups can start a program, or join an existing program.

A. We’re part of the national program, and we’re also part of a regional program. The Environmental Monitoring & Management Alliance is a group of about eight sites along the Hudson River, from the New York Botanical Garden to the Huyck Preserve—including the Mohonk Preserve, and Vassar College Preserve and others. And there is also the New York Phenology Project—all parts of this bigger endeavor by the national network.

There are phenology trails all over the country.

[Individuals anywhere can register to join an existing project, or even get set up to observe in their own backyards at the national Nature’s Notebook online program.]

Q. It’s so interesting: If the observations many of us may have thought of as folksy gardening wisdom are made in a more objective manner, with more of a scientist’s eye, they can really make such a difference in a much more pressing issue at hand, such as a changing climate.

A. We can get so much more with the help of citizen scientists than we can on our own.

Learn more about the cary programs

  • The Cary Institute website
  • Contact Victoria Kelly at Cary about the overall program
  • The latest from tick research at Cary Institute

Prefer the podcast version of the show?

M Y WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its seventh year in March 2016. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the March 9, 2015 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).

(Photos of Cary Institute from Cary website used with permission. Peeper and Lindera photos by A Way to Garden.)

Community Science: Garden Phenology Walk

California Entrance Garden

New Sessions just added for Fall (see more details below).
Space is limited, advanced registration is recommended.
Free with $5.00 general admission to the Arboretum UCSC students & Members are free.
Study the science of the seasons: be a part of a national effort to monitor the effects of climate change.

Phenology: nature’s calendar - phenology is the timing of life cycle events, for example: when plants first bloom, birds migrate, and insects hatch.

Monitoring phenology is important: changing phenology is a key indicator of climate change. It is a hot topic in climate change research. You may have even observed phenology change without realizing it, like if you noticed plants in your garden blooming earlier during warm years.

YOU can collect phenology data and contribute to climate change research: The Garden Phenology Walk gathers data on seasonal changes in plants including when they leaf out, flower and form fruit. Help us monitor 18 permanently marked California native plants while touring the beautiful Native Plant Garden. Your data will be uploaded to the USA National Phenology Network’s (link to USANPN) database for use in research, policy and land management.

Help us collect data: Come to a workshop: Phenology researcher Karen Tanner provides hands-on data collection training.

Note: New time slot for sessions. Space is limited, advanced registration is recommmended.


Collect data during your own visit to the Arboretum:

Pick up a booklet, map and data sheets (words are links to .pdf files) at the entrance to the Native Plant Garden. Collect data by following the instructions in the booklet. Fill out the datasheets and drop them in the dropbox at the entrance to the Native Plant Garden. Please return the booklets and maps so other people can help us collect data too!

Q: What is the USA-National Phenology Network?

A: The USA-NPN is an organization that develops standardized protocols for collecting phenology data. Then, researchers, students, volunteers, and community scientists use these protocols to collect phenology data all across the USA. This data is managed by the USA-NPN and is used by researchers, land managers, and policy makers. Also, all the data is available to the public. Visit for more information.

Q: Why is it important to monitor the same individuals and plots from year to year?

A: By monitoring the same individuals and plots from year to year we can assume that any phenological changes we observe are due to environmental change over time, and NOT due to the location or genetics of the plants.

Q: Why monitor multiple individuals for each species?

A: Scientists require replication to ensure results are consistent. This also accounts for differences due to the locations of the plants.

Q: Why monitor species year-round, even when they are dead or dormant?

A: This is important information too! It provides information about the length of the growing season, like whether plants are dying earlier in the season, or if the dormancy period is longer.

Q: I am using the Nature’s Notebook app and see that some phenophases are not included in the booklet and datasheets provided by the UCSC Arboretum. Why are some phenophases included, but not others?

A: We only included the phenophases that we thought were unambiguous and simplest to record data for. However, if you want to record all the phenophases in your Nature’s Notebook account, please feel free to do so.

What is Phenology?

Phenology is the study of the timing of nature’s cyclical events, such as the emergence of leaves and flowers, bird migration and nesting, and animal hibernation. Scientists are particularly interested in how these are related to seasons and climate. Phenology is derived from Greek, and means “the study of appearance.” You do not have to be a scientist to make phenological observations, and there are plenty of tools to help you learn more. Phenology is a good way to engage youth in scientific observations without making special arrangements or using fancy equipment.

Observing nature is a lost art in our busy world, so take advantage of this pause in activity to sharpen this basic skill. Even young children can take notes, make sketches or take pictures of phenological phenomena. Be sure to record the date of your observation, and make notes on the weather conditions at the time, such as temperature, precipitation or wind patterns. These can easily be seen on a smart phone’s weather app.

Plants make a great subject to study, as they are easy to observe and cannot move away, as animals can. One does not need to go far to get started. In fact, starting in one’s yard or neighborhood makes it more likely that one will make routine observations without a special trip. Select a few plants, and start keeping a record in a notebook. Look for signs of change, such as the emergence of new leaves or the first hint that flower buds are about to open. Record how long a flower remains open, and keep a list of pollinators that come to visit. Later in the year, look for signs that fruits and seeds are forming. Keep observing the same plant over several years, and patterns will start to emerge.

Looking to learn more? The USA National Phenology Network is a unique resource for those who want to explore data. The website shows the arrival of spring leaf out, start and end of the growing season, the emergence of caterpillars and much more. You can go a step further and submit your own observations by visiting Nature’s Notebook, a citizen science project. Citizen science projects are a chance for the public to join other amateur observers and help build a rich resource that is used by scientists to study natural phenomena. This is a great option for educators and parents looking to engage students in science outside of school. Get outdoors and start observing!


The calendar says that spring is officially here, but it doesn’t really look like it yet. Today’s tip touches on a branch of science called phenology, meaning when climatic conditions correlate with plant and animal behaviors. Some say spring has arrived when you spy a robin. I say it doesn’t start until certain plants are “springing” back to life.

The first tree that truly symbolizes spring for me is the Amelanchier. Did you know that Amelanchier trees are sometimes called Serviceberries because in the olden days, winter snows would prevent travel on roads? Once the Serviceberries were in bloom, settlers knew the roads would be passable and preachers could finally travel to perform services like weddings and funerals.

When the flowers open on an Apple Serviceberry you’ll know that warmer days are here to stay and birds will be swooping in to eat the insects that are attracted to them.

Finally, Corneliancherry Dogwoods aren’t easily fooled by a few warm days. When the bright yellow clusters of flowers are peeking through the buds, I know spring is a sure thing.

It’s a fun activity to keep a garden journal documenting these changes in nature.

Welcome to our week-by-week (during the growing season) account of the findings in the Phenology Garden at Lake Park. This garden is tended and monitored by Coshocton County OSU Extension Master Gardener Volunteers as part of their ongoing education and training, as well as, gathering and entering data for both the OSU Bee Lab and the Ohio Phenology Calendar.

2019 Phenology Updates
February 19 March 11 March 25 April 8 April 15
April 22 April 29 May 6 May 13 May 20
May 27 June 3 June 10 June 17 June 24
July 1 July 15 July 23

2018 Phenology Updates
March 7 March 14 March 21 March 28
April 3 April 10 April 17 April 24
May 1 May 8 May 15 May 22 May 29
June 5 June 12 June 19 June 26
July 3 July 10 July 17 July 24 July 31
August 7 August 14 August 21 August 28
September 4 September 11 September 18 September 25
October 3 October 10 October 17 October 24

2016 Phenology Updates
March 18 March 25
April 8 April 15 April 22 April 29
May 6 May 13 May 20 May 27
June 3 June 10

The study of recurring, seasonal biological events and their relation to weather. Examples of such phenological events include bird migration, autumn leaf color, insect emergence, and budburst.

How Do We Use Phenology?

Phenology is one of the oldest sciences. Hunter-gather societies use the knowledge of seasonal events to plan when fruits and berries ripen and to predict when animals migrate for hunting.

We can use phenology to study climate change by documenting the start of spring and fall over the decades. We also use plant phenology to help predict pest emergence because both plant and insect development is temperature-dependent. Phenology can also helps us to design gardens with season-long interest.

The Pollinator Phenology Research in Coshocton County

Phenology and Climate Change

The impact of climate change can be analyzed by studying phenological change. Flowers bloom earlier, animals migrate off-schedule, autumn leaves fall later in the season — while these sometimes seem like harmless occurrences, they may lead to problems in species that have a domino effect on the rest of the ecosystem.

As plants and animals respond to climate change, their habit changes impact the resources and behaviors of the flora and fauna around them. For example, many tropical forest plants flower only for a few days when heavy rains follow a drought. They then produce fruit within weeks, providing food for a wide range of rainforest insects and animals. If climate change leads to a difference in the drought/rain sequence, the quantity of flowers and fruits may be reduced or, in the case of very wet weather, they may fail altogether. If this occurs, many species could starve, reducing the availability of food for yet more species.

Climate change can also create a mismatch between the time that food is available and the time when consumers are on hand to eat it. One example is this mismatch is the oak-caterpillar-great tit food web in Holland. Warmer temperatures led to earlier emergence of oak leaves, earlier birth of caterpillars, and earlier consumption of oak leaves by the caterpillars. But great tits, the birds that typically eat the caterpillars and manage their population, did not alter their usual time of nesting and reproduction. As a result, the great tits missed the opportunity to feast on caterpillars, and their population declined while the number of caterpillars increased.

Because phenological events are so sensitive to climate change, phenology has become a leading indicator that researchers can use to study and predict its impact. The more that researchers know about phenology, the more success they will have in understanding why an animal might feed on a new type of plant, forage in a new location, or develop different breeding habits. It also helps explain why a particular plant might produce seed or fruit at a different point in the phenological cycle.

The National Phenology Network, as well as government agencies like the National Oceanic and Atmospheric Administration, are working to gather long-term phenology records related to a huge range of plants and animals. These tools will make it easier for researchers to compare and contrast plant and animal responses to climate change over time and in different locations. Armed with this information, land managers will be better equipped to plan for the impact of climate change on plants, animals, recreation, forestry, and farming.

Watch the video: Phenology series episode 1: What is phenology?