Record Plant Leaf and Flower Stages and Interpret Monthly Observation Charts

The short answer

Plant stage records and monthly observation charts answer different questions, so keep them apart. To record leaf and flower stages, return to the same marked plants or patches at least weekly, check each stage against a written definition, and mark it Yes, No or Uncertain on every dated visit. A monthly observation chart counts how many records of a species fall in each month. It does not tell you when that plant leafed out or bloomed, and it does not tell you how abundant the plant is. Outside research helps your prairie records only when it measured the same kind of stage, in a comparable species, habitat and region, using a comparable method.

Two kinds of plant timing data

Phenology is the study of when recurring life-cycle events happen, such as new leaves appearing or flowers opening. A phenology record follows one plant through time and notes which stages are present on each visit. An occurrence chart pools records of a species from many observers and places and sorts them by month. Both are useful on the Montana prairie. They support different conclusions, though, and mixing them is the most common way to misread either one.

Reading a monthly occurrence chart: the Pomme-de-prairie example

The Montana Field Guide lists Pomme-de-prairie (Pediomelum esculentum), a member of the pea family, Fabaceae. Its habitat includes plains grasslands, which are often sandy, and pine woodlands, and Great Plains Sand Prairie is listed as an associated community. That makes it a relevant prairie plant to watch. The guide's observations-by-month chart for the species contains 880 records. Records that span more than one month are excluded.

Month	Records	Share of 880
January–March	0	0%
April	1	about 0.1%
May	35	about 4%
June	388	about 44%
July	291	about 33%
August	118	about 13%
September	46	about 5%
October	1	about 0.1%
November–December	0	0%

Read the chart literally. June and July together hold 679 records, about 77% of the total, and all but two records fall between May and September. That tells you the species was recorded most often in early summer. It does not show bloom dates, flowering stages or how many plants were present, because the chart contains none of those measurements.

Supported: the months in which records of the species were made, and their relative counts.
Supported: the months with no single-month records in this dataset.
Not supported: the date flowering starts or peaks.
Not supported: whether a plant had leaves, buds or open flowers when it was recorded.
Not supported: abundance, or a rise or fall in the plant population.

Defining leaf and flower stages before you record them

A stage record is only as reliable as its definition. The USA National Phenology Network (USA-NPN) publishes plant and animal phenophase definitions. A phenophase is an observable stage, such as open flowers. Version 2.1, dated March 2023, covers temperate and water-limited ecosystems. Its forb definitions apply to non-woody flowering plants like Pomme-de-prairie:

Initial growth: new growth after a period of inactivity. On each shoot, this stage ends when the shoot's first leaf has fully unfolded.
Leaves: at least one live, fully unfolded true leaf is present. Cotyledons (seed leaves) and dead leaves do not count.
Flowers or flower buds: fresh flowers or expanding buds are present. Dormant buds and wilted flowers do not count.
Open flowers: fresh flowers are present with reproductive parts visible inside the opened floral structures. Wilted flowers do not count.

These stages overlap. A Yes for Open flowers also means Flowers or flower buds is present, so a record marking open flowers but not flowers or buds contradicts itself. Apply the functional-group and species-specific wording exactly as written, and don't stretch a definition to cover something it excludes. A plant with only wilted flowers is No for Open flowers, for example. Definitions and intensity options can be revised, so keep the version that applies to your species on the date of each observation.

Preparing and carrying out repeat observations

Choose individual plants or a defined patch, and record the evidence for your identification, such as photographs of the leaves, flowers and overall form.
Give each plant or patch an ID and note its location and habitat type. A sandy grassland patch, for example, should be described as sandy grassland.
Ask the land manager before you enter a site, mark plants or collect anything, and follow their rules for access and marking.
On public prairie, use markers the manager approves, and record locations so you can find the plants again without searching through the vegetation each time.
Write down which definition version you are using and which phases you will check.
Visit the same plants or patch on every visit. Changing to different plants breaks the record.

How often to visit

Nature's Notebook, the USA-NPN observation program, asks observers to visit at least once a week and more often when plants are changing quickly. USA-NPN training material recommends checking forbs two or three times a week around the start and peak of flowering. More frequent visits narrow the gap between the last No and the first Yes, which is the window in which a stage actually began.

Recording each visit

Date every visit. For each phase you check, record Yes if it is present, No if it is absent, and Uncertain if you cannot decide. Leave the phase blank only if you did not check it. A No and a blank mean different things: a No is evidence that the stage was absent, and a blank is no evidence at all. This original worksheet layout keeps the necessary fields together:

Plant/patch ID | ID evidence | Location & habitat | Visit date | Definition version | Phase | Criterion used (and its source) | Yes/No/Uncertain/unchecked | Photo | Comments
---------------+-------------+--------------------+------------+--------------------+-------+--------------------------------+----------------------------+-------+---------
P1             |             |                    |            |                    |       |                                |                            |       |

Example: interpreting a first positive record

Here is a hypothetical record. Plant P1 is marked No for Open flowers on June 3 and Yes on June 7, with the same definition used on both visits. June 7 is the first recorded positive visit. Keep both dates. Don't assign an exact onset date somewhere between them, and don't attribute the timing to climate or any other cause. One plant over one season can't establish either.

Keeping chart totals separate from stage records

Keep monthly occurrence totals in their own table, apart from your stage worksheet. Don't add your visits to an occurrence count, and don't read a month's record total as the flowering season. If your stage records show open flowers in June, that is a finding about your marked plants. It doesn't confirm or explain June being the busiest month on the occurrence chart, because the chart never recorded stages.

Judging whether outside research applies to Montana prairie records

Published phenology studies, such as those on spring shifts, flowering change in subalpine communities, or long-term Northern Rockies records, are tempting benchmarks. Before you use one, compare it with your own record:

Species: is it the same species or a close relative?
Functional group: forb, grass, shrub or tree?
Region and habitat: does a subalpine meadow or a coastal site match plains grassland?
Measured stage: is it flowering onset, peak, open flowers, or something else?
Observation frequency: weekly, several times a week, or occasional?
Definition version: were the stages defined the same way?

A study that measured flowering onset can't stand in for a chart that counts monthly occurrences, and a general flowering table can't stand in for local stage records. The USA-NPN training slides illustrate this. Their flowering-time table comes from a Gulf Coast phenology trail context, so it is not a Montana bloom calendar. Likewise, the USA-NPN publications list includes monitoring methods, protocol updates, and Caprio's work on lilac bloom in Montana. Those citations are leads to read, not results you can transfer. If you can't settle whether a study is comparable, treat it as a question for your own observations, and don't apply its dates or causal conclusions to your prairie plants.