Unit II · Lesson 15SEASONAL GROWING CYCLES

Professor's Introduction

Sealed with the mark of Professor Beryl Fernfoot, Master Herbalist of the Herbology Greenhouse, Head of House Oriens.

Take your time settling in, scholars,

We have spent this unit learning about soil and sunlight and water, the things a plant needs. But there is another dimension to a plant's life that we have not yet named, and it is the one you are already living inside: time.

A garden is never the same garden twice. The bed you planted in April is a different place in July, and a different place again in November. The plants know this. They keep their own calendars, written in light and temperature, and they follow them with a patience that puts our own schedules to shame.

Today we learn to read those calendars. We will learn how long a plant lives, how it sleeps through winter, and how to plan a whole year of growing. Bring your journal. We are going to draw the year itself.

— Professor Beryl Fernfoot, Herbology Greenhouse • Master Herbalist • Head of House Oriens

The line beneath the map is our road: every stop a place where the knowledge of plants changed, every lesson a step along it.

The Three Lifespans

A zinnia in flower, with a bumblebee at work. Zinnias are annuals: germinate, grow, flower, set seed, and die, all in one growing season — and because they cannot survive frost, they wait until all danger of it has passed. The bee is one of the season's own signals: the first bee on the first flower tells you the year has turned.

Photograph by Wilfredor, Jardin botanique Roger-Van den Hende, Quebec City, October 2023. CC0.

Parsley (Petroselinum crispum) in its second year — the year this plate draws. A biennial spends its first year as leaves and roots only, storing food; in the second year it flowers, sets seed, and dies. Do not mistake the quiet, leafy first year for a plant that has failed to flower.

From Köhler's Medizinal-Pflanzen (Franz Eugen Köhler, 1897). Public domain.

Daylilies (Hemerocallis fulva and H. flava) — herbaceous perennials. They flower through summer, die back to the ground each autumn, and return from the living roots each spring, year after year: the backbone of a lasting garden asks for a permanent home and rewards patience.

Otto Wilhelm Thomé, Flora von Deutschland, Österreich und der Schweiz (1885), plate 131. Public domain.

Every plant is born with a schedule. Some live fast and die young, pouring everything into a single season of flowers and seeds. Some take two years to complete their work. And some settle in for the long term, returning year after year like old friends.

Botanists describe these schedules with three words: annual, biennial, and perennial.

★ Annuals complete their entire life cycle in a single growing season. They germinate from seed, grow, flower, set seed, and die, all within one year. Marigolds, petunias, zinnias, and basil are familiar annuals. Many of the bright bedding plants sold each spring are annuals. Their strategy is simple and bold: make as many seeds as possible before the season ends, and trust the next generation to carry on.

There are refinements within the annual family. Hardy annuals tolerate light frost and can be sown outdoors in early spring, or even in autumn. Sweet peas and calendula belong here. Half-hardy annuals cannot survive frost and must wait until all danger of frost has passed; marigolds and zinnias are the classic examples. And winter annuals reverse the usual pattern: they germinate in autumn, overwinter as small rosettes of leaves, and flower in late winter or early spring. Chickweed is a common one, though gardeners rarely celebrate it.

★ Biennials need two growing seasons to complete their life cycle. In the first year, they grow only leaves and roots, building up food reserves and establishing themselves. A foxglove in its first year is just a low rosette of leaves, easy to overlook. In the second year, the plant flowers, sets seed, and dies. Parsley, carrots, and foxglove are biennials. Some plants grown as biennials, like sweet william, are botanically short-lived perennials, but gardeners treat them as biennials because they perform best in their second year and grow untidy afterward.

Check in: A plant spends its whole first year as a low rosette of leaves and flowers only in its second year. Which of the three lifespans is it living — and what must its gardener not mistake that quiet first year for?

★ Perennials live for more than two years, returning season after season. They are the backbone of a lasting garden. There are two great kinds. Herbaceous perennials die back to the ground each autumn; their roots survive underground through winter and send up new shoots in spring. Hostas, daylilies, and mint are herbaceous perennials. Woody perennials keep living stems above ground through winter: trees, shrubs, and woody vines like lilac and rosemary in mild climates.

★ Some perennials are tender, meaning they cannot survive frost. A geranium is a perennial in a warm climate and an annual in practice where winters are cold, because the cold kills it. Gardeners in cold regions either grow tender perennials as annuals, replacing them each spring, or bring them indoors for winter. This is why the same plant can be called an annual in one garden and a perennial in another. The label describes how the plant behaves in your climate, not only what it is in itself.

Why does any of this matter? Because it changes everything about how you care for a plant. An annual asks for one good season and then bows out; you plan to replant. A biennial asks for patience through a quiet first year; you must not mistake its leafy rosette for a failure to flower. A perennial asks for a permanent home and rewards you with increasing abundance; you plan around its return. When you know your Scholar's Familiar's life cycle, you know what to expect from it, and you stop worrying when it does exactly what its kind was always going to do.

Sealed with the mark of Professor Beryl Fernfoot, Master Herbalist of the Herbology Greenhouse, Head of House Oriens.

You are doing well. I know these three words sound like vocabulary to memorize, but they are really three different ways of being alive, and once you have seen them in real plants, you will never forget them.

Look at your Scholar's Familiar with new eyes now. Is it racing through one season, or settling in for years? The answer changes how you will care for it, and that is worth knowing.

— Professor Beryl Fernfoot, Herbology Greenhouse • Master Herbalist • Head of House Oriens

❦ In your workbook: record the three lifespans in your own way — annual, biennial, and perennial, with an example of each and what each one asks of its gardener — copy, sketch, or note what matters.

Dormancy: The Long Sleep

A woodland asleep, not dead. The deciduous trees have sealed off and dropped their leaves and wait with their energy in their roots; the evergreen keeps its leaves and replaces them gradually. In February, a plant that looks like this is almost certainly dormant: scratch a twig — green and moist beneath the bark means alive. Do not dig it up in a panic. Wait.

Photograph by Juliancolton, Black Creek Preserve, Hudson River valley, New York, February 2012. CC0.

In autumn, something remarkable happens in the garden. Growth slows. Leaves change color and fall. The whole green world seems to shut down. It looks like death, and every new gardener fears it is. It is not death. It is dormancy, and it is one of the cleverest things plants do.

★ Dormancy is a period of suspended growth, a kind of deep rest that plants enter when conditions turn unfavorable. For most temperate plants, the trigger is the combination of shortening days and falling temperatures. The plant senses winter coming and prepares: it moves energy down into its roots, seals off vulnerable tissues, and waits. Above ground, herbaceous perennials let their stems die back entirely. Deciduous trees and shrubs drop their leaves, sealing the scars where the leaves were attached. Below ground, bulbs, tubers, and root systems sit quietly in the soil, alive but inactive.

★ This rest is not optional. Many plants require a cold period to grow properly afterward. This is called vernalization: the process by which prolonged cold enables a plant to flower. Winter wheat must experience weeks of cold before it will produce grain. Many bulbs will not bloom without a proper chill. The cold is not the enemy of these plants. It is part of their instruction manual.

★ How do you tell a dormant plant from a dead one? This is one of the most useful skills a gardener can learn, and it takes patience. First, check the roots and crown: scratch a small spot on a stem or twig with your thumbnail. If the tissue beneath the bark is green and moist, the plant is alive. If it is brown and dry all the way through, that stem is dead. Second, be patient: many plants break dormancy late. A fig tree can look entirely lifeless until June and then leaf out as if nothing happened. Third, remember the calendar: if it is February and your perennial looks dead, it is almost certainly dormant. Do not dig it up in a panic. Wait.

Check in: It is February and your perennial looks entirely dead. What does this lesson tell you to do — and what does the scratch test tell you if the tissue beneath the bark is green and moist?

Dormant plants still need you, though less often. Check them occasionally. Soil in pots can dry out completely over winter, even in the cold, and a desiccated root system may not recover. Water sparingly when the soil is dry, and keep pots where they will not freeze solid repeatedly. A dormant plant is resting, not abandoned.

There is a quiet beauty in dormancy that I hope you will come to appreciate. The garden in winter is not empty. It is full of sleeping things, each one holding its plans for spring in the dark. Learning to trust that sleep, and not to disturb it, is one of the deeper lessons of this craft.

❦ In your workbook: record dormancy in your own way — what triggers it, what vernalization is, and how to tell a sleeping plant from a dead one — copy, sketch, or note what matters.

Reading the Four Seasons

Prolonging the garden through the winter months indoors, as a 1912 house-plant manual pictured it. Winter is the season of tending what continues: houseplants, tender perennials carried inside out of the frost, and stored bulbs checked now and then for rot — while the gardener plans, and next year's garden is designed.

From Gardening Indoors and Under Glass (1912), via Internet Archive Book Images. No known copyright restrictions.

Once you understand life cycles and dormancy, you can read the whole year as a gardener does. Each season has its own work, its own signs, and its own pleasures.

★ Spring is the season of waking. Day length increases, soil warms, and dormant plants break their rest. This is the season of sowing: start seeds indoors or direct-sow hardy plants outdoors after the soil can be worked. It is the season of transplanting seedlings, dividing crowded perennials, and feeding hungry soil with compost. Watch for the signs your own garden gives you. The return of certain weeds, the leafing of particular trees, the first bee on the first flower: these are the local signals that the season has truly turned. Your Scholar's Familiar will show you its own spring awakening. Record the date. It will not be the same every year, and that variation is itself worth studying.

Summer is the season of growth and abundance. Plants put on size, flower, and set fruit. This is the season of watering, weeding, and harvesting. It is also the season of vigilance: heat stress, pests, and diseases all peak in summer. Mulch to keep roots cool and moisture in the soil. Harvest herbs in the morning, when their volatile oils are at their strongest, a lesson we will explore fully in Unit IV. Deadhead spent flowers to encourage more blooms. And take time to simply observe. Summer is when your plant shows you what it is capable of, and your journal should be fullest now.

★ Autumn is the season of gathering and preparing. Harvest the last crops, collect seeds for next year, and take cuttings of tender plants you want to carry through winter indoors. This is the season to plant spring-flowering bulbs, to divide perennials, and to feed the soil with fallen leaves and compost. As days shorten, watch your garden begin its slow shutdown: the color changes, the leaf fall, the retreat. Help your plants prepare by easing off on fertilizer, which encourages tender new growth that winter will damage, and by watering deeply once before the ground freezes, so roots go into dormancy hydrated.

Check in: Why does the gardener ease off on fertilizer in autumn — what would the fertilizer encourage, and what would winter do to it?

Winter is the season of rest and planning. The garden sleeps, and the gardener plans. This is the season for studying seed catalogs, sketching next year's beds, repairing tools, and reading. It is also the season for tending what continues: houseplants, overwintering tender perennials indoors, and any cold-hardy crops under cover. Check stored bulbs and tubers for rot. And check your dormant outdoor pots now and then, because winter wind can dry soil even in the cold. Winter is not empty time. It is the season when next year's garden is designed.

★ Notice how the work of each season prepares the next. Spring sowing depends on winter planning. Summer harvest depends on spring planting. Autumn preparation determines how well things survive winter, and winter rest makes spring growth possible. The year is a circle, not a line. Once you have walked it with a plant of your own, you will feel that circle turning, and you will never quite see a garden the same way again.

❦ In your workbook: record the four seasons in your own way — each season's work, its signs, and how it prepares the next — copy, sketch, or note what matters.

Your Climate, Your Calendar

The 2023 USDA Plant Hardiness Zone Map. Thirteen zones, each spanning 10°F of average annual minimum winter temperature, with "a" and "b" half-zones of 5°. When a plant tag says "hardy to Zone 5," this map is what it means. Zones measure cold tolerance only — they say nothing about summer heat, rainfall, or soil — and your frost dates, not the map, bound your growing season.

USDA Agricultural Research Service and the PRISM Climate Group, Oregon State University, 2023. Public domain (U.S. federal work).

Everything in this lesson so far has been general. Now let us make it personal, because your garden lives in a particular place with a particular climate, and the calendar that matters is yours.

★ Gardeners in the United States use two essential tools for this. The first is the USDA Plant Hardiness Zone Map, published by the United States Department of Agriculture. It divides the country into 13 zones based on the average annual minimum winter temperature, each zone spanning 10 degrees Fahrenheit, with subzones "a" and "b" marking 5-degree steps. Zone 1 covers the coldest parts of Alaska, where winter lows can reach minus 60. Zone 13 covers the warmest parts of Hawaii and Puerto Rico, where winter lows stay above 60. When a plant tag says "hardy to Zone 5," it means the plant can survive the coldest winters typical of Zone 5 and warmer. Find your zone before you buy a perennial. It is the single most useful number in American gardening.

The hardiness map was most recently updated in 2023, and about half the country shifted into a warmer half-zone compared to the previous map. Zones describe cold tolerance only. They say nothing about summer heat, rainfall, humidity, or soil, all of which matter enormously. A plant hardy in your zone can still fail in your garden if the summers are wrong for it. Treat the zone as a starting point, not a promise.

★ The second tool is your area's frost dates: the average date of the last spring frost and the first autumn frost. The growing season, the stretch of frost-free days between them, is the window in which tender plants can live outdoors. A gardener in Lawrence, Kansas plants tomatoes after the last spring frost, usually in late April, and expects the first killing frost around mid-October. A gardener in Minneapolis works with a far shorter window. These dates are averages, not guarantees; frost can come early or late in any given year. Experienced gardeners watch the forecast, not just the calendar, and keep row cover or old sheets ready for surprise cold snaps.

Check in: Your hardiness zone says a perennial can survive your winters. What does the zone not tell you — and why are your frost dates still only averages, not promises?

★ Together, your zone and your frost dates define what is possible in your garden. They tell you which perennials will survive your winters and when your growing season begins and ends. Write them in your journal. They are the coordinates of your gardening life.

One more consideration, especially for students growing indoors: your windowsill has its own microclimate, which we studied in Lesson 14. Indoor plants follow a gentler version of the seasonal cycle, responding to the changing light through your window even when the temperature stays steady. Your Scholar's Familiar may slow its growth in winter and surge in spring without ever experiencing frost. That is its own honest cycle, and it is worth charting just as carefully.

❦ In your workbook: record your climate and your calendar in your own way — what the hardiness zones measure, what frost dates bound, and what neither one can promise — copy, sketch, or note what matters.

The Year of Your Familiar

We end this lesson where we began the unit: with your Scholar's Familiar.

You have tracked this plant through soil and sunlight and water. Now I am asking you to do something larger: to imagine, and then to observe, its entire year. What does it do in spring? When does it grow fastest? Does it flower, and when? When does it slow down? Does it go dormant, and if so, what does that look like? What will it need from you in each season?

If you have no living plant of your own, adopt one you can visit regularly: a park tree, a neighbor's garden bed, a sidewalk weed, a store display. Visit it in every season and chart its year the same way. The observation is the lesson, not the ownership.

You will not be able to answer all of this today. That is the point. This is a long observation, the longest you have undertaken so far. Begin the chart now, with what you know and what you can reasonably predict from your plant's life cycle. Then keep it across the seasons, adding what you actually see. By this time next year, you will hold a complete annual cycle of a living thing, recorded by your own hand. There are few documents in a naturalist's life more satisfying than that.

The greenhouse doors stand open in every season. The work changes, but it never stops, and neither does the wonder.

❦ In your workbook: record the year of your Familiar in your own way — what it does in each season, when it rests, and what it will need from you — copy, sketch, or note what matters.

Guided Observation: Reading the Season You Are In

This lesson's observation asks you to read the season that is actually outside your window today — whatever season that is — the way this lesson teaches. No season is the wrong season to begin: the year is a circle, and you may step onto it anywhere.

You will need:

• your Scholar's Familiar, or a plant you can visit regularly — a park tree, a neighbor's garden bed, a sidewalk weed, a store display
• your journal and a pen or pencil

Read the plant in front of you. Look at your plant as it stands today and answer from what you can see: Is it growing, flowering, fruiting, dormant, or resting? Are its leaves fresh, mature, coloring, or fallen? Does it show dieback, senescence, or new growth? Record the date beside what you see. It will not be the same every year, and that variation is itself worth studying.

Test before you judge. If your plant looks lifeless, do not decide from looks alone. Scratch a small spot on a stem or twig with your thumbnail. If the tissue beneath the bark is green and moist, the plant is alive. If it is February and your perennial looks dead, it is almost certainly dormant. Do not dig it up in a panic. Wait.

Plan the other three seasons from records. For each season you are not standing in, write what this lesson says your plant will most likely do then, from its life cycle — annual, biennial, or perennial; herbaceous or woody; tender or hardy — and mark those entries as predictions. Leave dated space beside each one to add what you actually observe when that season arrives.

Consider:

• What season are you standing in, and what is your plant doing in it today?
• Is your plant's present state growth, rest, or dormancy — and what evidence tells you so?
• Which of the lesson's local signals can you see from where you stand: the return of certain weeds, the leafing of particular trees, the first bee on the first flower?
• What have you predicted for the season farthest from today, and what will you watch for to test that prediction?

No plant of your own? Adopt one you can visit regularly and read its season the same way. The observation is the lesson, not the ownership.

Materials

Required (Level One — household items)

• Scholar's Familiar Journal and a pen or pencil.
• A large sheet of paper for the annual cycle chart.
• Internet access for looking up your hardiness zone and frost dates.

Suggested (Level Two — going further)

• Colored pencils or fine markers for the illustrated annual cycle chart.
• A local cooperative extension publication on frost dates for your county.
• A ruler and compass for drawing a neat circular year chart.

No assignment in this lesson requires a plant in a particular season, an outdoor bed, or a purchased specialty item: the chart and the coordinates can both be begun today, in any season, from the lesson, your records, and your sources, and completed by observation as the year turns.

Reflection Questions

Answer the following questions in your workbook.

1. Why might a gardener choose perennials over annuals for a permanent bed, and when might annuals be the better choice?
2. A friend panics in March because her lavender looks brown and lifeless. Using what you learned about dormancy, what would you tell her, and what would you check before deciding anything?
3. How does knowing your frost dates change the way you plan a garden, compared to planting whenever it feels like spring?
4. In what ways is your Scholar's Familiar's annual cycle similar to and different from your own yearly rhythms of activity and rest?

Workbook Checklist — Lesson 15

In my workbook I have:

• ☐ distinguished annual, biennial, and perennial life cycles, and given an example of each
• ☐ explained what dormancy is, why plants enter it, and how to tell a dormant plant from a dead one — scratch test, patience, and the calendar
• ☐ described what happens in a garden across spring, summer, autumn, and winter, and how each season's work prepares the next
• ☐ looked up my USDA hardiness zone and my area's first and last frost dates, and said what they mean for planting
• ☐ begun my Scholar's Familiar's annual cycle chart across all four seasons — the current season from observation, the rest from records and prediction, with room to add what I actually see

☐ Lesson completed Date: ___ Signature: ___

Professor's Closing Note

Sealed with the mark of Professor Beryl Fernfoot, Master Herbalist of the Herbology Greenhouse, Head of House Oriens.

Dear scholars, you have finished Unit II. You began this unit by holding a handful of soil, and you end it by holding a whole year. That is no small journey.

Before you move on, take a walk outside, whatever the season. Look at what is growing, what is sleeping, and what is waiting. You know their schedules now. You are, whether you realize it or not, thinking like a gardener.

— Professor Beryl Fernfoot, Herbology Greenhouse • Master Herbalist • Head of House Oriens

Cross-Class Connections

Celestial Studies · Unit I, Lesson 3 — The Tilted Year: Why We Have Seasons

Your plants keep their calendars in light and temperature, Fernfoot's scholars — come up to the Tower and learn who writes those calendars. In my lesson the tilted Earth does the writing: solstices where the sun stands still, equinoxes where night comes out even, and January, nearest the sun and coldest in the north, to prove it was never distance at all. Read your garden's year here, then come and see it turn. — Professor Vesper Glimmerwick, Celestial Studies

Creative Arts · Unit V, Lesson 22 — Garden Structures: Supports, Cold Frames & Garden Models

Fernfoot has taught you when a plant wants shelter; my bench teaches you to build it. The cold frame in this lesson — sloping glazed lid, notched prop for venting, sited to meet the sun and refuse the frost — is overwintering built in wood and glass: the same craft the Paris market gardeners used to hold autumn back and bring spring forward. Build it small and true here, and your Greenhouse seasons will run longer for it. — Professor Cogbranch Timberclank, Creative Arts Workshop

Further Reading & Sources

• Understanding USDA Plant Hardiness Zones — A clear walkthrough of the 13-zone system, what the a/b subdivisions mean, and how gardeners use the map.
• What are USDA Plant Hardiness Zones? — Zone definitions, temperature ranges, and the honest caveat that zones measure cold tolerance only.
• Hardiness zone — Wikipedia's overview of the USDA system, its history, and alternative systems used in other countries.
• Definitions of Annual, Biennial, Perennial, and Ephemeral — Edinburgh Garden School's precise definitions, including hardy and half-hardy annuals and tender perennials.
• Annual, Biennial, and Perennial Plants: What's the Difference? — An accessible comparison with examples of each life cycle.
• Classify Plants by Life Cycle/01%3A_Plant_Identification/1.10%3A_Classify_Plants_by_Life_Cycle) — A botany textbook chapter on life cycle classification, including winter annuals and hardy annual types.

Browse the Herbology shelf in the school Library for readable editions of these works.

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