Phenology - Use Science to Plan Your Garden!

Phenology - Use Science to Plan Your Garden!

Phenology header

Spring is sooner recognized by plants than by men. -Chinese proverb

Nature’s calendar tells plants when to flower or go to seed. But since seeds are deep underground inside their hard shells, how do they know when it's safe? Even meteorologists struggle with accurate prediction, even with satellites and radar, so how does nature know when it's time? 

Nature's ebb and flow, temperatures, sun, the tug of the moon, plus the changing seasons, give plants all the information they need to stay right on schedule!


vineyard pictureThe word Phenology is defined as the study of cyclic and seasonal natural phenomena in relation to climate and plant and animal life. Derived from Greek “phaino,” meaning to appear, and “logo” which is to study. Phenological records of Japan’s Cherry blossom bloom time, vineyard weather logs and more have been used for centuries!

Temperatures and daylight length trigger hormones and temperature-sensitive chemicals that regulate plant and insect basic functions. Gardeners can then use these clues in their own garden to know when planting time may be right, when certain pests might be active and when to break out their allergy medicine!

Old Wives Tales

Plant peas on St. Patrick's Day pictureThere are many old proverbs, folklore and superstition, that may contain a grain of truth:

  • Plant Rosemary to repel evil spirits
  • “If Oak before Ash, prepare for a splash - If Ash before Oak, you’re in for a soak!”
  • When leaves turn their backs to the wind - expect rain
  • Plant Peas on St. Patty’s Day
  • Wooly Bear Caterpillar bands indicating the length of winter
  • Plant Potatoes on Good Friday
  • Ripe Persimmon seeds foretell winter’s severity:
    • If Fork shaped - mild winter
    • Spoon-shaped - you’ll be scooping snow
    • If Knife shaped - Temperatures will cut like a knife
  • Temperature based on Cricket chirps per minute

Phenology in the Garden

Nature provides many hints for when those lawn and garden chores can be done, even when the weather is unpredictable! 

In the landscape

  • Maple leaves and perennials Maple leaves emerging - Plant perennials
  • Grasshopper eggs hatch when old fashioned Lilacs flower
  • Canada Thistles bloom when Apple Maggot Moths emerge
  • Oakleaf Hydrangeas blooming - Treat fall webworms
  • Redbuds blooms - Watch for Gypsy Moth caterpillars
  • Morning Glory growing or Elderberry flowering - Watch for Japanese Beetles
  • Treat Bronze Birch Borer when Arrowwood Viburnum & Weigela are in full bloom or Horse Chestnut flowers are finished 
  • Treat for Birch Leaf Miners when Mugo Pine candles form
  • Kousa Dogwood in full bloom - Spray for Bagworm because they’re hatching and susceptible!
  • Butterflyweed blooms - Time to treat for Scale, Lacebug & Japanese Beetle larvae
  • Spray Crabgrass seedlings when Mockorange blooms
  • When Crabapple flower buds form, then treat Tent Caterpillar

Saucer Magnolias are a great indicator species! New buds indicate it’s time to treat Tent Caterpillars. When they’re in full bloom, Spruce Spider Mites & Zimmerman’s Pine Moth larvae are emerging and it's the best time to spray them. When the petals drop, spray for Pine Sawflies.

Prune Roses, fertilize most lawns or apply Crabgrass pre-emergent when Forsythia flowers and Crocus bulbs bloom.

In the Vegetable Garden

vegetable garden phenology infographicYou know spring planting season has arrived when Blackberries bloom. Apple blossoms are a great indicator to plant bush beans, and plant climbing beans and cucumbers when the flowers fall. 

Lilac leaves emerging means it’s time to plant cool-season crops, lettuce and peas, while flowering Lilac hints it's safe to plant warm weather squash, carrots, cruciferous veggies, spinach and more. 

When Iris, Dogwood trees and Daylily bloom, it’s time to transplant hot weather veggies, tomatoes, corn, squash, eggplants and peppers. 

  • Plant corn when Oak leaves are the size of a squirrel's/mouse’s ear
  • When Crocus bloom - Ground temps are safe for radish, parsnip & spinach seeds
  • Watch for Asparagus spears when Pears bloom
  • When Redwing Blackbirds arrive or Forsythia blooms - Plant peas, lettuce & onion sets
  • Watch for Daffodils before planting root veggies
  • Quince in full bloom - It’s safe to transplant your cruciferous veggies outside
  • Peony blossoms - Time to plant heat-loving melons
  • Watch for Squash Vine Borers when Chicory flowers
  • Plant beets, lettuce, carrots, tender greens & potatoes when Dandelion’s bloom

Morel Mushroom hunters should watch for Dogwood tree flowers to drop, or when Redbuds begin to bloom to know when to start hunting!

Timing is Everything

timing picture with temperature All of the above is of course anecdotal and subject to microclimates, climate change, fancy new garden cultivars and hybridized plants, plus a wide range of other variables. It’s best to know your plants, know your garden, local weather and your local responses to climate. So careful observation of your area helps keep you on top of your landscape!

Soil temperatures, day length, and other cues cause temperature-related hormones in plants to ‘turn on’ at certain times, usually the right time! So it’s not a stretch to the imagination to realize plants and animals are very well in sync with their environment!

Get Connected

Can’t accept summer is over? Is it winter already? Where did spring go? 

Our busy lives have us so disconnected from the seasonal cycles that we’re always playing catching up, and that can be exhausting!

Keeping a garden journal tracking what you see and did each year helps you feel more in tune with the seasons, just the way your plants and wildlife are! So start your own and record backyard events each growing season! 

Suggestions to record in a Phenology/Garden Journal:

  • sample garden journalUnusual weather
  • Diagram of what you planted & where (vegetable gardeners - we’re looking at you)
  • Organize plant care tags
  • First & last frost dates
  • Melting of ice & snow
  • Events such as flowering times
  • Leaves emerging
  • Rainfall dates & totals
  • Birds & insects you see & when
  • Harvest dates & quality/quantity
  • Count Honeybees!
  • Photos, sketches, pressed leaves/flowers & garden mementos
  • Thoughts, dreams, future plans & ideas!

It’s also a fantastic way to get outdoors and commune with the natural world. Buy or make your own gardening journal, or download your favorite Smart Plant Home app (available for Android and Apple), then start recording! You’ll feel connected and informed!

Nature’s Calendar

Long before we had those fancy gizmos or even thermometers, farmers knew when to plant crops by watching indicator plants and animals because of how synchronized they are to nature’s life cycles. 

Nature Hills loves helping gardeners beautify their world and connecting people to the outdoors!

Get Involved

Want to become a citizen scientist and join others documenting and observing Phenology? Check out USA National Phenology Network and The Lilac Network to join others collecting phenological data to predict drought, assess wildfire risks and track climactic conditions and climate change impacts around the United States!

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