Calendar Alternatives to Timing Garden Planting

Gardening Sweet Spots
By Donna Hessel

We used to be able to depend on a calendar date to know when to expect the last frost or the “April showers that bring May flowers.” However, with climate changing every year, the standard dates are no longer reliable. Time to revert to the tried-and-true method of seasonal cycles in plants — phenology — to be sure that what you plant will grow and prosper. 

There are indications that the earliest hunter/gatherers kept track of seasonal changes, and when agriculture became common, more detailed records were kept. The Chinese had written records starting back nearly 1,000 years B.C. Robert Marsham, an English naturalist who lived in the 1700s, is considered  the father of phenology. However, it wasn’t until 1849 that the term ‘phenology’ was created to label the science of seasonal cycles in animals and plants.

Today, phenology is being used as an indicator of climate change. Plants and animals respond to long-term changes in the weather. Global warming has led to earlier springs. Many types of plants are breaking dormancy sooner and their life cycles are accelerated. Later falls have significantly lengthened the growing season. Maybe you’ve noticed these changes, too.  It’s not your imagination; it’s actually happening.

In addition to planting, phenology has other applications for the garden. Problems with insects tend to occur during certain life stages of a plant. And insects themselves have life stages that follow a schedule. Phenology can help determine when defensive measures should be taken. The same is true for various plant diseases. Indicator plants are often used to look for a particular pest and manage it in its vulnerable stages. Indicator plants are also used to time the planting of vegetables, applying fertilizer and pruning.

Controlling Pests According to Growing Degree Days
There are calculations available that farmers use to determine when to plant specific seeds, when to treat for invasive pests or weeds, etc. that are determined by “Growing Degree Days” (GDD). GDDs are based on threshold temperatures. Growing Degree Days are a measurement of the growth and development of plants and insects during the growing season. Development does not occur at this time unless the temperature is above a minimum threshold value (base temperature). The base temperature varies for different organisms. It is determined through research and experimentation. The actual temperature experienced by an organism is influenced by several factors. These factors affect growth and development. Due to these factors and some other scientific considerations, a base temperature of 50 degrees Fahrenheit is considered acceptable for all plants and insects.

Here’s an example you might find useful if Japanese Beetles attack your zinnias or other flowers and shrubs. Japanese Beetles emerge in Ohio at 921 GDD. Time to put out traps. The first adults emerge at 971 GDD. The first beetles to emerge are called “scouts.” They find the juiciest flowers and signal “this is where to eat” to later emerging beetles. If you know the GDD date and check the top of plants, the adult beetles can be knocked into jars of soapy water or alcohol and your beautiful flowers will be saved from later-emerging beetles. Don’t crush the beetles you find because crushing them releases pheromones – the same scent used in the traps to attract beetles. If you would like to explore this concept further, check the following websites: 

• ohiograpeweb.cfaes.ohio-state.edu/weather/gdd-your-area
• Ohio GDD Calculator: oardc.ohio-state.edu/gdd/

Timing Sowing According to Indicator Plants
Certain plants give a cue by blooming or leafing out that it’s time for certain activities such as sowing particular crops. Often the common denominator is temperature. Lilac, a spring-blooming shrub, is often cited as an indicator plant. When lilac leaves are the size of a mouse’s ear, it’s time to sow peas, lettuce and other cool-weather crops. When lilacs are in full bloom, it’s bean planting time. Time to plant squash and cucumbers once lilac flowers have faded.

Here are some other indicator plants and the cues they provide for vegetable gardeners:

• When daffodils begin to bloom, sow peas.
• When oak leaves are the size of a squirrel’s ear, sow corn.
• When apple trees shed their petals, sow corn.
• When dogwood reaches peak bloom, plant tomatoes and early corn.
• When lily-of-the-valley blooms, plant tomatoes.
• When daylilies begin to bloom, plant tomatoes and peppers.
• When bearded iris are in bloom, plant peppers and eggplants.
• When dandelions bloom, plant spinach, beets and carrots.
• When shadebush blooms, plant potatoes.
• When catalpas and mock orange bloom, sow cabbage and broccoli for fall harvest.

If perennials and annuals are your main “crops,” use these indicators:

• Plant perennials when maple leaves begin to unfold.
• When maple leaves reach full size, sow morning glories.
• Once aspen has leafed out, plant pansies and snapdragons.
• When crocus bloom, prune roses.
• When forsythia is blooming, crabgrass is germinating. Treat for it. Also prune roses and feed your lawn.
• When crabapple and wild plum are breaking bud, eastern tent caterpillars are hatching. Begin looking for and controlling them.

Planting by the Moon’s Phases
Gardening by the Moon is a growing trend, but the technique isn’t anything new. Gardeners and farmers have been using moon phase gardening for ages. Best of all, it’s a fairly simple process.

The basic idea behind Gardening by the Moon is that the cycles of the moon affect plant growth. Just as the moon’s gravitational pull causes tides to rise and fall, it also affects moisture in the soil. Therefore, it’s said that seeds will absorb more water during the full moon and the new moon, when more moisture is pulled to the soil surface. This causes seeds to swell, resulting in greater germination and better-established plants. 

Moon phase gardening takes into account two periods of the lunar cycle: the time between the new moon and the full moon (the waxing of the moon), and the time between the full moon and the new moon (the waning of the moon). Accordingly, annual flowers, fruit and vegetables that bear crops above ground should be planted during the waxing of the moon. Examples are corn, tomatoes, watermelon and zucchini.  Flowering bulbs, perennial flowers and vegetables that bear crops below ground should be planted during the waning of the moon. Examples would be onions, carrots and potatoes. As the moonlight decreases night by night, plants are encouraged to grow roots, tubers and bulbs.

The moon also impacts plant growth through geotropism, which is how plants grow in response to gravity. Roots grow downward in the direction of gravitational pull and stems grow upwards. You may have planted tulip bulbs incorrectly with the pointed end down and they have turned around and sent shoots upward.

While some gardeners rely solely on these methods, others consider them myths. But it certainly helps to consider them when you time the planting of your garden this year. If you believe the standard calendar dates are still working, remember that the last frost date for our area is May 15. Waiting to plant more tender annuals until Memorial Day is advisable.

 

Article sources:  Horticulture Magazine online newsletter 12-15-21; article by Ed Brotak. Gardening by the Moon: https://www.almanac.com/content/planting-by-the-moon. Photos courtesy pexels.com.