Don’t get bit by phenology indicators

You know how those moisture-retaining gels swell when placed in water? That’s what I envision happens to brains of new gardeners as they soak up any and all available how-to gardening information – I was a novice gardener once long, long ago and did just that. It’s important to seek learned, sound advise from gardening friends, trusted nursery staff, local agriculture extension departments, books, blogs, websites, and magazines. Unfortunately not all gardening information is as clear as it should be.

white-lilac-4-5-09_edited Take the recent issue of Horticulture magazine. In the Q & A section and also online, the editors list characteristics of plants that purportedly indicate it’s time to do other gardening tasks. These ‘indicator’ plants – for example lilac shrubs, oak trees, daffodils, dogwood, lily-of-the-valley, and others – can serve as hints for sowing seeds or planting transplants. Many on the list make sense, such as planting cool season crops (peas and lettuce for example) when lilac leaves are about as big as the ears of a mouse or when daffodils bloom.

Such clues come from years of phenological observations. Scientists, gardeners, farmers, and general nature lovers have watched the timing of plants leaf-out, flower, seed ripening, late season leaf color changes, and leaf drop and noted correlations between the growth timing of indicator plants and the progress of the seasons – similar to that done among Project BudBurst scientists and citizen volunteers. Likewise observations can be made for animal habits. These observations provide valuable general information on overall climate change, plant and animal characteristics, and how weather pattern changes impact every living thing.

But general observations do not take local conditions into account … Horticulture neglects to point this out. Some of the correlations on their list make sense – such as using lilacs and daffodil stages as indicators for planting peas and lettuce (cool-season crops). But some of the suggestions could set up novice gardeners for failure. For instance, among the list of  “some common garden plants and what they indicate to you:” Horticulture mentions planting squash and cucumbers when lilac flowers fade, or beans when lilacs are in full bloom.

In my neck of the woods (Connecticut zone 6a) lilac flowers faded last week after blooming 2 to 3 weeks earlier than ‘normal’ which means outdoor soils are still too cool to allow warm-loving squash, cucumber, and bean seeds to thrive. Such seeds, when planted in cool soils, sit in a sort of suspended animation while waiting for soil temperatures to warm. The past week a couple of nights brought below freezing temperatures in most of Connecticut’s zone 6a, and cloudy, wet weather.  ( Connecticut has three cold-hardy zones, 6a , 6b, and 5a.) Soil just doesn’t warm very quickly when temperatures are this low and the sun doesn’t shine.

Lavender Touch Eggplant Two other indicator plant suggestions – to plant tomatoes when lily-of-the-valley blooms, and peppers and eggplant when bearded iris bloom – could entice novices to plant these warm-season crops in the ground too early as well. In my neck of the woods weekend air temperatures were warm, but the soils are still too chilly to encourage tomatoes, peppers, or eggplant to do more than hang dormant until the soil warms. Such exposures often stunt warm-season transplants to a point from which they may never recuperate. And while there are some maneuvers one can do to warm soils up earlier than would otherwise happen, the use of such techniques is not generally common.

I expressed my concern as follows :

Dear Horticulture Editors,

I applaud your Q & A piece (June/July 2010 issue) on phenology – I’ve participated in Project BudBurst for the last two years and highly recommend the project to others. However, some of the indicator plant suggestions you list could lead novice gardeners to failure. Spring blooms have been unusually early in my zone 6a garden this year. Were a novice gardener to plant tomatoes when lily-of-the-valley bloomed, they would have placed warm-loving transplants into the ground when actual nighttime temperatures fell to freezing. Likewise, bearded iris began blooming around May 15, yet soils remain way too chilly for warmth-loving peppers and eggplant.

Since outdoor planting dates can vary significantly according to locale, wouldn’t it have been responsible to advise gardeners to take note of local conditions and seek planting date advice from trusted local sources?

Nationally geared magazines often rely on generalities that suit gardens across the U.S. However, when it comes to spring or fall planting dates nothing beats solid local knowledge and experience. So take note …  when seeking temperature, rainfall, or hardiness questions about plants, do so locally.  It just might save your valuable tomato, pepper, and eggplant transplants from hypothermia, and you from a lot of extra and unnecessary planting and angst.

6 comments for “Don’t get bit by phenology indicators

  1. May 20, 2010 at 12:35 am

    Thanks for this info. I recently read a blurb about phenology. The subject is new to me, but looked worth reading up on. Perhaps the suggestions would be better used in combination with other indicators? For example, I’ve heard that tomatoes can be planted when night temperatures are above 50 degrees and the other heat lovers (peppers, beans, melons, etc.) when the night temps are above 55 degrees. This has been much more helpful than the general range of dates on seed packets or even trying to figure out when we are past the average last frost date. The temperatures vary so much from year to year and even within a short distance in the same zone. I garden in SE CT and have a gardener friend closer to the SW CT. When her daffodils were finishing, mine were just beginning. Heck, even along my street all the other daffodils were a week ahead of mine.

  2. joenesgarden
    May 20, 2010 at 7:16 am

    Phenology is, indeed, an interesting science, Kate. Check out Project BudBurst (link on my sidebar under Gardening Links) for more info. New gardeners should definitely seek advice from trusted local nursery staff – and I mean local, not staff at big box stores – on when it’s safe to plant tender annuals.

  3. May 20, 2010 at 8:09 am

    I kept an elaborate spreadsheet of bloom times and duration so I could design how my garden should look all together… then found that plants don’t adhere to the script. They didn’t follow the timing in the literature. I had an abelia that was supposed to bloom in May, and it didn’t leaf out until early June, then bloomed in August…..

  4. joenesgarden
    May 20, 2010 at 8:55 am

    Wait … your plants didn’t act as expected? I’m shocked … shocked I tell you. Gardening keeps us humble, doesn’t it Laurrie.

  5. May 20, 2010 at 10:46 pm

    I guess it’s as good as the Farmer’s Almanac, but more complicated!

  6. joenesgarden
    May 21, 2010 at 7:19 am

    It’s good to study phenology, Deb, to pick up trends. For local expertise, though, there’s nothing like local experts.

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