Documents: Special Interest: Garden Musings:

Phenology
by Dan Clost
by Dan Clost

email: dan.clost@sympatico.ca

First serious garden earned 25 cents from the Kemptville Horticultural Society when I was 12. Have been poor in horticulture ever since but rich in spirit.

Went to work writing the Good Earth column (over 500 articles published in newspaper, magazine, website and journal.) and learned that what was printed wasn't what I wanted to say and certainly not what Gentle Reader understood me to say. Subsequently have developed a certain clarity and economy of words.

Day job- nursery and production manager for a large nursery/garden centre
Side job- Garden restoration and renovations, design consultations, remedial pruning.
Night job- garden writer and communicator (overnight success in another 20 years)

Dan gardens in Canadian Zone 5b


September 8, 2002

I'd like to introduce a new term to you: plant phenology. As we go along there will be many of you who will say, "Well, isn't that just like a college boy. Invent a fancy term for something we've been doing for years." If you are one of those people, then I can almost guarantee that you grew up on the farm.

Over the years we have gained some ability to manipulate the growing of plants. We do this by genetics, chemical intervention (pesticides are only one example) and by analysing increasingly accurate weather and environmental data. We look at the date of last frost, we add up the degree-days (a measure of the heat that has accumulated over a specific base temperature) and measure the soil temperature. All this before planting. For the less scientific amongst us Ontarians, we wait until that other popular measuring instrument says that Victoria Day is here. Then we plant our gardens.

We do this because we know that there is a direct relationship between plant growth and temperature. However, if you examine closely, for example, the date of last frost, you will find words like accurate seven years out of ten. Sort of like those polls where the pundits interview three people and state their views are accurate ± 5%, 19 out of 20 times.

Finally we arrive at the phenology part. Plants are rather accurate measurers of degree-days. You won't see a lilac blooming in January. The buds on pussy willow don't swell in December. The idea behind this is to simply pay attention to nature's timing through the growth of plants.

One of our irritating pests, indoor and out, are scales. You know you have them on your house plants, such as a weeping fig or a lemon tree, when the leaves are covered with a sticky exudate and a black mouldy appearing fungus. Out of doors, they feast on pines and spruces amongst other plants. Horticultural oils are an excellent means of control (and they can be organic) but the timing of application is critical.

Remember our friend, Syringa vulgaris (lilac)? It seems that it blossoms at the same time those pesky critters hatch: not seven out of 10 times or even 19 out of 20 times (±5%) but every time. This is important because you have about a ten-day window before the little varmints develop their armoured shell. This is only one example.

Another relationship has been shown between red maple and the hatching of tent caterpillar larvae. As Dr. Dan Herms advises, when you see an insect active in your area make a note of what is in bloom at that time. Eventually you will have a realistically accurate timetable of biological events in your garden. You can use this to actively seek out pests in their earliest stages and take corrective measures. It is also equally effective when you are expecting beneficial insects to arrive.

There is absolutely no doubt in my mind that record keeping is one of the best gardening tools we have. Your notes can make for interesting winter reading as well.

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