Bay Weekly

Beat the Heat — and the Weeds

By Dr. Francis Gouin

Gardening in the heat of the day is unhealthy. It’s one of those stresses those of us with gray or white hair in particular are told repeatedly to avoid during these hot muggy days when orange alert air pollution levels are anticipated.
    But did you know that gardening in the heat of the day also promotes the germination of weed seeds and the growth of weeds?

This Week
in the Garden

  Sheer your azaleas to control height. You have until August 1 to prune if you want an abundance of flowers next spring. Flower bud initiation generally begins around the third or fourth week in August with buds formed only on the terminal end of the new growth. This means that if you sheer azaleas after August 1, you are likely to enjoy fewer flowers next spring.

  Get tough on bagworms. Bagworms are already too big to control with organic pesticides such as Thurocide or Dipel. Once the bags are one inch long, you can control them only with a hard pesticide such as Sevin.

Ask Dr. Gouin your questions at [email protected].
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    Research conducted many years ago at the Boyce Thompson Institute concluded that the seeds of many common weeds that invade the garden are stimulated to germinate when exposed to red or far-red light even for only a fraction of a second. Furthermore, the weed seed studies concluded that weed seeds may remain dormant in the soil for 40 to 60 years. Better news is that the viability of weed seeds under a natural environment decreases with time. In other words, fresh weed seeds have a higher percentage of germination than old weed seeds.
    This information should be an incentive for us to purchase LED headlamps so we can garden in the cool of the evening or early morning before sunrise. Do not use headlamps with conventional light bulbs because common light bulbs emit red light.
    Our soils are loaded with millions of dormant weed seeds waiting to germinate in the right conditions. Cultivating the soil during the daylight hours with a rototiller, hoe, rotary hoe or hand-pushed cultivator exposes those weed seeds buried below the surface to the sun’s rays. These rays are rich in red and far-red light, thus satisfying the dormancy requirements of many of the weed seeds and prepping them for germination.
    By cultivating the soil in the evening or early morning hours wearing an LED headlamp you will be minimizing weed seed germination because the LED light emits only blue, which has no effect on the light-dormancy requirements of the weed seeds. LED headlamps are lightweight and generate an abundance of light to work by. Because the bulbs are light-emitting diodes, the batteries last a long time.
    This year we have had an over-abundance of rain, making it especially difficult to control weeds. Often the soil has been too wet to cultivate or hoe, especially silty soils of clay loam.
    If you find yourself being overpowered by weeds, consider using the weed eater or lawnmower to prevent them from going to seed. In gardening, we must always be thinking of next year. The better we can do in controlling weeds this year, the fewer weeds we will have next year.