Category: News
Date published: May 06, 2020

Freezing tolerance in blueberries

Every spring blueberry growers are anxiously looking at the weather forecast. Are the buds and flowers resilient enough to withstand the low and freezing temperatures that occur occasionally. Some growers have a sprinkling installation to protect their plants but often we see fields where we don’t have this option. Does this mean there is nothing we can do?

Frost damage

Every year again we see differences in fields regarding frost damage. Besides temperature and wind also fertilization plays a crucial role in how quickly a bud or flower freezes. There are multiple possible mechanisms that reduce the freezing temperature of the fluid in the cell. By taking the right measurements, we can lower the freezing point by 3 degrees Celsius. And these 3°C can be the difference between a good harvest or no harvest.

When sugar content increases, this will have the effect of reducing the freezing temperature. A strong and healthy plant (with strong buds) will freeze at lower temperatures then a weak plant.

The freezing point is also lowered if the cell contains more ions. This can be achieved by multiple minerals like potassium, calcium, sodium, nitrate or magnesium. The minerals reduce the freezing point much like salt lowers the freezing temperature of water.

Finally there are signs in practice that also trace elements lower the freezing temperature. Particularly manganese and boron, but also zinc, copper, iron and cobalt contribute to this mechanism. Also seaweeds applications are also known to have this effect.


A protocol full of energy

Different flowering stage on one plant (on the left a one year old branch, on the right a multi-year branch).

In the blueberry protocol of Koppert, energy in the plant is the main target. The result is more regrowth, more generative buds per branch and more flowers per bud. Higher numbers are directly caused by more energy. We see that “stronger” buds are better resilient against frost damage. This is caused by the mechanism described above.

So we see a direct effect of frost on the damage of buds and flowers. Besides that we see a second, maybe even more important difference. Because the treated plants show more regrowth in the summer and fall, plants can be pruned more aggressive in wintertime. The result is that we end up with a younger plant. From young wood we already know it produces bigger and higher quality fruit. But there is another advantage of young wood. The flower buds on young wood flower on average 7 to 14 days later. And the later the flowers emerge, the less change for frost damage.

Do you want to prevent frost damage next spring, start already this year to create a healthy, energy rich plant. Koppert is using a variety a products to support this. Central in the schedule are the product Trianum and several biostimulants. Do you want to know more about the Koppert protocol or the different products, check the website or contact one of my Koppert colleagues wherever in the world you are.

By Mark van der Werf, Soft Fruit Consultant Koppert Biological Systems