Saskatoons and junipers

When it comes to berry-picking around Kimberley, huckleberries are far and away the most popular fruit to harvest even though the Saskatoon bush is one of the most common shrubs in the area. The Nature Park is full of Saskatoon bushes, but it is fairly rare to find one laden with great fruit for picking. There`s a reason for that.

Gymnosporangium bristles protruding from ripening Saskatoon berries.

If you have ever had a close look at some of the berries on our Saskatoon bushes, you may have noticed some rather icky-looking bristles poking out of many of them. In addition to being an instant turn-off to berry pickers, the little bristles are the spore-producing bodies of the Gymnosporangium fungus. Look closer at the plant, and you will see coloured spots on the leaves and tiny bristles projecting from their undersides as well.

Leaf-spotting on a Saskatoon bush caused by the fungi.

Spore-producing bristles on the underside of Saskatoon leaves.

Gymnosporangium, of which there are several species, is a fascinating resident of the Park. It makes its living by killing the cells of the Saskatoon and ingesting the nutrients. One of the neatest things about this fungus is that the spores it releases from the little bristles on the Saskatoons cannot infect other Saskatoon plants. The only plants Gymnosporangium spores can successfully colonize are members of the juniper family.

When the spores are released and blown by the wind, to successfully germinate and grow they must land on the stem of a common juniper or Rocky Mountain juniper. They will grow into the juniper stem and wait until spring rains provide enough moisture for the next stage of their reproduction. In May, when conditions are right, orange jelly-like fingers called telial horns emerge from the stem of the juniper, and these produce a new kind of spore that now must infect Saskatoon bushes.

Telial horns growing out of a common juniper near Myrtle Junction.

A closer view of telial horns on a juniper branch.

Once again carried by the wind, the spores alight on the leaves and buds of the second host plant, and by July the Saskatoon berries and leaves will be well-infected. Since the Nature Park is home to lots of juniper and lots of Saskatoon bushes, it will always be a great place for Gymnosporangium to grow. Keep your eye out for it the next time you go for a walk in the Park.