Black Walnuts

Black Walnuts

When I was growing up, a neighbor had a large black walnut tree growing right near the edge of our yard. Each fall we would try to beat the squirrels to the nuts that fell on our lawn. We would carefully remove the husks and crack the nuts to use in baking. It was a lot of work but kind of fun too. And yet, many gardeners are careful not to plant black walnut trees in their yards. Lets see what we can find out about this tree. 

Do you have any black walnut trees in your neighborhood? Take a look at this Web page to find out what a black walnut tree looks like. The easiest way to find a black walnut tree in the fall is to look for the tree’s fruits. Black walnut trees have big, green,ball-shaped fruits that have a hard nut inside them. You will see some of the green fruits on the street or ground underneath them and hanging on the branches.

Black walnuts are hard to get into to eat. The green outside layer or husk can stain your hands brown when you try to remove it. Inside this layer is a very hard nutshell. The Minnesota Extension Service has suggestions on how to open and use black walnuts. 

Squirrels seem to love black walnuts. They chew through the husk and the hard nutshell and eat the nut meat inside. Since the tree makes so many nuts in the fall, the squirrels hide some of them for use later in the year. If any of these are left unused they sprout into new black walnut trees. If trees had feelings, this would make a black walnut tree happy since the real reason the trees grow these nuts is to make new trees.

It may seem strange but black walnut trees are kind of poisonous. There is a chemical in most parts of the tree that makes it hard for some kinds of plants to grow well near a black walnut tree. The roots of the tree give off a lot of this chemical. The decaying leaves and nuts also can leave a lot of the chemical in the soil right under a black walnut tree. This means that next to a black walnut tree is a poor place to try to have a garden. Scientists have a name for when a plant gives off chemicals that protect it from other plants trying to grow close by. It is called allelopathy. 

Some animals are also sensitive to the chemical made by black walnut trees. If black walnut shavings are included in a horse’s stall, the horse can get hoof and leg problems. A dog playing fetch with black walnuts and chewing on the green nut husks can get an upset stomach. 

Black walnut trees have complicated leaves made up of a main stalk and smaller leaflets. As the leaves drop early in the autumn, the leaflets fall off first. A little later the leaf stalks fall, leaving a tree that doesn’t seem to have very many little branches. Keep an eye on any black walnut trees you find around your home or school and see if you can watch this happen. What color are the leaflets when they drop? Why is it helpful to many trees for them to lose their leaves in autumn?

Black walnuts are just one of the interesting plants found growing in New York State. Keep your eyes open to learn more.
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