Black Walnuts - Great Taste But a Tough Nut to Crack

This photo is of black walnuts forming in early spring.  The nuts grow in pairs and have a green outer coating. They'll continue to grow until they're about the size of a small plum or golf ball. But don't let the size fool you. The green outer coating is about a half inch thick and when it comes off, there's a hard shell underneath.  The size of the black walnut without the coating is about the size of an English walnut.

The leaves on black walnut trees are one of the earliest to drop in the fall, leaving the nuts easy to spot. Once you identify a black walnut tree, you can check occasionally to see when the nuts are beginning to fall (they don't all fall at once). 

If you leave black walnuts on the ground, their green coating begins to turn brown.  Be careful picking up walnuts at this stage because this brown coating will stain your hands.

The walnuts in this photo have fallen and are just beginning to turn yellowish brown and then dark brown. 

If you leave the nuts on the ground even longer, the brown coating begins to dry and won't be as soft and messy. However, the longer you leave them, squirrels may take them away or falling leaves will cover them so you can't find them again.

Whenever I go walking in the woods or where I know black walnut trees are, I always carry a bag or bucket and pick them up, even if they still have the green outer coating on them.  I don't take chances that they'll be there when I come back.

If black walnut trees are near a road, cars often run over the nuts and break off the coating.  Then you only have to pick up the nut itself.  Unless they've completely dried out, you'll want to wear gloves so you won't stain your hands brown.

You can also remove the outer coating by putting the nuts in your driveway and driving over them; your tires will only break open the outer coating, not the actual nut shell.  Don't use your driveway if it is made of concrete, though, because the brown walnut coating will stain it.  And don't leave the nuts in your driveway if you have squirrels in the area.  A friend left her nuts in the driveway overnight and by morning they were all gone!  She could see squirrels in the trees eating them. 

If you don't use your driveway, you can remove the outer coating by putting the nuts in a bucket or trash can and the coating will come off on its own once it dries out.  Shuffle the nuts around now and then for air circulation.  You could also spread them out on some newspaper in a screened-in porch or in your garage, again, shuffling them around now and then to let air get to all parts of the nuts. 

Once the outer coating is removed, you'll need a hammer to crack them.  Black walnut shells are the hardest shells of any nut tree. Once you crack the shells in half, you can put them in a bowl and use a nut pick to get the nut meats out at your leisure.  If you let them sit open for a day or so, the nut meat will dry slightly and be easier to pick out.

This seems like a lot of trouble to get black walnuts, but they have a wonderful taste and I love getting free food!

If you don't have black walnut trees growing in your area, you might find them in some grocery stores, Farmers' Markets or health food stores. You can also order black walnuts online.

Because of their strong taste, black walnuts are not usually eaten as a snack, but are used in baked goods and candies. And of course, walnuts are a healthy food.  They contain copper, manganese, magnesium and phosphorus.  14 nut halves have around 185 calories.

 Black walnuts contain a chemical called "juglone", which causes sensitive plants to struggle to live or even die. The flower buds have the most concentration of juglone, but it's also found throughout the tree, including the roots. The roots of a black walnut tree often grow three or four times the diameter of the tree’s canopy, an extremely wide area. The toxic effect of juglone also depends on the soil's texture and drainage. Even if you cut down a black walnut tree, the juglone toxicity often stays in the soil for several years, especially if the roots are are still in the ground.

All other walnut trees and including hickory, pecan and shagbark produce some juglone, but not nearly the amount produced by the black walnut.  The juglone produced by these other trees won't have much effect on plants growing underneath them.  If you're buying walnut trees, watch out for walnut trees that have been grafted onto black walnut rootstock.

Plants Sensitive to Juglone from Black Walnut Trees:

Tomatoes seem to be the most sensitive to juglone.

Other sensitive crop plants are asparagus, rhubarb, potatoes, cabbage, eggplant, and peppers.  Sensitive flowers are flowering tobacco (nicotiana), petunias, buttercup and narcissus. 
 
If you need to plant near a black walnut tree, try raised beds with some type of screening at the bottom so the roots won't invade the bed (you'll need to make sure you have good drainage).  Also remove nuts and debris as they drop from the tree. 

Composting: To be on the safe side, compost black walnut leaves separately from your other compost and don't use this compost on sensitive plants such as tomatoes.

CAUTION:

Horses have shown sensitivity when black walnuts chips or sawdust was used for bedding material.

The black walnut tree used to grow in the eastern bottomland forests in the United States. Trees were often 150 feet tall with 6-foot diameters. Early colonists exported the wood to England from Virginia in the 1600s.

The black walnut tree is heavy and strong.  Wood was used to make all kinds of furniture, flooring, coffins, and especially gunstocks. It was extremely popular 1830-1860, but by then, the wood was becoming scarce on the east coast.

But in the Midwest states, black walnut was still abundant, although the largest trees were already gone. The wood was often used for split rail fences and railroad ties.

As veneers became popular, black walnut lost its popularity until the 1970s, when prices went sky-high.  Even today, it's quite valuable and forestry officials often are called on to track down walnut poachers. In 2004, DNA testing was used to solve one such poaching case, involving a 55 foot (16m) tree worth $2,500 U.S.  (Information from Wikipedia).