Missouri State Tree Nut - Black Walnut
published on: 2/28/2003
Contributing Teacher(s): Calene Cooper
Science/Life Grade Range: Middle Grades (6-8) Materials Needed:
Grade Range: Middle Grades (6-8)
- Goal 1.1 develop questions and ideas to initiate and refine research
- Goal 1.2 conduct research to answer questions and evaluate information and ideas
- Goal 1.3 design and conduct field and laboratory investigations to study nature and society
- Science 1. Properties and principles of matter and energy
- Science 3. Characteristics and interactions of living organisms
- Science 5. Processes (such as plate movement, water cycle, air flow) and interactions of earth’s biosphere, atmos...
Time Allowance: Minimum of 3 class periods
Description: This lesson from a six lesson unit deals with the Missouri Symbol of Black Walnut.
Comments: This lesson is one of six lessons of a complete unit.
Classroom Component: Teacher Note: This lesson is a part of a complete unit. Click on the links below to view other individual lessons. Lesson introduction page State Flower--Hawthorn State Fish--Catfish State Aquatic Animal--Paddlefish State Mineral--Galena State Rock--Mozarkite Procedures:
- Black Walnut Toxicity
In Roman times it was noticed that walnut trees had a poisoning effect on many plants. The plant yellowed, wilted, and eventually died. Today we know that the causal agent is chemical which naturally occurs in all parts of the black walnut. The chemical called juglone (5 hydroxy-1, 4-napthoquinone) has been shown to be a respiration inhibitor which deprives some plants of the needed energy for metabolic activity. The largest amounts of juglone occur in the buds, nut hulls, and roots, however the leaves and stems do contain a smaller quantity. The poison is poorly soluble in water so it does not move very far in the soil. Some sensitive plants may tolerate a certain amount of juglone if they are far enough away from the tree''s roots, but may not survive directly under its canopy. Even dead trees still release juglone through the decaying roots and the toxicity can persist for years after a tree is removed. Gardens should be located away from black walnut trees or a raised bed or rock wall between the tree roots and the garden can help minimize the toxic effects. Leaf litter, walnut husks, or twigs, bark, wood chips of black walnut should not be used to mulch landscape or garden plants nor should they be composted.
An interesting activity for a field experience could be to explore the plants that are sensitive to or tolerant of the juglone toxin produced by walnut trees. Students can make careful observations in their neighborhoods or natural areas attempting to identify these two groups of plants. Below is a table that will help in this activity.
Plants Sensitive to Juglone Plants Tolerant of Juglone Vegetables: cabbage, eggplant, pepper, potato, tomato Vegetables: lima beans, snap beans, beets, corn, onions, parsnips Fruits: apple, blackberry, blueberry Fruits: cherry, black raspberry Landscape plants: black alder (Alnus), azalea, basswood, white birches, Hopa crabapple*, hackberry, Amur honeysuckle, Japanese larch, lespedeza, lilac, saucer magnolia, silver maple, mountain laurel, loblolly pine, red pine, scotch pine, white pine, potentilla, privet, rhododendron, Norway spruce Landscape plants: red cedar, crabapple*, elm, winged euonymus, forsythia, hawthorn, hemlock, hickories, black locust, most maples, oaks, autumn olive, pachysandra (spurge), pawpaw, persimmon, wild rose, sycamore, most viburnums, Virginia creeper Field crops: alfalfa, crimson clover, tobacco Field crops: white clover, red top grass, orchard grass, soybean, timothy, wheat Flowers & herbaceous plants: autumn crocus (Colchichum), peony Flowers & herbaceous plants: bluebells, Kentucky bluegrass, daffodil, daylily, ferns, fescue, iris, Jack-in-the-pulpit, liriope, narcissus, phlox, poison ivy, Shasta daisy, trillium
- Harvesting Black Walnuts Black walnuts are hard to crack, they must be removed from their hulls and the amount of nut meat per kilogram of collected walnuts is low. However, the delicious taste of walnuts and the experience of harvesting and processing this crop is something that all Missourians should try. The nuts are ripe when the hull can be indented with the thumb or there is some degree of softness. Some authors caution that walnuts should be hulled and cleaned while the husk is still green. Waiting until the husks is black and mealy increases the possibility of rotten nuts. While there are commercial walnut hulling machines available for use in the fall, simpler and effective devices can be home-made. A simple walnut huller can be made from a piece of 3/4 inch plywood cut to 6 by 20 inches in dimension. Drill one or two 1-5/8 inches (3.5cm) holes in the center of the plywood and place it on top of a metal bucket. After placing walnuts on each hole, hit them with a wooden mallet to shear off the husks. This should work reasonably well with practice. If you have only a few nuts, place them on a concrete surface and step on them to break off the husks. At this stage, the nuts can be cracked, however the moisture content is usually too high. Instead of cracking them immediately they should be stored in a dry place for about 2 months. This will cause the nut meats to shrink inside the shells making the meats easier to remove later. If you do crack the nuts before drying, you should allow them to dry for a week in the cracked state before attempting to remove the nut meats. Most people collect and hull walnuts in October and crack them around mid-December. Black walnut shells are very hard making a standard nut cracker useless. There are heavy duty black walnut crackers or one can place several nuts in a strong bag and hit them with a wooden mallet. Be careful not to crush the nuts. Harvesting the nut meat pieces can be made easier if one does it systematically. Separate whole nut meat pieces in one pile. Place pieces of shells in another pile. A third pile should consist of nuts that require recracking. Use a standard nut pick or meat skewer to remove the nut meat. Sift the harvested nut meats on a piece of screen or kitchen strainer to help remove small pieces of dirt or shell. Allow newly shelled nut meat to dry for two days before refrigerating. You can store shelled nuts in a refrigerator or freezer for up to two years. There are many different recipes available using black walnuts. Walnuts can be added to baked goods; cookies, cakes, muffins, breads, candy, and waffles. They can be used in cheese spreads, sauces, dips, salads, and as toppings for casseroles. To roast nut meats, spread them on a baking sheet. Heat at 350oF for 5 to 12 minutes, stirring occasionally. Walnuts are rich in food value, they are a source of several vitamins, including thiamine, vitamin B6 and folic acid. Minerals include; iron, zinc, copper, magnesium, phosphorus, and potassium. They are low in sodium and have substantial amounts of dietary fiber. Walnuts contain about 14.1 grams of protein per 100 grams of eatable nut meat. Most of that protein is digestible, making walnuts extremely valuable to nutritionists as a food that has a high protein quotient. It is an excellent source of protein for vegetarian diets. Walnuts contain no cholesterol and are high in unsaturated fats. Walnuts contain 70% polyunsaturated fats, 58% being linoleic acid and 12% linolenic acids, both essential for good health.
- Walnut Shell
Crushed walnut shell is a hard fibrous material used as a soft abra
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