The leaves of the Black Walnut emerge in the mid to late Spring, when the last frost has long since thawed. The leaves are intensely aromatic, like ginger, cardamom and nutmeg. As the leaves grow, their flavor mellows a little. They have such a divine scent that you may want to carry it with you, everywhere. One traditional use is to hang mature leaves in the airing cupboard or wardrobe to impart a splendid fragrance onto hanging clothes. The leaves make a fantastic spice to flavor sugar and salt.
In the middle of the Summer, the fruits of the Black Walnut reach the first edible stages.
For pickling, the unripe fruits must be tender and the shell inside completely undeveloped. To test this, carefully slide a skewer (or knife) through the centre of the fruit. If the skewer meets any friction, then the nut shell is too advanced and the result will be poor. Fruits that are too far advanced can be used for flavoring. They have an intoxicatingly delicious aroma which is perfect for infusing into syrup, vinegar, alcohol, honey, sugar or salt. It is a flavor you will want to carry with you into the winter. In Italy, unripe walnuts are used to make a black colored drink called Nocino (not-chee-no).
Nuts are food for many different wild animals and have been used as a food for time immemorial. Recent findings prove that Native Americans enjoyed the pleasures and health benefits of the Black Walnut well before recent colonization. The upper Great Lakes region provides archeological evidence of walnut consumption dating back to 2000 BC.  No doubt they were used long before this too.
The nuts of this prolific tree are an exceptional source of nutrients and are widely available. The Black Walnut boasts higher levels of protein than any other tree nut and holds an impressive balance of essential fats, carbohydrates, and fiber as well as bone-strengthening manganese, cancer-fighting selenium and cholesterol-reducing omega-3 fatty acids. You can follow this link to a complete breakdown of the nutrients:
Since this tree is so widespread in Eastern North America and offers an abundant, healthful source of food, we should surely revel in its presence and celebrate its gifts by eating them. It’s a prime example of wild food: resilient, plentiful, sustainable and healthful. It is a food of the future.
The leaves, fruits, bark and roots of walnut trees exude juglone, an allelopathic (plant-killing) chemical which prevents many plants and trees from having a chance at growing nearby (except species that have evolved to withstand juglone). This mechanism gives walnuts one more advantage over plants competing for a space on the ground, contributing further to its success.
Successful black walnut harvesting and storage depends on getting the nuts processed and cured before the nut meat turns rancid. Firstly, collection demands a scrupulous selection - only fruits that are mostly yellow or green are good enough (when the fruit turns fully black and rotten, the rot can quickly pass an astringent and acrid flavor through the shell and into the nut, eventually turning the nut rancid). Next, the nuts must be de-husked. On a small scale, the husk can be broken using a mallet, then the husks can be removed by hand. This process is fun and fast. Be warned that if you are removing the husks without gloves then your hands will stain black for up to a month. Seriously, there’s no getting the ink off once it’s dry, you will have to wait for your skin to shed a layer! To access the nutritious kernel of the black walnut you will need to break the shell, which is very, very hard indeed. To do this, you will need either a specified black walnut nutcracker (which is really expensive), a vice, or a hammer and a skilful swing by the wrist. After a few tries, you will find the right force and quickly develop a skill for cracking them. It rapidly becomes fun and altogether satisfying. The reward of breaking the shell is a worthy one. The nut meat is unique and delicious, particularly at the time of year when the aromas of the walnut are especially fresh.
The trees once grew abundantly in the eastern bottomland forests, where the soil was deep and rich. Trees 150 feet tall with 50-foot clear stems and 6-foot diameters were not uncommon. Now, typically growing 70 to 90 feet and 2 to 4 feet wide, forest grown trees are tall and straight with a rounded crown. In open areas, the trunk often forks into two stout limbs supporting a symmetrical, domed crown of stout, spreading branches. The bark is thick, dark brown to blackish, scaly and deeply fissured; getting rougher as the tree ages.
Leaves between 12 and 24 inches long with 9 to 23 leaflets (usually 15 to 19). Terminal leaflet often absent, which distinguishes this walnut from other walnuts and hickories. The leaflets are each 2.5 to 6 inches long, lanceolate to ovate, sometimes curved; pointed tip; finely toothed margins. Glossy green above; lighter and downy beneath. Aromatic when crushed. Turns to bright yellow in autumn. Terminal bud whitish and hairy. 
The southern edge of Black Walnut’s native range reaches from northern Florida to central Texas. It also ranges north through Oklahoma, eastern Kansas and Nebraska to southeastern South Dakota. Across the north it grows from southern Minnesota through southern Michigan, Ontario and Vermont. Since the nuts and timber are of particular value to humans, Black Walnut trees have been planted widely and they can be found well outside of their native range. It appears to have naturalized in many areas. It is, or clearly should be, a culinary staple of eastern North America.
The fruits are large, spherical, husk-covered nuts, sometimes in pairs or threes. The husk is light green, very thick and fleshy, with a roughly dotted, sticky-hairy with no seams or ridges. The seed within has an irregularly-ridged, dark brown, very thick shell which holds the edible kernel within.
The trees grow at elevations between 0 and 3,300 feet and prefer rich-soiled mesic forests and river valleys just above the floodplain. It is capable of rapidly colonizing old fields and is often prevalent along forest borders and hedgerows. It is a pioneer tree and so it depends upon disturbed ground. Being a pioneer, it also grows very tall, very quickly: a tree is capable of growing two metres upwards in its first season. Unlike many pioneer trees, Black Walnuts can live for a long time and can remain the dominant species in a stand for hundreds of years.