I found this to be interesting - I wasn't aware that caution should be given to adding these leaves to the compost - here is the article https://www.argusleader.com/article/20081028/LIFE/810280306/1004/life
Summary - black walnut leaves produce a chemical called juglone that can inhibit the growth of, and even kill, certain other plants. Tomato plants are of special concern.
Juglans cinerea (Butternut Tree) also produces the same chemical in a significant amount. And to a somewhat lesser degree, Juglans regia (English Walnut) does too. I believe Pecans, Shagbark, and Shellbark hickories also produce juglone but not any amount of consequence.
I don't know how on the money the author of that article is. Juglone is a toxin but it breaks down when exposed to air, water, and decomposition bacteria which means that in theory they should be able to be used in compost. I routinely toss Black Walnut leaves in my compost and have been for years with no ill effects. We can still mulch leaves from these plants into our lawns if we're concerned. They never seem to bother grasses in the least.
Based on my personal experiences, there are a lot of plants that are juglone tolerant. Tomatoes allegedly aren't and shouldn't be planted anywhere within the drip zone of any black walnuts, butternuts, or English walnuts. I kept my tomato plants far away from my black walnuts at the advice of friends.
Should mention that the very popular Asian honeysuckles we all know and love from our youth have a chemical that is far worse in that it inhibits germination as well as growth of many other species well beyond the drip zone. Even after one removes these species from their property, the allelopathic chemicals continue to cause problems for several years until at such time as the chemicals wash down to lower soil levels. Leaves of Asian honeysuckles should probably never be used in compost because the chemical is very different and doesn't degrade as readily as juglone. There are other introduced species that are equally allelopathic. North American native honeysuckles are not allelopathic. So many people have entire lengths of Japanese honeysuckles and they have issues getting many plants to grow in and around them and chalk up plant mortality to their own inexperience but not necessarily so. The planting of many species in close proximity to these plants usually means over time susceptible newly introduced plants will begin to decline and can die.
I don't know how on the money the author of that article is. Juglone is a toxin but it breaks down when exposed to air, water, and decomposition bacteria which means that in theory they should be able to be used in compost. I routinely toss Black Walnut leaves in my compost and have been for years with no ill effects. We can still mulch leaves from these plants into our lawns if we're concerned. They never seem to bother grasses in the least.
Based on my personal experiences, there are a lot of plants that are juglone tolerant. Tomatoes allegedly aren't and shouldn't be planted anywhere within the drip zone of any black walnuts, butternuts, or English walnuts. I kept my tomato plants far away from my black walnuts at the advice of friends.
Should mention that the very popular Asian honeysuckles we all know and love from our youth have a chemical that is far worse in that it inhibits germination as well as growth of many other species well beyond the drip zone. Even after one removes these species from their property, the allelopathic chemicals continue to cause problems for several years until at such time as the chemicals wash down to lower soil levels. Leaves of Asian honeysuckles should probably never be used in compost because the chemical is very different and doesn't degrade as readily as juglone. There are other introduced species that are equally allelopathic. North American native honeysuckles are not allelopathic. So many people have entire lengths of Japanese honeysuckles and they have issues getting many plants to grow in and around them and chalk up plant mortality to their own inexperience but not necessarily so. The planting of many species in close proximity to these plants usually means over time susceptible newly introduced plants will begin to decline and can die.