I have had a tree in my backyard for years and have watched the green "seeds" grow and fall each year without knowing what the tree was. The squirrels knew as did other wildlife, but I had never identified the tree and discovered the secrets inside this tree.
For me, this is unusual as I am curious about everything and yet missed a great lesson in growing vegetables and flowers. This particular tree is central to a small habitat that I have and use to attract birds and other critters. It has the in-ground birdbath, (See the post on ants swimming), the hummingbird feeder, and the suet feeder for the woodpeckers and other clinging birds. Of course, squirrels also like to try to get to the suet but that is another story. But, it is an area that I have tried to grow several types of flowers including annuals and perennials. But most failed and I was perplexed to say the least. I had some success with Impatiens and Morning Glories but everything else that I tried died fairly quickly. So, I set out to find out why I was having so much difficulty with this area. And, it all started with this tree in the cover photo.
I began by identifying the seed, or in this case the drupe. (The outer fleshy part containing a seed). I determined that the tree was an Eastern Black Walnut and that it has some very interesting chemistry. Black walnut drupes contain Juglone, (Ju Glone) which is 5-hydroxy-1,4-napthoquinone, yellow quinone pigments, and tannin. The juglone is an alleochemical, a biochemically active material that has an influence on the growth of other living organisms including plants, bacteria and fungi, and even people. Alleopathy can be either positive or negative, and in the case of the flowers I was trying to grow, it was having a negative effect. But, we  know that there is what is called "companion gardening" where one plant can be beneficial to another.The area that was not conducive to growth in my case extended from the expanding roots to the drip line of the tree. So, if I had identified the tree sooner I could have saved a lot of time and energy. This is a lesson well-learned.
But, that is not the end of the story of black walnuts. The liquid portion of the drupe is brown and stains everything that it comes in contact with and has been used as a dye for centuries. The tannins react with iron and can make a good quill ink. There is a post from the Ohio State University Extension Service on toxicity and some of the plants that will grow with the black walnut tree here. I have also included the following photos of black walnuts in various stages of ripeness as well as the ripe inner edible fruit:

Frequently as we make plans to start a new project or build the next gadget, we have to think about where we will acquire the necessary parts. Some of us already have boxes of stuff around, but, if you are anything like me, they are poorly organized. I know that I have at least one of everything needed but do not know where it is. So, I look around in my list of web sources for the parts and pieces. I began to assemble a list for this page but found a really good site that already had a better wheel. So, rather than reinvent said wheel, I will add a link to the site. Sometimes, it is smarter to buy first quality items, but in many cases, surplus is cheaper and will work as well. But, I use caution as there are times when surplus does not mean cheaper. So be careful when ordering surplus parts. There are some sites I use regularly and can safely recommend but will not endorse. The Electronic Goldmine has been a reliable source with frequently good buys. American Science and Surplus is good for odds and ends, bizarre, and one-of-a-kind items. They also have a fairly good selection of laboratory glassware. But, check the prices! Some are higher than at other sites. Sometimes for electronic projects in a hurry, Radio Shack is a good possibility. But, the prices are high and selection is limited. Electronic kits are also readily available if you like to solder. Velleman has the greatest choice but Carl,s Electronics is also a good choice. They provide the instruction manual in pdf for many products if you want to see how it works first and see the complexity of the build.
The site is the property of krkaplan and he has done a fantastic job of collecting sources. I clicked on several sites and the links are active. It was updated in 2012. Check out the kits section and there are many of the now defunct kit makers like Heathkit and Allied. But, these are an historical perspective and there are modern kit suppliers listed. You can find it here. A tip of the hat for Mr. Kaplan!