My suggestion: Study one tree, one bird, and one insect per school year.
Take it slowly. Find one tree in your yard that you can study for a whole term.
Find out what kind of tree it is.
Make rubbings of the leaves and bark.
Does it drop its leaves or does it stay green year round?
Does it have any birds in it? Any insect holes? Hollows for critters?
Can you climb up into it and see what the view is?
Can you lay under your tree and watch the branches move in the breeze?
Does it have blossoms, fruit, cones, seeds, or other objects to study?
Do you see a nest in the tree?
Is the trunk straight, crooked, twisted, rough, or smooth?
Do the leaves or needles smell good? How about the bark?
Watch and observe and narrate one thing at a time you will find that it is really not so hard. If you feel like recording the experience, put something on paper.
I don't look at outdoor time and nature study as one more subject I need to plan and be ready for, I just let it unfold. If your children want to learn more about something they find while outdoors, gradually teach them to look things up for themselves in a good field guide or on your next trip to the library.
If you observe and identify one tree per year, over the course of your child's education, you will have learned about 12 different trees...I don't know about you but I have a hard time just listing 12 trees by name so if your child has become acquainted with 12 trees, they are far better off than many of us.
Slowly, gradually, gently....it works.
So I decided to follow my own advice and I went out and found a tree in my yard that I was interested in learning about. Turns out that after examining the leaves and the trunk of the tree, I discovered my tree is an Interior Live Oak. I know there are several varieties of oaks in my yard but I have never taken the time to identify them as any particular oak. My oak has leaves with pointy edges and they are glossy on both sides. It also has pointy acorns. While I was examining the trunk I discovered that one side of it has *lots* of woodpecker holes drilled into it. I have walked by this particular tree hundreds of times but have failed to notice the holes. Amazing....now I will on the watch to see if I can see the woodpecker that makes the holes. :)
I used a tree identification guide and my new tree field guide to help me. This whole process, including taking the photos, only took a few minutes. I plan on watching my oak to see if there are any other things that I can learn about it. Interior Live Oak