Author: Roberta (Page 502 of 561)

Weekend Science Fun: Tree Leaf Age

This week’s topic is, well, timely.

A few years ago my son asked how long tree leaves live. Having grown up in an area with four seasons, I always thought leaves lived from spring to autumn, when they fell off. Here in Arizona, however, we have trees that are green year around and I had no idea how long the leaves of a lemon tree, for example, might live. Then I began to wonder if trees and shrubs grow new leaves throughout the spring and summer, or whether they have short burst where all the leaves come out and that’s it.

If you’d like to find out how long the leaves live on your trees or shrubs, choose some freshly emerged leaves and mark them with acrylic marker. You can tell the young leaves because they are a lighter, brighter green color and are toward the tip of the branch.

If you don’t have a marker, you could also mark the leaves with tags or ties, anything that won’t wear or fall off or interfere with normal leaf development and photosynthesis. Record how many leaves you tag, when you tag them, and roughly where they are in the tree.

Check your leaves periodically. You might want to mark more leaves each time if you see new ones. This is a long-term project, so be patient.

We marked some of the new leaves on our lemon tree a few years ago. Our marked leaves remained on the tree through one entire year. The tree dropped a lot of leaves a couple of times, but our marked ones held on. Unfortunately, our marked leaves were lost before the experiment was finished when someone — who didn’t know about our experiment — trimmed the tree. We are going to try again this year.

Let us know what kind of tree or shrub you choose and how long the leaves last. Let me know if you think we should do a contest for the oldest leaf.

How long do you think the oldest leaf would be?

lemon tree

Celebration of Earth and Arbor Day

For a combined celebration of Earth Day and Arbor Day, my son and I went to the Desert Botanical Garden in Phoenix. A number of the cacti were in full bloom the day we went, the butterfly pavilion is open and Dale Chihuly’s glass exhibit is in place. It was incredible.

I decided a blog post wouldn’t do the photos justice, so I have posted them in a page that allows for a slide show. Follow the link and then click on “Play Slideshow.”

http://activities.growingwithscience.com/Site/Photos.html

Let me know if it gives you any difficulty. Enjoy!

Bug of the Week: Hollyhock Visitors

This week the hollyhocks will catch your eye here in Arizona. Tall, with large, striking red, pink, or white flowers, the hollyhocks are a favorite.

hollyhock

Certain insects and arachnids also seem to prefer hollyhocks.

Shiny metallic-green flies were resting on the leaves this morning.

long-legged fly

Aren’t they pretty?

long-legged fly

Any ideas what they were doing?

Called long-legged flies, the small green flies are predators waiting to catch other insects for food.

leafhopper

Tiny, pale green leafhoppers like this one are a meal for long-legged flies.

Another fly I found isn’t quite so welcome.

leafminer fly

leafminer fly

This tiny yellow and black fly is an adult leafminer. The fly will lay its eggs in the hollyhock leaves. The larvae will feed between the upper and lower surface of the leaf causing a winding light-colored tunnel. Fortunately the damage is relatively cosmetic (looks only).

leafminer damage

Other creatures already hard at work on the bottom leaves of some of the plants are spider mites.

spider mites

spider mites

The spider mites make fine webs like spider webs, hence the name. In our hollyhocks, the mites quickly build up, causing the leaves to turn yellow and die.

Hopefully, some predators will show up that eat spider mites. Here’s a sign that at least one predatory insect is about to make an appearance. Do you know what the stalk is?

hollyhock

I’ll give you a hint:  it is on the underside of the leaf (I flipped it over).

hollyhocks

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