Module 5: Desiging in the Garden - Pea trellis

It's Spring time in the garden! Fresh green growth is coming on rapidly and it is a joy for the students to see such dramatic changes in the plants every time we go out in the garden. The little pea seeds that we had planted a couple weeks ago are now fully fledged garden plants reaching towards the sky. It is anytime now that we will be seeing the flowers starting to come out.

There has been such rapid growth that our little pea plants are in need of some support to get them off of the ground and away from all of the slugs and snails that would love to feast upon them in the early morning dew. Today, we focused our garden session on a building project. Using some simple math, basic engineering principals, and some tape measures, rulers, and pencils, we were able to successfully design and build a pea trellis for our school garden.

This is a great activity for all ages as there are many opportunities for learning. Younger students can flex their number skills as we take the dimensions of the bed that requires the trellis. Older students can be challenged with getting creative about how the trellis will stand up against the wind and be able to support the weight of the plants. You can get into some more complicated math if you choose, or just stick with some basic measuring and calculating.

 

After a discussion about what trellises are and looking at some examples (this is a great way to practice using the internet), we started our project by measuring the bed that would receive a new trellis then draw some ideas on what kind of trellis to use and how it would look in our garden. 

We had a couple styles to choose from and wound up merging the two to fit our trellis needs. There were great opportunities for so many discussions!

For materials, I had brought some plum tree cuttings and some twine. This was all we needed for what turned out to be a pretty stout little trellis.

We tied up a few of the branches together into triangles and set them into the bed. After we had a couple of those we were ready to attach the top bar where the twine would come down and support the plants. Upon placing the top bar, one student, a second grader, said; "Wait! We need x's!". She was referring to cross bracing, a very important architectural and engineering concept. This was another great learning opportunity and we paused for a brief discussion about the strength of triangles. We did a "wind" test where we all stood on one side of the uncompleted trellis and blew as hard as we could to see how much it would move from side to side. We also poked it a little to see the amount of swing that the structure had.

As a group, we decided we need more support, some of the "X's" the student had mentioned. So we went back to work measuring and cutting our cross braces, then tied them up. After we had our extra support on we did another wind test, and gave it another poke.

Viola! A stout and Sturdy pea trellis.

Things to consider:

• materials can be simple - The plum branches used in this project came from my neighbors weekend pruning. 
• students can measure and cut how long the twine should be to reach down and grab the pea plants, put posts in the ground, and help to tie all of the pieces together (have an adult double check the tightness of the knots)
• you can get very involved in math and engineering and discuss the geometry in addition to the physics behind this kind of structure
• The trellis can also be used to showcase bird feeders in a garden that might not otherwise have a good place them.
• You can design an experiment to see if plants will grow the same amount if the leading twine is vertical or at a slope