Garden sponges (also known as vertical mulching) are a great way to keep trees and shrubs watered in New Mexico’s dry climate. This is especially helpful with our sandy soil which doesn’t hold water well.
The concept is very simple:
1. Dig a pit 1 – 2 feet away from the tree or shrub you are planting.
2. Fill the pit with biodegradable material that will break down and hold water: straw, junk mail, old phone books, paper waste, old clothing, etc.
3. Cover with straw or other mulch to keep your garden looking pretty.
4. Fill the sponge with water
Here are some photos of a sponge that I created adjacent to a new Pomegranate tree.
I dug the hole about 16” from the tree. The hole is a foot deep, a foot across and 2 feet wide. I have my garden “claw” in the hole to give you an idea of how deeply I dug.
I used the soil from the hole to create a berm around the sponge and the pomegranate tree. The berm will help keep water near the tree where I want it.
You can dig a hole big enough to fit a straw bale, or a foot square –just enough for junk mail. If you are planting a tree that will grow very large, you may want to create a sponge near the base of the plant –to provide moisture while the tree is growing- and one several feet away that will tend to the plant’s growing roots as it gets bigger. And hey, while you’re at it, plant one on both sides.
It takes a lot of junk mail or old bank statements to fill a hole –trust me. I had saved a pile of old clothes that were too ragged to take to the thrift store or use as rags. These were gone in no time.
My first layer of sponge materials were paper recycling: old journals, scrap paper, grocery store circulars.
My second layer included clothing (all those old shreddy bandanas I just couldn’t part with).
Next came green material (weeds, garden trimmings) and then a topping of spent hay from the goat pen.