Hedges or covered walls can send pollutants over your head
Plants can capture or send dangerous particles away from your save-haven sensory garden.
A well-designed garden can create a pollution barrier that can provide some relief for those who suffer when dangerous pollutants and irritants in the air.
Why not just a fence?
A fence can force air carrying dangerous particles higher and over your head, but a living fence is much more effective. The reason for this is that a living fence--in addition to forcing air over your head--also captures particles, which offers a greater advantage to your health.
An Evergreen or a Deciduous barrier?
The ideal green barrier depends, as always, on your climate and needs. Consider what grows best in your area and can best withstand limitations such as drought, etc. Also, when are dangerous or irritating air particles the worst where you live. For example, where I live, winters are the most dangerous time to go outdoors if you suffer from heart or lung disease as it tends to have the most dangerous air particulates. For that reason, evergreens may be the best option for year-round protection. a row of dense trees can also create a barrier.
If you want to speed up the process, consider a fedge over a fence or vines up your wall
A fedge is a hedge covering up a fence. Plants will be able to climb more quickly if they have a structure to support them. So instead of just a boring fence, let some green take over.
If you are in a hurry to protect your sensory garden and you already have a well, growing vines to climb up a bare wall is a great way to quickly add the benefit of plants to capture those air particulates.
Protective hedges can be beautiful
A hedge does not have to be uniform. Feel free to vary the colors and textures to make it add an extra element of beauty and privacy to the garden. Take advantage of the "rooms" that your hedge may create in your sensory garden. The hedges or covered walls will soften the corners of your garden making it look less harsh. If you do it right, having a special place for those who have heart and lung disease and who can sit and relax is the best possible scenario.