Useful Non-food/Non-material Providing Plants

One of the things Sepp is well known for is extended observation of what nature is doing and applying what is learned to the land. I have no doubt that the wealth of knowledge he has gained in this manner is beyond what most people could learn in their lifetimes. Still, I have a question not dissimilar to that of Daniel Kern in the Plants thread. While that question is more general, this one is a bit more focused. I would like to know what Sepp and/or Zach think are some of the most useful varieties of plants to add to a permaculture (under whatever name) system that don't provide immediate or obvious benefits to the humans living there. That means they don't offer any form of obvious food or material value, but do provide an amazingly helpful benefit when integrated into the overall design. Already Zach has mentioned water lilies as being a major aid in preventing water loss in periods of extreme heat, which made sense but wasn't something that would have come right to mind when setting up a pond. I think this sort of plant often gets overlooked despite its value because of the fact that they don't provide anything immediate to the property owner and insights from those who know better are a huge boon.

Pioneer species, nutrient miners, and other fertility building plants are all essential parts to a permaculture ecosystem that don't provide immediate human value. Often these plants will provide an additional resource of some type but things such as willows to stabilize banks and provide shade for water features are important elements even without the material resource. Clovers, vetches, broad leaf plants, flowers, all provide valuable ecosystem function even without having an anthropocentric yield. Bamboos and grasses can help stabilize spillways and dams. Aromatic blooming plants can draw pollinators in early in the year to be later available for fruiting crops. Cover crops provide valuable soil building and stabilize earthworks. Lots of cover crops are also great at breaking up compacted soil and adding organic matter. Decomposing radish tubers provide valuable habitat for spiders to breed. Lots and lots of different functions everywhere you look.

Already I have learned something new! I never knew that about the radish tubers as a habitat for spiders. Thank you for your response!

Native wildflowers from your region will provide both food and habitat for the native pollinators, as well as the other 'critters' that help establish a balance for your system.

Trees and shrubs that produce "inedible" berries for humans often provide food for the birds. With a hedge of a variety of these surrounding your orchard area, you may cut down on the losses of your fruits. These same birds will help reduce the insect problems, while adding nitrogen to your soil.

Every new species that you can add (especially native species) will help construct the chain of a healthy soil food web. Each species has its own piece that it adds to the puzzle. There is no native species that has no value to your system. Some are just more obvious than others.