Validation

I went to a meeting of the Santa Fe native plant society chapter. I'm not a joiner, I've never really gotten into garden clubs or plant interest groups, but two friends invited me and we went.

It's a really large group. I liked that the people are not plant purists. They talked about mixing exotic and introduced plants in their gardens -- how else can you have an interesting garden in this difficult climate?

But of course they value and promote using native New Mexican plants for all the well established ecological reasons, and they want to learn. I can see the benefit of a group like this, I'm just not one for meetings and bylaws and fund raising and group activities.

The speaker at the meeting, a PhD in ecology, was great. She covered all the basics about plant communities and never talked down but made it interesting. And one thing she discussed resonated with me:

She talked about humidity. Not rainfall . . . . humidity. 

She explained how plants and forests respond to humidity below 20%: they reduce biomass. 

Yesss. 

This was scientific validation of my humble observations. I've said the plants in my garden are stunted, she says they adaptively reduce biomass.

 

I like it better the way she says it.

I really liked her emphasis on humidity, because no one ever considers it in horticulture. Garden practices all focus on soil moisture (watering), air temperature (the cold zone a plant survives in) and light (full sun or shade). No one ever mentions humidity, but the stress of transpiration is a factor in our gardens where the air is at 15% humidity or less almost every day.

The soil is moist, the air is temperate, the sun is sunshiny . . . but the plant struggles as it draws up moisture through the roots, up through the stems and out into the dry atmosphere faster than it can use the water, all day.  

On the left - my sulphur buckwheat (Erigonum umbellatum) shrublet after 6 years. On the right - what it should look like in better conditions.

← mine                     sigh                   what it could be →

Well tended, well watered, nice plants just don't grow very big here.  Of course some do, like big coarse junipers and giant cottonwoods near streams, but you can't make a garden of just that. And some invasive introduced things like Russian olive have found a way to exploit a niche at this level of humidity, to great ecological detriment.

On the left - my aronia melanocarpa 'Iriquois Beauty' after 6 years.  On the right - what it should look like in other conditions.

          ← mine                      sigh                   what it could be →

It was validating to me to hear about air humidity as a real factor in how plants grow. I can irrigate, I can put plants in the right spot for sun and protect them from harsh conditions, and if all of that is done well, they are still going to be smaller and slower growing than I expect.