Some of our newly planted ferns turned brown last summer. They were pretty, and we didn’t know what we had done wrong.
We eventually learned that the fern, polypodium Californicum ‘Sarah Lyman’, or California polypody fern, is summer dormant. Wikipedia says “In plant physiology, dormancy is a period of arrested plant growth. It is a survival strategy exhibited by many plant species, which enables them to survive in climates where part of the year is unsuitable for growth, such as winter or dry seasons.” California has a Mediterranean climate with warm summers and very little rain for 6 months, a harsh climate for plants. The polypody adapted to our dry summers by going dormant.
This year we documented the polypody’s summer dormancy.
On May 30 the polypody is looking good. The fronds are 1′ tall, growing in the shade of a coast live oak tree, quercus agrifolia.
A month later, the polypody is fading fast.
Two weeks later, the polypody is brown. We subsequently cut up the fronds and left them as mulch.
But in late August, fronds begin to emerge from the leaf litter.
And shoots continue to emerge two weeks later.
California has a tough climate for plants, with little rainfall during the warm summers, when plants need moisture the most. Some California native plants like the polypody have adapted by going dormant during the summer.