Mariana fern, Thelypteris torresiana, got its name because it is native to the Mariana Islands. It’s not often seen for sale, although Goodness Grows carries it. It was first discovered naturalized in Florida and has spread north into Georgia.
Mariana fern, also known as Torres Fern, is expensive at the nursery, but the return on the investment is extremely high. Mariana fern is tolerant of just about any growing situation, including dry, poor soil. So long as the soil is not packed clay Mariana fern will expand rapidly via rhizomes.
Mariana fern is reportedly invasive in some areas. In my experience, it does not spread aggressively via spores, but it will spread throughout the immediate planting area via underground rhizomes. I have always been grateful for every single stem. The first time I saw this fern it was planted directly in front of the Institute of Ecology at the University of Georgia.
It pulls up easily and is easy to remove from the garden. It generally stays restrained in the area you plant it. There are some plants, northern sea oats, for example, that can be very difficult to eradicate if allowed to go to seed. Worse, once sea oats get dug in, you have to dig it out with a garden fork or spade. Thankfully, you can pull up Mariana fern with a gentle tug.
Ideally, you would plant it where it can spread among other plants, or perhaps naturalize in areas of the garden that don’t get a lot of your attention. One or two plants will begin to form a colony within a couple of seasons. Supplemental watering should only be required the first year.
Hardiness is at least to zone 7b, and Mariana fern is tolerant of most exposures except direct prolonged sunlight. Grows to 3-4 feet and spreads (fairly aggressively). Extremely easy to grow.
| Genus/species | Thelypteris torresiana |
| Common name(s) | Mariana maiden fern, torres fern |
| Of note | tough fern that covers ground steadily – don’t plant in beds with perennials that can’t compete – beautiful fern, one of the most beautiful |
| Fall color | insignificant |
| Water requirements | drought tolerant, average, moist soil conditions, high |
| Soil quality | rich, well-drained, average |
| Suggested use(s) | groundcover, naturalized, shade gardens, understory, woodlands |
| Hardiness zone(s) | 7b, 8a, 8b, 9a, 9b |
| Type | herbaceous perennial |
| Native | no |
| Invasive | yes |
| Deer resistant | yes |
| Deciduous or evergreen | deciduous |
| Flower color | non-applicable or insignificant |
| Bloom period | insignificant or not applicable |
| Exposure | afternoon shade, filtered light, full shade |