Fern identification and eradication
From your description and your pictures, you have braken fern. Braken Ferns have the most worldwide distribution of any ferns. The two key identifying characteristics are 1. Size, braken ferns are large ferns, waist high. 2. Braken fern fronds (the "leaves" of the plant) are triangular shaped. The frond is widest at its base, and narrows from there. This shape is seen most clearly in your first picture - the fern in the middle foreground. The fronds from these braken fern grow directly from the soil. most other fern fronds grow in clusters at the base. Braken ferns also have small hairs on the undersides of the fronds. This is a good explanation of identifying our NW ferns, A Guide to Ferns of the Pacific Northwest https://intocascadia.com/2016/10/28/an-easy-guide-to-ferns-of-the-pacific-northwest/
Braken ferns have rhizomes deep in the soil which makes them fire resistant - and harder to control. To control them you need to force the plant to use up the nutrients it has stored in its rhizome. A safe way to do this is to mow the fronds back to the ground in early summer. You can also pull them. Allow the ferns to regenerate a 2nd crop of fronds, using up some of these stored nutrients. Mow or pull again. This will deplete the fern's resources, reduce spore production, and allow more light to get to grasses and plants under the fronds. This process takes persistence, pulling/mowing any that you see in your garden area. Sometimes being stubborn is a good trait in a gardener.
Glysophate solutions sprayed on fronds now, in early summer will also work. Follow up with a second treatment if the ferns unfurl new fronds . Glysophate is non-selective, though, and will kill any plants it touches. Use long-sleeved shirts and pants and chemically resistant gloves. Always carefully follow directions for proper dilution and instructions for application. This article has information on braken fern control, Western Braken Fern https://www.growsmartgrowsafe.org/Documents/IPM/8_16brackenfern.pdf.