If you use machine washable fabric and trim; make detachable skirt (and definitely make the sleeves detachable!) and construct the clothing to survive the machine, you can go full length and hang the impracticability, safe in the knowledge that you can get mud of of the bottom 12” of skirt.
Many fabrics, including wool and silk, claim to be hand wash or dry clean only but can be machine washed if you prewash before sewing.
If the skirt isn’t detachable, you can think about stuffing the bodice part into a pillow case or mesh wash bag to protect it, and secure with a big rubber band.
The outer dress in this picture (bodice and skirt, but not the sleeves) went through a washing machine three times over about four years, due to excess mud. I did ‘pre-wash’ beforehand by hanging it up over the bath and using the shower spray on the hem.
The gold underdress was made out of curtain fabric and has been through the washing machine countless times.