we had temperatures in the low 20's. my plants have extensive brown discolored leaves. should I prune back to the ground?
Prune off the dead growth, but leave anything with some color still. It will take nutrients back out of these to put up fresh growth.
they have been doing fine but a hackberry tree has recently been taken down and there will be more filtered light come summer
I don't see your cast iron plant in the photo. Is it on the porch?
Cast iron plants are pretty tough, hence the name. Nevertheless, they are shade plants, so you may need to move them. I'm sure some filtered light is fine, but not full sun all day.
https://www.gardeningknowhow.com/houseplants/cast-iron-plant/outdoor-cast-iron-planting.htm
I have a huge area of Cast Iron plants. From the center of the bed, something is chewing off the leaves at the bottom of the stems close to the soil. In the middle of the planting bed, there are no leaves left. They are cut off at a slant. What could be doing this? The plants are being grown in the ground in North Texas.
Sounds like the work of a critter, possibly a rabbit. These articles may help:
https://www.gardeningknowhow.com/plant-problems/pests/animals/camouflage-gardening.htm
https://www.gardeningknowhow.com/plant-problems/pests/animals/plants-rabbits-dont-like.htm
My long search for Canadian suppliers stocking interesting aspidistra cultivars, with dramatically variegated foliage, has been unsuccessful so far.
Unfortunately, we do not recommend specific sources for purchase. I could suggest trying sources, online, if you are willing to take the risk. I have had many successful purchases online, and many unsuccessful ones!
What I can do is direct you to a few links to help you with the care of the plant:
https://www.gardeningknowhow.com/houseplants/cast-iron-plant
Several cast iron plants were planted in the shade of oak trees last October. We subsequently experienced a low temperature of -8 in an atypical winter storm here in North Central Texas. The once-green leaves are now totally tan, though some of the stems are still green. What should I do now: trim back to the green stems, replace the whole plants, leave the plants alone and see what happens?
They should be hardy to zone 7, which is to 0 degrees F, so doesn't bode well for -8 temps. However, since you see green, I would wait it out and see if they return from their roots. If you see new growth coming up, you can trim off the old growth.
https://www.gardeningknowhow.com/houseplants/cast-iron-plant/outdoor-cast-iron-planting.htm
My new indoor Aspidistra 'Shooting Stars' got mealy bugs, I treated with a bug oil and popped it outside for the day while the bugs 'hopefully' all died. I then gave it a shower the next morning to wash off the oil residue and any dead or surviving bugs. The older leaves on the plant now look very dark and leathery and appear to be dying, the younger leaves appear ok so far. What should I do?
I suspect the combination of bug oil and trip outside didn't fare well with the plant. Cast iron plants are usually pretty tough though. Often, houseplants don't like to be moved. I would trim off the worst looking leaves, and give it a drink and a light fertilizer. It should bounce back.