We moved into a new house in March 2014, so we've been here less than a year and beside our pond is a magnificent Gunnera. However, I've no idea what species it is. It grew large leaves in summer of about 2 ft across, which have now clearly died off and are brown and crispy dry. They are still, however, well rooted and firmly attached to the base. I've read articles saying the leaves could have been cut off before winter and used to protect the crown but now I'm nervous to cut them, especially where to cut them, top bottom or middle. Can you please advise whether I should cut them or leave them into spring? Thanks in advance.
Winter isn't over yet, so to protect from possible freezes, go ahead and cut the leaves now and pile them over the plant. Don't be nervous about cutting - they are just leaves and stems, same as any plant, even if they are a hundred times bigger. Cut the leaf stems near the point where they emerge from the rest of the plant. This article has more information: https://www.gardeningknowhow.com/ornamental/foliage/gunnera/growing-gunnera-plants.htm
I have a full sun area in my yard that stays very boggy due to an aerobic septic system. I have seen the great gunnera and was told it prefers wet boggy soil so it would be perfect to help keep this area dry. I have 3 large dogs that have been known to chew on anything I plant in the backyard, including barberry bushes. Is this plant toxic for dogs?
Based on my research it doesn't appear to be toxic to dogs:
However, when it comes to beloved pets, I always strongly encourage pet owners to verify this information and see if they come to the same conclusion.
What hardiness zone will Gunnera grow/overwinter in?
Gunnera is winter hardy in zone 7 and warmer. In the cooler part of this range, they benefit from the protection of mulch (or their own cut down leaves) during the winter. In zone 6 and colder, the roots can be dug up and stored in a cool, dry location for planting the next spring.
Are the roots of a gunnera plant known to become intertwined with the water system of a house?
I don't know whether this plant commonly has damaging roots, but it's certainly plausible since its root system is quite large. This is something to have an expert check on in case it is causing damage.
These articles might be relevant:
How deep does the planting medium?
The Giant Brazilian Rhubarb prefers deep moist soil.
Here is a link with more information.
My gunners is being eaten by something, the leaves look as if they are being eaten by caterpillars. What is it and how can I stop this?
There are not really pest issues associated with Gunnera.
If you have snails or slugs; this could cause this damage. Since they feed in the night they are rarely seen.
You could set out bait to see if the issue disappears.
I would also suggest treating the plant with Neem Oil. If there are pests on the plant, this treatment should take care of most insects.
Make sure you treat the top and bottoms of the leaves.
what can I do
After all danger of frost has passed, prune away the damaged leaves.