I do think nasturtiums taste quite nasty, but I've found a way to make some use of them. (They self-seed in this garden every year, especially with the warm winters of late.)
I take the leaves, remove stems, chop them up and mix them with some chopped chives (needless to say, from the garden). I sprinkle on some salt, lime-flavored pepper flakes and add a dollop of creme freche. It's a combination of my own invention; I'm always finding some way to make up new stuff.
The taste of the leaves reminds me of the taste of unripe papayas. There's also a kind of slimy undertaste, which the combination of extra flavors and the creme freche serve to mask.
I've eaten ground elder, (svalderkaal) too. I gathered the small, new, yellow-green leaves. It would be best, I think, to remove all trace of stem. At first I simply steamed them for two minutes inside the rice cooker (above the freshly cooked rice, which stained the surface green), but since they remained quite stringy and tough (despite their tender appearance), I lighted on the barbaric act of putting them in the microwave for a few seconds, along with the butter-impostor I had tossed them with. They were easier to chew. I recommend boiling them for a short while, though.
What do they taste like? I've read numerous inquiries of this nature on the web. Lots of people recommend ways to cook this invasive weed, but nobody can describe the flavor. Well, it tastes ... good. Its merit, I think, is in the chewy texture, as most vegetables tend to be mushy even when steamed. If you grew up in Southeast Asia, you would understand this comparison: it feels and tastes like steamed camote tops. It has a flavor that is a stronger version than the scent of it as you pull it with your hands.
I can't keep digging up the ground elder; I have too much work, especially now that my stay in Denmark's coming to an end, so I just look out for new growth and eat it as it emerges.