I think it kind of depends on the type of shade you have. Is it deciduous or building shade? Is it high-filtered shade. Does it get any bright light? It doesn't sound from your post that there is much sun at all on either side, so I would think that there would only be minor differences between the two sides. However I wanted to mention that when I moved to my current home I had mostly sun, no shade trees. I soon found that heucheras did not do very well in solid building shade, the only kind I could provide. Right now, except for some lime green ones, which will scorch a bit in the sun, I grow most of my heucheras & heucherellas in the sun. I'm talking about 6-8 hours or more of sun. Peach Flambe is spectacular looking in sparkling sunlight & may be bright enough to show up well in darker situations. I just don't know. The dark purple-red heucheras blend into the dark ground color too much for my taste. Pewter Veil does nicely for me in bright light (no direct sun) & looks especially nice with the silver-green Lungwort Majeste, along with the slow-growing Japanese Painted fern & a big fat Bergenia cordifolia Bressingham Ruby. I also have 4 varieties of the Caramel/amber ones (the best of which is Caramel) and they color well in both heavy deciduous shade and sun, being just a bit greener in shade than in sun. The ones in shade are a lot smaller, but that may be a varietal thing as some of the early amber ones were poorish growers. OTOH, I wanted to mention to you that I gave away most of my purple varieties to a niece with a new-to-her home in an older neighborhood. She has huge big limbed-up-high trees providing lots of filtered light & they are all doing well for her. They are doing much better for her under the trees than they did for me in the dark building shade. Hopefully, some people with shade will post their experiences for you.

If you want aggressive groundcovers that spread quickly - but don't invade or affect your larger plants - I have a few I like to use, which are common, easy to find and well-known: Ajuga reptans var. 'Bronze Beauty' - nice dark-leafed groundcover (a mottle of dark purple and olive green leaves) that is very shade-tolerant for the areas closest to the house. Short blue flower spikes in the spring. It will survive droughts but if there's water available it will grow very dense, to make it absolutely impossible for weed seeds to sprout from within it. But it's shallow-rooted so won't compete with your plants, nor will it shade them because it never grows more than 3 inches from the ground. It's easy to spread around by digging small bits that take well even in heat. Sedum spurium 'Red Carpet' - A very attractive red-leafed sedum that will really stand out in contrast to those varigated irises if planted right next to and among them. It is also very low-growing, drought-tolerant so it will not take water that could be going to your other plants, and this particular variety grows pretty slow. Sedum spurium 'Tricolor' - similar to 'Red carpet' but grows more quickly, has a green/white leaf that has a very visible pink blush over it when it's exposed to direct sun; it also turns more pink in the winter, and has pink flowers. Cerastium tomentosum ('Snow In Summer') - spreading silver-leafed ground cover that is also reliably less than 4 inches high, gets absolutely covered in white flowers in the early summer, and would pop against the ajuga and red-leafed sedum. It wouldn't contrast as well against the iris so I wouldn't plant it right there, but because it's the most drought-tolerant, I'd put it right up against the edge of the garden.

Yes, you can collect seeds but it has taken a LONG time for the seed pods to dry on my Heauchera's. They bloomed in June and I have just collected the dried stalks. For me, this flower's seed is too small to try to work with and I just strip the whole stalk of flower pods, dry it some more and save the whole mess. In the spring I will crush it a bit and sprinkle everything into jugs - the seeds are in there soemwhere. Worked really well with both Palace purple and Venus last year.

I have the same condition...areas of my driveway garden get sun from about 12 pm to 3 pm...(full shade in before 12 pm and dappled light after 3 pm.) Probably the hottest part of my garden, it's a 6' strip between the house and asphalt! I'm having success in that area with every hosta I've planted there: guacamole hippodrome wide brim moonlight I'm not the best at watering, but this area is close to my hose spigot and it's the first area I hit with water, so I've only gotten a touch of burn on the guacamole when I was gone for 1 1/2 weeks in July. I use full-sun companion plants in that strip: sedum, rudbeckia trilobum, beebalm...it's fun to have the hostas with sun loving companions. Same area but slightly shaded by a large airy arborvitae: krossa regal hadspen blue halcon Pulmonaria did not work for me, either, I tried it under the arborvitae, they really like more water. If you want an awesome cover, try bigroot geranium...I have that mass planted across many areas: full sun, full dry shade, the area by the Krossa Regal I just mentioned, under maples...it is my absolute favorite perennial for ease and beauty...after hostas, of course. Not invasive at all but fast growing. I use it as filler in pots, too. Here is a link that might be useful: geranium macrorrhizum