I should add that the weather here in March-April is in the 40s-50s, although we've been known to have snow and freezing temps in early March. The construction work should take 6-8 weeks.

When I've moved plants I take as much dirt with the root ball. Place them in a Shady spot and covered with a tarp after thoroughly moistening root balls. Ck once weekly for moisture. I kept 30 boxwoods alive this way with zero loss. When they are replanted, it will improve odds to apply root stimulator in planting hole b4 plopping plants into holes. You can do this and save your azaleas.

Thank you so much. I live in Northern Virginia. It only takes about a foot of digging, or less, and you hit hard, red/orange clay. I actually wonder if that's why the previous owners (who had the azaleas planted by professional landscapers) had the flower beds built up so high.

I like the idea of using big black plastic bags with holes poked in them, and taking as much dirt as we can get with the root ball.

What do you think in terms of timing? Will early March be okay if the temps are mostly above freezing? Or should we wait until end of March? I'm actually planning the construction start date around these plants! LOL They are my favorites...

The later the better also the quicker you replant the better. So whatever dates create the shortest gap out of ground is ideal but i don't anticipate problems.

It really could go either way, but in NoVA early March would actually be a better idea. There is a greater risk of extreme high temps in April, but moreover not a risk...a likelihood...they will try to start growth by then. What you don't want is they start growing, then we have an April heatwave. In other words they are better able to handle the usually paltry cold of March when dormant, than the possible heat of April when in growth and having had their roots cut.