Hortus III lists around 100 different species in the northern hemisphere! 'Froebelli' is a cultivar like 'Anthony Waterer,' both of which are crosses of Spiraea albiflora and S. japonica. 'Snowmound' is a cultivar of S. nipponica (Tosa spiraea). There are innumerable crosses and variations within different species of spiraea. But of the three you listed Froebel and Goldmound tend to have unbranched to lightly branched stems where Snowmound is branched with heavier stems. As far as shade tolerance, A. W. has tolerated considerable shade in my yard, but certainly does fine in full sun. There are undoubtedly others with good shade tolerance. A. W. is slightly smaller than Froebel at maturity but has more intensely colored blooms. Disease-wise, a few feet from the A. W. all of my Snowmounds have been affected by what I'm guessing to be bot canker, two have died and the other three are so badly damaged that they will be shovel pruned this spring. The A. W.'s are not affected by this at all. I also have a hedge of S. x vanhouttei and a single plant of S. prunifolia in the yard that are not affected, leading me to think that Snowmound is a weaker species. Snowmound gets much taller than the other two, but the time from planting to mature size is probably similar. Spiraeas are generally pretty tough plants for this area (and many others!). hortster

I'd lean towards Magic Carpet or Goldflame. Do they have very intense burgundy spring foliage? Magic Carpet is so common but its one of the best. Stays a bit more tidey and has very vibrant spring foliage. I use to be a spirea nut, just because they where so easy to grow and adaptable to various soils, exposures and moisture. Snowmound was by far the worst of them all. They are in my top 5 worst shrubs that can be grown in my area. They suffer from dieback and thin out. Double Play Artist is probably my next favorite spirea. I thought I recall it being a superior variety over AW. And my third is Tor Spirea. All others are inferior in my opinion.

Hedges often have much closer spacing than would be used where fully developed specimens would be intended to end up just touching one another. Or overlapping to a much lesser degree than within a dense hedge planting. If you have bought them already try laying the plants out and seeing what seems to you to be an adequately close spacing at this time. To a certain extent when they are to meld together into a dense row you really can't put the plants too close together. Of course, if you start out with them absolutely packed together at a small size there is some likelihood of stunting occurring later due to the crowding.

I have several plants that are repeated in my own garden and the public gardens where I work. My go-to plants must be highly deer resistant and must endure hot, dry summers (the historic site garden is not irrigated). My list is as follows: Walker's Low nepeta, Siberian iris, bearded iris, peonies, Sheffield chrysanthemum, artemesia, stachys and daffodils. This year, I'm going to give geraniums another try: in the past they were eaten. A group of archers has been conducting winter hunts in the green space near my home for several winters and the deer population is slowly beginning to drop.