You are so very welcome!
"The Boxwood sounds promising, and I'm going to continue researching it...but it sounds like it's a very slow grower, and I wonder how long it would take to create a complete hedge."
It would take 2 to 4 years to fill in depending on how close you plant them and what the growing conditions are.* The better prepared your soil, good watering practices and the more sun, the faster they will grow.
"I'm still leaning toward the Dwarf Yaupon, especially since it appears to be more of a horizontal grower as you said.* Hopefully this means it would quickly fill in the gaps and create the hedge I'm looking for."
The same conditions apply.* I would say that the dwarf Yaupon holly will grow more horizontally and probably fill in the gaps a little quicker, but you will need to space them accordingly as well.
"Is there a standard distance a) from the house, and b) from each other when planting hedges, or can I assume it depends on which shrub one chooses?* Sounds like 2 feet away from the house and about 3 feet apart would be appropriate for the Dwarf Yaupon Holly, but I'm wondering if there's a generic rule of thumb out there..."
Planting 2 feet from the house for the Yaupon is kinda close as this tends to grow wide and you'll be doing alot of trimming to keep it away from the foundation.* You really should space them so they are at least 12" from the foundation at maturity.* The closer you space them to the house, the more you will have to prune.* They want to mature at 7' to 10' wide or even wider.* If you space them 5' from the house you won't have to prune them for a long time.* When given mature size by a grower or a nursery, the generally accepted length of time is at years of age.* So figure that whatever you plant it will be the suggested size in 10 years.*
A good example is the dwarf Alberta Spruce.* Most sites you will search will say they mature at 5' to 7' tall over a long period of time.* I've seen ones that are 30 years old and they are 20' tall and more.* It's really a matter of that 10 year maturity and knowing the plant material.* Many trees and shrubs are labeled 'dwarf' or 'nana' but they still get taller then what you are told, they just grow slower and/or have a smaller habit such as leaves or stature.
As far as planting close to each other, it would probably to search for the particular plant as a hedge to find recommendations for spacing.* Here's what I just did to find this site. The first pic is an informally pruned hedge and the last is a formally trimmed hedge. I went to http://www.google.com and put in the search box:
Ilex vomitoria 'nana' + hedge
You could also search with:
Ilex vomitoria 'nana' + hedge + space
Ilex vomitoria 'nana' + hedge + spacing
If I haven't answered all your questions just lmk.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.