When is the best time to shape a boxwood plant?
This article should help with that: https://www.gardeningknowhow.com/ornamental/shrubs/boxwood/trimming-boxwood-bushes.htm
My boxwood (3) shrubs are planted as a border between properties and get the morning sun. They were planted two years ago and this spring they have yellowed on the top....not looking good. Can they be saved? What can I do to make them look healthy green or is it a lost cause?
This is probably a condition caused by the severity of the past winter season; it is called winter bronzing. This article contains more information: http://www.ces.ncsu.edu/hil/hil-8628.html
Bought a small boxwood shrub. It smells like cat pee. Is this normal?
Unfortunately, yes, this is normal. Many boxwood shrubs (usually American species) are known for their overwhelming aroma that is reminiscent of male cat urine. This article will help with types to avoid when purchasing these shrubs in the future: https://www.gardeningknowhow.com/ornamental/shrubs/boxwood/boxwood-has-bad-odor.htm
Boxwoods have yellowed on top probably due to winter winds. Do I snip them or trim them now or leave them alone hoping that they will recover with more green growth this summer. How should I treat them now?
This is a condition know as "winter bronzing," and happens after unusually severe winters. While the plants should recover, they will look much nicer if you trim away the discolored foliage. This article is on trimming boxwood: https://www.gardeningknowhow.com/ornamental/shrubs/boxwood/trimming-boxwood-bushes.htm
I planted dwarf Wintergreen boxwoods two months ago. They look healthy and I am working hard to keep them watered. Yesterday, beside one of the four bushes was a pile of a yellow powder near the base of the bush. It looked like pollen. This morning that pile of yellow had grown and gotten thick and sticky. What is this? Is this normal? It is pollen or some kind of disease/fungus?
Webs in boxwoods. Why and what do I do?
The webs are probably caused by spiders or tent caterpillars. These articles have more information: https://www.gardeningknowhow.com/plant-problems/pests/insects/spider-garden-pests.htm
https://www.gardeningknowhow.com/problems/pests/tent-worms-tent-caterpillar-home-remedy.htm
For another approach to identification and possible remedy, consult with your local county extension service. This link will help you locate one:
https://www.gardeningknowhow.com/garden-how-to/info/what-is-extension-service.htm
My Buxus are living in a southwest facing windowsill, and one of them is having a growing patch of yellow drying leaves.
While it's not unheard of to use boxwood as an indoor plant, neither is it common. I don't think boxwood adapt easily to the restricted roots, weird drainage, and lowered light that they find inside houses. Because of this, they are going to be easy pickings for any number of diseases and insects. You will have to examine the leaves (undersides especially) and branches for bugs: https://www.gardeningknowhow.com/houseplants/hpgen/common-bugs-and-pests-on-houseplants.htm
Then look for any kind of spots or discolorations on the leaves adjacent to the brown area. This would signal some kind of bacterial, viral, or fungal infection. For many of these there is no treatment other than to cut out the infected area before it spreads.
There could also be a broken area on the main branch.