Wow, lots of info online. Here is a photo showing the color inspiration, however mine will not be this shape. Also, one article mentioned Spring being the best time to plant the hedges, but Fall has worked out for me in the past. Now this year it may be different tho because of this summer's drought.

It would be great to find true dwarf boxwood but I have never seen this but once, and I have two intermixed with some wintergem boxwood. You can tell because the foliage is much smaller and it grows much slower. I used it to replace two boxwood plants that had died. Lowes advertises Dwarf Boxwood but to me it looks completely different.

Would Lonicera nitida 'Baggesen's Gold' work?

Annette

Interesting, Annette! Never saw that shrubby plant before, it could be contender. I'll write it down.

You know I just remembered that Barberry is deciduous, at least mine loses its leaves in winter. The Lonicera apparently keeps its foliage, which might be interesting in winter depending upon the design I create with it. I was thinking nothing very elaborate.

Carytoperis worchester gold
Dwarf spirea like "Double Play" (name Monrovia has given it), golden elf, goldmound limemound....

They probably need more consistent pruning than the lonicera but might fill in faster.

have you tried a mountain gem boxwood? It was developed up here in Ontario to withstand our cold winters. I wouldn't say it's a dwarf form but it grows small. It has narrow leaves. Of course all topiaries and hedging materials always needs to be pruned so for as long as you keep them pruned, they will remain small.

Also boxwoods are relatively easy to grow from cuttings. So if you can stand the wait, do cuttings now, put it in a cold frame and then plant them out in the spring. I saw this on a Geoffrey Hamilton (British Gardener/prsenter) do this while preparing a knot garden from scratch.

Ianna

Baggesens Gold will still need clipping. RHS says 1 - 1.5 metres but mine gets to 5 feet high and wide before I hack it back. It is brighter on the new growth so clipping helps with that. And to me it is more gold than chartreuse. And is it hardy in z5? Sources here say 'fully hardy' but that means down to 5f (-15c). Do you get colder than that? It's evergreen for me but I believe it loses its leaves in colder places. On the plus side it is stupidly easy to grow from cuttings so you could bulk it up very quickly.

Santolina virens 'Lemon fizz' might be a possibility but again I am not sure it is hardy enough. What about another berberis eg Berberis thunbergii 'Aurea nana'

Here is a link that might be useful: Lonicera

Topping this post, as I recently spoke to a nurseyman about my choice of shrubs for this project and he suggested a dwarf barberry called "Concord". He said his has begun to replace the Pygmy Crimson Barberry at his nursery with the Concords. However, they are a bit expensive at $20 each. The Concords are a nice dark crimson and will stay at a dwarf height much longer but still require pruning. He also brought to my attention that any crimson barberry must grow in mostly if not full sun to retain it's dark red color. If not, they tend to green up - like mine in the sunken garden. In fact, any red plant does better in full sun. I didn't know this.

So I will have to put this knot garden project on hold until next season so that I can afford the Concords. I'm still noting all your suggestions for the green portion of the knot. Thanks.