The branch will not grow new needles where needles have dropped off.

The branches on Thuja o. 'Degroot Spire' if completely brown are dead. Inside brown patches on a other wise healthy branch is normal. Conifer is just cleaning out old growth that is not needed or not getting enough sun.

Sounds like your Degroots are just adjusting to the new planting area. In time they will settle in and quit browning. In your case I think the conifers are slightly stressed.

Bottom line: Make sure they get enough water and don't fertilize.

Dave

In more general terms, most conifers won't re-grow after being cut back into old wood that has shed the leaves, but a few will:

Pine family Pinaceae:
ÂPines: a few (Pinus canariensis, P. pinea, P. rigida, and one or two others); most don't though.
ÂDouglas-firs: Pseudotsuga macrocarpa does to a limited extent; others don't.
ÂSpruces: Picea sitchensis does to a small degree; most others don't much if at all.
ÂFirs: most don't, or only do so to a very small extent.
Cypress family Cupressaceae:
ÂSequoia sempervirens, Metasequoia, Cryptomeria, Taxodium, Cunninghamia, and one or two junipers do
Âmost others (including most junipers) don't.
Yew family Taxaceae:
ÂYews: all do
Araucaria family Araucariaceae:
Âmost do, including Wollemia.

Resin

Resin. "Most don't." That pretty much covers it, especially in his case, considering what he is growing.

Dave

Yep . . . you'd already answered "thinking of two specific genus" so I did the next bit "but am interested generally" ;-)

Resin

Resin, Thanks for for the additional information to the post.
I am sure some of us weren't aware, with the exception of the Taxus family, that there are a few conifers that would regenerate foliage when cut back to old wood myself included.

Dave

Actually Douglas-fir of both R.M. and coastal subspecies produces epicormic branches that bear new needles. These arise from buds buried in the bark of branches which have died, and form the basis of crown replacement in old growth. Larches, notably European, alpine, and western larches do likewise. So do Sitka spruce and blue spruce.
Pinyon pines, shortleaf and pond pine can be added to Resin's list, and just about any juniper will put out new shoots bearing juvenile foliage as response to trauma. Firs too -- lots and lots of conifers.

Oh wow, that's amazing info! Does this mean that if I leave my douglas firs alone (the few that have had the most of the west sides wiped out this past winter and look bare on that side), that they will re-grow and fill in again?? I was going to have the landscaper just replace them this fall, but maybe I won't have to if this is true!

Afraid not. In Doug-fir it is a characteristic of old trees growing in natural habitats that are very different from the pampering that planted trees get.
Next time you are in old-growth Doug-fir, redwood, or giant sequoia, look up the trunks of big old trees and you'll see groups of radiating thin branches that seem much too small for huge trunk origins. Those branches originate from buds that were on the base of a big primary limb that died and eventually falls away. Then the bases of the small limbs get overgrown by the trunk, but survive an unknown time.

Thank you, Dave, Resin, and pinetree 30. Very helpful, and interesting. I'll heed the advice.