I've had a number of seedlings, from multiple species of oaks, bit completely off at ground level. Almost every one came back just fine. If it were me and I was sure that the terminal bud was gone, I'd go ahead and make the pruning cut down just above the next lower live bud. This is a GREAT time to make that cut, so that the wound can be covered over when growth occurs. Any setback for overall growth should be next to nil.

Headed the leader back to the first good bud. Buds are swelling and green now all along the top half of the whip, so it appears to be ready to grow vigorously this year.

Squirrels, chipmunks, and rabbits are three reasons to really protect young oak and cherry seedlings. Chipmunks will often gnaw off the young stem and dig the acorn and leave the top half lying on the ground. Squirrels will just dig the acorn and dispose of the seedling. Rabbits will gnaw off and eat the stem. Take your pick! I've had it all happen.

Really no different than late-freeze killing of emerging terminal buds, which happens to some of my oaks most springs. They just sprout more secondary buds.

I bet it won't miss a beat. Deer ravaged my 6' swamp white twice, before I finally put netting around it. I cut the main leader down to the next best bud at 4' (mid-summer) and the thing did not look like much. But it sprouted both up and out like a champ during the second flush of growth of the season.

Closeup of the top this morning. In the warm sunshine today, they have actually expanded noticeably since I took this picture about five hours ago.

9 days later, those buds have lengthened to about 3.5" for the top one, and around 2" for those below, with small leaves unfolding quite nicely

However, the presumptive "leader", The bud on the upper left, is still growing straight out at a 40 degree angle and showing no signs of curving upward yet. Will it continue growing this way for a while or will it start to turn up before the growth hardens off?

Most other trees I have done a heading back cut on, the new leader starts curving upward almost immediately.

Here is a pic of the new leader, or what should be, based on it being the topmost shoot, as well as the most vigorous.

Not the best focus, which is why my hand is behind it...to try to get better focus.

Hair, you're well ahead of me. Only my Shumard/Nuttall has slightly expanding buds -- all the rest doing little yet. As a result, my Shumard/Nuttall gets chronic freeze damage every spring.

Most oaks except Q. alba are around the same stage of growth around here as what I posted-oak pollen is all over the place in my neighborhood.

The albas are a bit behind as they typically are. Same for some, but not all, coccinea.

Happened again this spring!!! D@$&@$&!!!!

How do they reach the top of a 3' seedling???

Probably deer at that height

Agree^....it's the deer ones. Son and I planted a number of species but the swamp white oaks in particular got hammered by deer. We've since placed herbivory protection. Like dumb guys everywhere, we waited until it was just plain obvious that these oaks would not amount to anything if not protected. Meanwhile, they are pushing back very strongly and appear set to make significant growth this year.

I would normally agree it was deer - however - these plants are in fabric containers on my deck. A deck that has no outside stairs and is only accessible off the house. There's no way a deer could get there, unless he/she can jump 15'.

Just bought and moved to a new house, so they're in pots until I take inventory of the yard this spring to see where I want everything to go. I have 1 acre, not as much as I wanted, but workable.

Some birds will pick off terminal buds.