I've never seen a grafted Red Flame. Highly likely it's true scion.

You may have the same issue we do. Excessively warm winter/spring days push growth too soon and the new shoots get whacked. Mine I didn't protect got frozen back three times this spring, usually just once, and now those plants may be dead. But they were fine until they started to grow, no winter die back.

The grapes I protected from 24F May 3rd mostly look very good. One may have taken damage to the unprotected trunk. It has been wilting but should heal I think with probable loss of fruit.

fruitnut:
Good to hear that the 'Red Flame' may not be grafted & the huge green shoot that just appeared from ground level may truly be the 'Red Flame'!! Will let it grow to see what the leaves look like & will be sure & protect it this winter & next spring until I determine if it is or is not the 'Flame'! The "Flame' from last year that grew so well & was trailing over some trellis, had long vines.of healthy leaves .... and all were dry/ dead this spring!

We have some very old (more than 45 years old) 'Concord' seed grape vines that have withstood minus 19 degrees here in the 70's & bear heavily of those delicious old flavor grapes! I planted a seedless 'Concord' last year too & am anxious to see how they compare to the seeded 'Concord' in flavor! Had to prune back both the fig & pomegranates too as they froze this last winter also so another year til they will hopefully bear again from the new growth now coming.

Flame has somewhat distinctive leaves. I'd bet a hundred bucks you've still got Flame.

Just checked my freeze damaged Summer Royal, 24F May 3, and the inch diameter trunk is dead. No green under the bark. But it does have strong growth from the base so I'll let that grow. Mine are all own rooted just like every grape I've ever grown.

Yes, the 'Red Flame' grape leaf is rather distinctive so will see what kind of leaf this shoot coming from the ground has. For sure this growth will be delicate this year so I will really insulate it this next winter. Thanks for some encouragement!
So many things that are grafted are not worth keeping if new growth from beneath the graft is the only growth. I just had to prune the fig & the pomegranates (ouch! the 'pomes are SO 'prickly!) way back almost to the ground where I see some green growth... but the whole tops are dead from last winter temps. Neither were grafted.

The green shoots from the ground are vigorous & growing up to where I now can train them on the wires & the old dead vine. They are so green & tender though so will have to really protect them this summer & next winter; hope I can get some grapes to form so I can tell if they really are the 'Red Flame'! I refuse to give up!

I had four grapes froze back to the ground in May. They are sending up shoots from below ground. Just can't keep those grapes down.

The grapes that I protected from that freeze, 24F, suffered severe damage to the unprotected trunk. They are healing and growing slightly. Most of the berries aborted. All are sending up shoots from at or near ground level.

A related note:
Two of three 'Black Monukka' large vigorous vines I planted last year appear to be dead, while one is trying to put out a shoot, but is quite pitiful. All are in same south-facing area where my 'Flame' has done well for several years.

'Black Monukka' supposed to be hardiest European table grape, but I don't believe this anymore. So far 'Reliance' hands down appears to be the best for here, precocious and productive as well. I don't think I'll try any other European table grapes in my climate.

The new growth from the roots is SO vigorous this year & I am kept busy trying to train all the new vines. Am so happy with the growth since the main vine froze to the ground last winter & sure hope these new shoots from the root/ground are still 'Red Flame'! Am hoping I could get a few grapes this year to really verify they are 'Red Flame' but will have to cover the whole new growth this Fall so it doesn't freeze again next winter!