Round-up is absorbed through the leaves. If there are no leaves there should be no damage. Temperatures must be in the 70's during the day for RU to work. It is not technically a herbicide; it is a growth stimulator. Sprayed plants essentially grow themselves to death. Therefore temps. must be warm enough that growing is possible.

Any easy way to spray closely growing plants is to use a piece of cardboard to separate the good from the bad, then spray.

Linda

I'd recommend extreme caution. I'm zone 3a and my rasps, both red and yellow are definitely budding, so check yours again extra-carefully. Also, last September I sprayed roundup on some quack grass in a rose bed that also contained scilla for spring colour. Since the scilla had been dormant since July, I figured all would be okay. This spring the scilla where I sprayed are very sick, whereas they are healthy where not sprayed (ie right beside the roses).

If it were me, I'd spray about a 3-foot section of the rasps. If all is well, then next spring I'd do the entire row. If all goes badly, you've only lost less than 10% of your row and that should fill back in over the summer.