My Ball Blue Book says:
Select Young tender tips. Wash thoroughly and sort into
sizes. Trim stalks by removing scales with a sharp knife.
Cut into even lengths to fit freezer containers (Zip-Loc type
freezer bags work great) Scald small spears 1-1/2 minutes,
medium spears 2 minutes and large spears 3 minutes. To scald
use 1 gallon water per pound of vegetables. Put vegetables
into blancher (wire basket, coarse mesh bag or perforated metal
container) and lower it into vigorously boiling water. Begin
counting the time as soon as vegetable is placed in the boiling
water. Keep the heat on high and stir water, or keep container
covered during blanching. As soon as scalding is complete, the
vegetables should be cooled quickly to stop the cooking process.
This can be done by immersing the vegetables in ice water.
They should be stirred several times during cooling which should
not be longer than the scalding time. Drain and pack in freezer
bags. Seal; label; and freeze immediately.