It doesn't hurt to apply bloodmeal when the ground is frozen. Most of the nitrogen in bloodmeal is released by bacterial action at the soil surface and takes some time to be effective. As the soil thaws, rain will wash the bloodmeal down into the soil surface and begin the breakdown.

I applied bloodmeal two weeks ago, also in zone 6b, right on top of the hay mulch between my garlic rows. By now it should have been rained down to the soil surface and "activated". This is in addition to the 5-4-3 organic fertilizer I raked in at the time of planting in November. I'll apply more bloodmeal in early April and early May, then stop.

Each feeding is at the rate of 50 lbs as N per acre, or as Bloodmeal 2.5 lbs per 250 sq ft. If the garlic looks a little pale come April I'll likely double that feeding.

TomNJ/VA

To WC Thomas
Thank you for your most helpful reply. Just before receiving it, I went out to my garlic bed on this wonderful, 57 degree day, removed a bit of the straw mulch and spread the Blood Meal. Later when your response arrived, I found that the recommendation I followed was within a couple of ounces of the application rate you suggested. I did return some of the mulch in preparation for our predicted N.Easter this week. I will follow up with two more feedings in April and May. I have been growing from the same original planting of German and Polish hardneck for about 15 years. They now all look and taste the same (quite nice). I have had concerns as this was the first time I went into the winter without 6 to 10 inch sproats growing up through the mulch from my late Oct. Planting. Local folks here blame it on the quite dry conditions in November .
Thank you kindly, once again.
Victor

Garlic is considered a LEAFY vegetable, so it can benefit from N more than P. K is also beneficial.

The reason for NOT applying fertilizers in winter months is that garlic roots won't take up any nutrients, as it does not take up any moisture to deal with the freezing cold. But as soon as it it resumes growth, fertilizer is needed.