brassicias
 

do deer have to get used to a crop. they never seem to eat my greens

I've seen Deer walk right past several fields to feed far away from cover. The only answer I can think of is they smell nutrients in the chosen field that they need.

If they aren't eating your crop they are eating something and towards the end of the year, either due to the longer nights or trying to put weight on for winter they feed more.

I once planted winter Rape a little late and figured it needed a boost. I lightly fertilized with K-mag and the Deer went nuts for the stuff.

Deer have a sweet tooth, after the first frost many plants get sweet, basically they produce their own anti freeze.

I taste some of the stuff in my plots. Some varieties of Brassica have a bitter taste. "By definition, if a seed is labeled "canola" it has to have less than 30 micromoles of glucosinolates and less than 2% of erucic acid." "These natural chemicals most likely contribute to plant defence against pests and diseases, and impart a characteristic bitter flavor property of cruciferous vegetables." I'm not saying this is your issue, just an idea.

I would say yes deer need to learn to like a new planting. I planted turnip-radish 6 years ago and it took 2 years before the deer eat the bulbs. The deer eat the green leaves as soon as it came up.

I think the answer to this, all comes down to the available food supply in the area
if there is a LOT of food they can be more picky on IF they will "X" any thing
when food is less, they ANYTHING they can to get by
and you have to remember deer numbers come into play too
HIGH deer numbers , and less food, deer again eat ANYTHING, low deer numbers and less food, deer will eat what they porefer first then onto different things

add in the fact NOT all brassicia's/rape/turnips(all in the same family of plants here)
there just NOT all the same , and then the fact they tend to be bitter to most critters when growing, and DON"T become appealing till after some frosts(again pending deer nunbers deer on one farm I managed SUPER high deer numbers would eat it as soon as it came out of the ground till all gone)

SO< if there is better food farther away than your plots OR just where deer tend to be in colder times, then you plot is NOT getting hit due maybe the deer just are else where feeding on things they have been known to eat
if you folflow me here
they might just NOT know your plots is NOW good, to eat!
so yes a learning curve might be in the cards, but also, a lot again depends on overall food in the area
IS there something better they like ? Corn and beans are hard for deer to pass up in the colder weather!
and if they stick to that and then the ground freezes, your turnip bulbs and such are again maybe more work to get to than other things?