what causes "helmet head"...???

[Phaeton]

My seedlings had the hulls attached while my daughters did not.

We checked for differences, same dirt, same seeds, same garden, same jiffy pots, same table, same pointy end up.
Everything was the same, except.
My seeds were planted about a quarter inch deep.
Her seeds were buried a full one half inch down, occasionally five eighths inch.

It seems my worries about sinking the seeds too deep for them to ever find daylight were totally without merit.

 

[Betterhaff]

I think seed depth is important in helping the seed shed its coat. Usually when it sprouts you get the “∩” exposed first, the stem protruding from the root end curved back into the ground to the embryo. The forces pulling the embryo up and out help remove the coat.

I’ve had all kinds of seed do it (helmet heads), some more than others.

 

[Dropped Cat]

Place seed at least 1 inch below surface, I've ruined plenty of
babies ripping the case off.

 

[troutman]

Older seeds tend to get it more often.

Planting too shallow also seems to cause it to be more prevalent.

I just use tweezers and a needle to deal with it when it happens.