When I was summoned through the covenant to fight a single player while having the young grass dew I noticed my Fp was raised from to 233->256, Poise 37,51->43,76. Absorptions varying, but nearly 7,00 each to both physicals and elementals. Every single resistance gained 33 points each regardless of their original value. Also I noticed that a summoned spear will always spawn homing soul mass -type of projectiles (5 pieces), but now that I had the young grass dew the count was 6.
I did not check if there were any changes without the item, but as far as I know a spear shouldn't get buffs without it against a single player.