You need two more spellsingers to cast seed of water on you. The seeds dissapear after 10 seconds unless a new seed is added. So you really need to co-ordinate it.
Seeding nukes are sadly useless. They do less damage per mp than the normal nukes, and require a lot of co-ordination. Someone lags, and you loose a lot of mp and another 20 minutes till you can try again. You'd be better off getting all three spellsingers to just nuke damage wise. The slow for blizzard is only an effect 3 slow... not really that amazing. NC needs to make seed nukes (and the seeds as well) mp efficient. They're fun to play with... but not worth using in raids and definitely not worth using in pvp.
These lvl 70 nuker skills are really only used because of the secondary effect on raid bosses. Demon wind that spellhowlers get was great on Antharas untill they prevented it from working. Not sure if the sps skill works on the big bosses? But anyway, there might be certain other raid bosses it would be good to cast it on.