Planting herbs at Ostara is something I have done to satisfying effect in the past. Depending on what my general aims are for the festival I either hang on to them or have also given them away as gifts if I want to replenish energies around me (it's important to remember that energies are all about balance - giving and taking). However, I do not plant them on Ostara itself but at the full moon which this year on the 30th.
While using moon phases is an old Pagan method, it is still used in many agricultural areas today so is far from being restricted to witchcraft spells! It's about the gravitational pull of the moon as well as the amount of moisture in the soil. So consequently, this part of my Ostara spell and ritual will be delayed until the full moon.
However this does not mean I do not have a few plans for beforehand. There has been a lot of rain for us lately and so if this continues I will be collecting rain water a couple of days before I plant the seeds which I'll use to water them.
I also like to decorate the pots and trays on Ostara itself so that I get the feel of the festival right. If I manage to come up with something half presentable, I may even post my efforts!
As I mentioned before, I've opted for mint, parsley and basil for my herbs this year. I've chosen them on the basis that I like them to be honest but mint is a very popular herb to plant at Ostara or to use in cooking if your rustling up a feast. It has just the right fresh taste to represent the feel of this time of year :)