When a person eats pumpkin seeds or watermelon seeds, which Beracha should he recite? Do we consider the seeds part of the pumpkin or the watermelon, such that one should recite "Bore Peri Ha'adama" just as he would when eating pumpkin or watermelon itself? Or, do the seeds constitute a separate entity, thus requiring the Beracha of "She'hakol"?
The Shulhan Aruch (Orah Haim 202:3) rules that with respect to Berachot, Halacha treats edible seeds of a fruit as part of the fruit itself. In his view, then, one would recite "Bore Peri Ha'adama" over pumpkin seeds or watermelon seeds. This ruling represents the view taken by many Rishonim (Medieval Halachic authorities). However, the Rashba (Rabbi Shelomo Ben Aderet of Barcelona, Spain, 1235-1310) was of the opinion that seeds comprise a separate entity, and thus require the Beracha of "She'hakol," rather than "Ha'adama." In deference to this position of the Rashba, the Hid"a (Rabbi Haim Yosef David Azulai, 1724-1807), in his work Birke Yosef (202:3), ruled that one should recite "She'hakol" over seeds. The Hid"a applied here the principle of "Safek Berachot Le'hakel" – that one should never recite a Beracha when there is some uncertainty as to whether it is warranted. With regard to seeds, since the Beracha of "Ha'adama" does not fulfill one's obligation according to the view of the Rashba, one should recite "She'hakol," which is effective for all foods, even those which ideally require a more specific Beracha.
Hacham Ovadia Yosef, in his work of responsa Yabia Omer (vol. 7, 31), observes that the prevalent custom follows this ruling of the Hid"a, requiring that one recite "She'hakol" before eating seeds. He writes, however, that one who wishes to recite "Ha'adama" in accordance with the Shulhan Aruch's ruling may do so. Hacham Ovadia explains that even the Rashba would agree that one who recites "Bore Peri Ha'adama" over seeds has fulfilled his obligation, even though he maintains that one should preferably recite "She'hakol." Therefore, since the recitation of "Ha'adama" fulfills the requirement even according to the Rashba, one who wishes may follow the ruling of the Shulhan Aruch and recite "Ha'adama."
Rabbi Moshe Halevi (Israel, 1961-2001), in his work Birkat Hashem (vol. 3, 7:13), adopts a different position, claiming that one should ideally recite "Ha'adama" over seeds. He contends that since nowadays there is an entire industry marketing seeds for consumption, and orchards are planted specifically for the seeds, even the Rashba would consider the seeds that are packaged for eating as part of the fruit. Hence, under today's circumstances, all authorities would agree that one should recite "Bore Peri Ha'adama."
As for the final Halacha, it would appear that the more prevalent practice is to recite "She'hakol," though one who wishes to recite "Ha'adama" may certainly do so.
It must be emphasized that this discussion does not pertain to sunflower seeds, over which one must certainly recite "Bore Peri Ha'adama." Sunflower seeds constitute the actual fruit; nothing else grows with them. Thus, they clearly require the Beracha of "Ha'adama."
Summary: The more prevalent practice is to recite "She'hakol" over seeds such as pumpkin seeds or watermelon seeds, but those who wish to recite "Ha'adama" may do so. Over sunflower seeds, however, one must recite "Ha'adama."