According to the ASPCA, yes. Here's what the ASPCA has to say:
Additional Common Names: Starflower
Scientific Name: Borage officinalis
Toxicity: Toxic to Dogs, Toxic to Cats
Toxic Principles: Tannins, mucilage
Clinical Signs: Vomiting and diarrhea
Tannins and mucilage aren't significant toxins but we have no manner in which to know how 1000 mg would affect your spaniel. I would induce emesis with 3% hydrogen peroxide dosed at 11 mL (two measuring teaspoon) per kg of body weight. He should vomit within 15 minutes. If not, please repeat the same dose. Please respond with further questions or concerns if you wish.