Hello again and thanks for waiting.
Sorry to hear your dog is unwell, however I have worked out an answer for you ...
1. Wisteria is in fact toxic to dogs, you can check this out at the ASPCA poisonous plants database HERE
2. Exposure to wisteria will cause vomiting but hopefully from what you have told me so far yours will be a minor case because the seeds and pod where not actually swallowed. This a gamble of course but with minor cases you may be able to handle things on a home remedy basis. Here are some ideas ...
A. The likes of Pepcid may well help to settle your dog's stomach, follow this link for more information including dose rates etc. LINK
B. If the Pepcid settles his stomach then try to tempt him to eat by feeding him four or five small light meals in the day. These meals should be the likes of chicken, fish, scrambled egg etc. with a little rice. If he picks up on this diet gradually reintroduce his normal diet over the next few days.
Of course if any of the above does not quickly start to work or if he deteriorates further in any way you should have your vet check him over just to be on the safe side.
I hope I have covered your question fully enough but if you would like further clarification or to talk things over a bit more then I will be on-line for the next hour or so and I will be more than pleased to continue working with you.
Please be kind enough to rate my service to you after we have concluded our dialogue, such feedback helps me maintain the quality of my answers.