When guiding a Shinrin Yoku session, maintaining a balanced atmosphere where participants feel both engaged and unrestricted is crucial. Here are some strategies I could employ to tactfully redirect conversations back to the session:

1. Soft Transition Phrases: Use non-intrusive phrases like, “That’s an interesting point, and it makes me wonder how this relates to our current surroundings,” to gently shift the conversation back.

2. Utilize Guided Questions: Asking open-ended questions related to the Shinrin Yoku experience can refocus the group. For example, “How does the air feel against your skin right now?” or “What sounds are you all noticing?”

3. Invitational Language: Instead of instructing, invite participants to re-engage with their senses or surroundings. “You’re welcome to feel the texture of the leaves nearby,” keeps the mood open and non-restrictive.

4. Shared Acknowledgment: Sometimes, saying something like, “We’re all here to connect with nature and ourselves, let’s try to focus on that for the next few moments,” can be effective and respectful.

5. Nonverbal Cues: Subtle gestures like pausing, taking a deep breath, or directing attention to a natural feature can signal a return to focus without words.

6. Time-Check Reminder: Gently mention the remaining time for the session as a soft cue to concentrate on the Shinrin Yoku experience, e.g., “We have about 20 minutes left, let’s make the most of our time in this beautiful setting.”

7. Personal Reflection: Encourage participants to internally explore what they’re feeling or thinking and how it relates to their experience in nature, offering them space to redirect their own focus.

If despite your best efforts, the conversation continues to drift away from the focus of the Shinrin Yoku session, there are two main paths you can take:

1. Let it Flow: Sometimes the organic flow of conversation and engagement can have its own form of therapeutic or communal benefit. It’s possible that the group or an individual needed this particular exchange at this moment.

2. Gentle Reminder: At an opportune moment, you could remind the group of the purpose of the session and the benefits of focusing on their connection to nature and their intentions.

Risks of Letting it Flow

1. Diluted Experience: One of the risks of letting the conversation flow unguided is that the unique benefits of Shinrin Yoku—mindfulness, being,  stress reduction, and nature connection—could be diluted. 

2. Creating Misconceptions: If participants are new to Shinrin Yoku, they might walk away with a misunderstanding of what a typical session involves, which could potentially influence their willingness to participate again or recommend it to others.

3. Disrupting Group Cohesion: Different participants have different goals and comfort levels. Allowing the conversation to stray too far from the session’s focus could alienate those who are there for a more traditional Shinrin Yoku experience.

4. Unmet Expectations: Participants come with their own set of expectations based on what they’ve read or heard about Shinrin Yoku. A session that strays too far from these expectations may leave some participants disappointed.

Your role as a guide is to balance the group’s needs with individual’s needs and the aims of Shinrin Yoku. Sometimes letting the conversation flow might be what the group needs, but it’s crucial to weigh that against the potential risks. If you decide to let it flow, you might consider providing context at the end of the session, reminding participants of what the core aims of Shinrin Yoku generally are, so as to mitigate any long-term misconceptions.