What is a seed rhythm?
 You are in a drum circle with some beginners and some people with experience. A Drum Circle is all about improvising but sometimes it needs some input to get the ideas flowing. With complete beginners even the idea of putting in a beat becomes a seed rhythm. So a seed rhythm is something to work with, to get things started.

How do you plant the seed?
You can plant openly or sneakily or use my favourite method which is to steal a participants seed and plant that.
    1.    Openly: You tell everyone you are going to plant a seed and watch it grow. As an example you might start with the beat. " I am going to start playing the beat, you can either play the beat with me or play something else that fits with the beat. Look around and see what other people are doing and steal their ideas. Lets see what happens." I would then start playing or clapping the beat until I felt it was established and then I would do as I suggested and steal someones idea.
    2.    Sneakily: This can be done when a circle is in full flow but things feel a bit stuck or some participants seem to be lost. You simply start playing something simple strongly and watch it catch on. Once its caught on you might go to a different part of the circle and plant a different seed.
    3.   Stealing seeds: The circle is in full flow but you feel a more focused rhythm would help things along. So you look around for someone who is playing a simple rhythm consistently with confidence. You then stand or sit near them and start copying their rhythm quite strongly. Usually it will catch on quite quickly and you can move off and steal another one.

How do you help it grow?
If you are working with a very  obedient cooperative group it can easily happen that you plant the seed and nothing grows from it. They just copy exactly what you did and stick with it. There are a few strategies for working with this.
    1.   Plant lots of varieties: Using the beat as an example you could give the bass drums a slow beat, double that for the hand drums and double it  again for the shakers. With a more complex rhythm seed you could give a simple version to bass and add different twiddly bits for hand drums.
   2.   Don't give them time to learn it:  Sometimes I will just play a rhythm once for a group, that way they automatically come up with their own variations. The longer you take demonstrating a rhythm the more likely they are to try to copy you precisely.
    3.   Use an odd instrument:  If you play a rhythm to a group of hand drummers on a hand drum they are going to try to do it just like you. Use a cowbell instead or claps and clicks or mime it in the air. That way their response will always be an interpretation rather than a copy.
    4   Stop and start again: If everyone is intent on being very accurate and not really adding anything to the ideas then STOP. Acknowledge how brilliant they are at performing that set of rhythms and then invite them to add some ideas of their own 1-2-0ff we-go

What can get in the way of growth?
Mostly groups are very happy to make up their own things and success is mainly down to the attitude of the facilitator.  If you are worried that they won't be creative ...guess what shows up.  If you think they need to be taught a rhythm before they can come up with ideas of their own ...guess what shows up. If you think you will have to play along all the time just to keep them steady... guess what shows up.
I was working with a group of teachers learning to facilitate and a question was asked from a space of "I am worried that I won't be able to keep them going." I asked others to comment on what I had just done to keep everyone on track. Someone raised their hand and said. "You counted to four and got us playing, then went over to that table and made a cup of tea and ate a biscuit."
The more you can empower the group to keep things going the easier it will be for you. The more you try to keep control the less empowered the participants will be.