Two questions have come to me in emails recently (and how would I know what to write about without your questions?)

They are kind of related. 

Is there a way start, stop, and join  sashiko threads without making a knot?

and

How to keep the back of your sashiko stitching looking nice when stitching small design elements like the centres of flowers.

For years I used the method for starting and ending threads that you'll see in my sashiko tutorials. It simply passes the end of the thread under a few stitches  on the back. It is flat (unlike knots) and stays put. It has worked well for me because I usually use my stitched sashiko pieces in sewing projects where the back is not visible.

But if you want the back of your stitching to look as close as possible to the front here is a method that looks the same on both sides. It involves taking some tiny stitches under existing stitches. 

Starting a thread.

Begin four or five stitches in, and stitch back to the beginning as shown here

Then turn the fabric over and make tiny stitches as shown below. You only need to catch a few threads of the fabric in each stitch. Try to stay directly under the existing stitch on the front of the fabric.

Pull your need through and then continue to stitch along your design on the right side of the fabric until your thread runs short.  

Below is the back with your stitching started without a knot. The needle is pointing at it :-). You can also see the back of another line of stitching started in the same way  in the white stitch line.

Below is how to end this thread and begin your next thread. I'm using a white thread to make it easier to see what I'm doing. 

For now, leave the end of the thread that you are finished on the back of the fabric. 

On the back of the fabric take tiny stitches between the stitches, taking only a few threads of the fabric and keeping this new thread under the yellow thread on the front.

Pull the new thread through. (Stop pulling when the end of the new thread is more or less at the point you began stitching.) 

Front:

In the above photo you can see how the new white thread is underneath the yellow thread and doesn't show. Below is the back of the stitching. Again you can see how the join is nearly undetectable. 

In the example done with all white thread below you can see the start and the join more clearly. This is because I took bigger stitches on the back- 2 or 3 threads of the fabric would have been enough and have showed less.

The photo below shows how ending your last thread in a project is done in much the same way. On the back stitch several tiny stitches under your last few stitches.

Finally, clip all the tails of the threads close to the last stitch where they end. 

Front

Back

As for those pesky cherry blossom centres? I don't know of a way to make them look the same on both sides. I don't think it is possible, just be as tidy as you can.

Or, it occurs to me that if you are stitching through more than one layer of fabric you can bury the carried threads between the layers.

Many  traditional sashiko designs have continuous lines and can be stitched so that both sides look the same (no need to carry threads on the back on these).  Choosing these when you sashiko stitch would make it possible to get bragging rights for the back of your stitching! 

Enjoy your stitching!

Susan