I wasn't aiming for botanically accurate imitation flowers. What I had in mind was something that looked obviously knitted, just something whimsical to show off the texture and colour of the knitting.
For the stems I made some knitted i-cords and reinforced them with green paper-covered wire. I've seen a similar thing done using plastic drinking straws, but I wasn't keen on the idea of straws, and I thought pipe cleaners might be too bendy. The ends of the wire are bent over and hidden under the flower centres, so there's nothing sharp to catch on anything. Each poppy is about 2.25 inches across. Not too big and not too small.
The yarn is Baby Cashmerino by Debbie Bliss. I think this is my new favourite yarn. It's a bit finer than standard dk weight and comes in a wide range of beautifully flat colours. This is a peek from my stash and shows just some of the colours.