I think you just need to have a little more patience with them. They'll turn.

I think they've had long enough to be mature. Why don't you pull one off and peel off the outer layer to see how the seeds look? If they are hard (can't be squashed) and shiny, you're good to go. Generally, they are mature enough after six months even if the color hasn't changed. I've opened green berries like that and found one or more seeds that have already sprouted.

Hi Ddruck,

I've also experienced my berries staying green for well over a year. I don't think it is necessary for them to turn red, as long as they have had enough time to mature, as Ohiofem stated. I would definitely try peeling, cleaning and preparing one of the berries and try germinating the seed. I've been growing clivias from seed now for over 10 years and I have some plants that take over a year before they turn red or yellow.

I was just speaking to someone last night who told me she took a red berry and put in in the fridge for a week or so and just stuck it in some potting soil watered and it is starting to grow. It will not happen overnight but it took. I have sprouted seeds by peeling outer layer and sanitizing seeds, however this seems much easier. I have one that bloomed this spring and will give it a try. Best wishes in your endeavors. Let me know if it works for you.