|I recently purchased a plant with both yellow and deep purple flowers. The yellow is an allamanda & (thanks to you) I realize now that the purple is a penstemon. Is it a good idea to keep these plants in the same container or should I separate them? I'll bring them in the house when it gets cold.|
|Your allamanda is native to Brazil so it won't do well outdoors during your cold winters. The plant will appreciate being grown inside. Begin by taking it indoors at night when nighttime temperatures are about 50F, and then taking it back outdoors for a few hours each day, eventually keeping it indoors 24 hours a day. This will lessen the shock of being indoors.
The penstemon is probably just a hitchhiker. These two plants are rarely planted together in a container; I wonder if it is a volunteer and the garden staff thought it made an attractive combination? In any event, I'd remove it and pot it up on it's own. Penstemon can be persistent in the garden and somewhat invasive if left unattended so you might want to keep it in a container rather than plant it in your garden.
Best wishes with your garden!