Hi - I am familiar with impatiens, needing shade and lots of water, but have never had forget me nots (dwarf, Victoria blue). I saw them at the nursery and couldn't resist. I know they are perennials and like shade. Will they do well together? Also, will one be enough or should I put more? Thinking I'd put the FMN in the center, I bought three and would like to put one in a hanging basket also. Do they do well in hanging baskets?
Suppose I could just try but thought I'd ask some experts.
Forget me nots are pretty tolerant of a wide range of conditions, and should grow pretty well with Impatiens, as long as they are not in a really dark shade area. If you are planting them in a large container I would place them all around the edge, perhaps 6" apart, Impatiens in the interior, 6" to 12" apart, depending on variety.
The FMN will sort of hang over, not a lot.
They will reseed, new plants growing in almost every little niche of soil where there is even a little bit of water. They are a really nice ground cover in a bright forest floor sort of setting, and make a good cover over bulbs.
They are not long lived, though they might survive longer in a mild climate. Our summer heat seems to kill them off pretty fast. They do OK if they are in a cooler, shaded garden here.
Assuming you're talking about Myosotis? If so, agreed they don't make it through the heat of summer here, but that may not be a worry in WA state. As a stalk of flowers finishes, if you cut it off, the plants will be inspired to make more. I might add some Lobelia to the planters, just to make sure there's something to complement the Impatiens as summer wears on. After a couple months, Impatiens should be much taller and fuller than Myosotis. They might completely engulf the Myosotis. Lobelia would run over the sides to find some light.
However, about Impatiens, there's a disease called downy mildew (not powdery mildew) that's causing issues for Impatiens in some areas. It's spread by wind (or contact with infected plants) and kills the plants. For this reason, I've been going with wax Begonias instead of the Impatiens this year. Chances are your Impatiens will be fine, but there are a few things easy things that can help. Try to water the soil only, not the foliage. When you're at stores that sell plants, don't touch the Impatiens unless it's because you're buying some, especially if they look like they're not in perfect health. Wash your hands when you get home before you touch the plants you already had.