When can you plant them on Long Island?
Plant outdoors after danger of frost has passed.
Can the primroses that you can purchase at grocery stores and flower shops be planted outside?
Most primrose varieties can grow outdoors in gardening zones 4 to 8, so if you live in one of those zones, then you can plant them outside. Also, see this article to ensure you have an appropriate spot for them in your garden:
https://www.gardeningknowhow.com/ornamental/flowers/primrose/growing-primrose-primrose-plants-in-your-garden.htm
I have heard these are very toxic to dogs and can be fatal if eaten.
Primrose is listed as a toxic plant for dogs by the ASPCA:
https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/primrose
Other sources say that the toxicity is usually mild. However, each animal reacts differently, so it's best to be careful.
I planted primroses in tubs last year. They didn't bloom. This year they have come back looking healthy with an abundance of foliage - but no blooms!!! I have been feeding them with Tomato plant feed every week - is this promoting the foliage but not the blooms? Advice greatly appreciated. Thank you
You may be feeding them too much nitrogen; which will give you lots of green leaves and inhibit flowering.
We recommend a light feeding of organic compost.
You could do a soil test to determine what the soil contents is.
Bone Meal can up your phosphorous levels and promote flowering.
Here are some links with more information.
https://www.gardeningknowhow.com/ornamental/flowers/primrose/growing-primrose-primrose-plants-in-your-garden.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/fertilizer-numbers-npk.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/bone-meal-fertilizer.htm
Will the plant die if exposed to direct sunlight all day? I have them in my garden which is part shade and part sun, I have tried to plant them around my front light post which is sun all day but they die after about a month. I have tried doing this for the last two years with no success. I use the very best potting soil. I even removed all the soil and replaced it with fresh soil but they still died after a couple of months.
Full sun would not be a good location. A dappled sunlit area of a garden is best.
Here is a link with more information: https://www.gardeningknowhow.com/ornamental/flowers/primrose/growing-primrose-primrose-plants-in-your-garden.htm
Could you please tell me what I should do after my primula vivali has finished flowering. I wondered if I should cut the stem to the bottom of the plant or leave it to wither away
Primula vialii (I like your vivaldi) blooms can be cut to the ground. However, it is a short-lived plant so some self-sowing is desirable.
Hello, My primroses are doing beautifully except they grow more leaves than flowers! The plants are very healthy and it seems a shame to cut the new strong leaves back to allow the flowers to come out. I have to continually move leaves aside to allow the flowers to show their lovely faces :) What am I doing wrong or what should I do be doing? Thanks Janet
Try dividing the plants this fall. They may simply be crowded. Also, avoid using fertilizer. A layer of compost at their bases should be all they need.