Rruuunnn, thanks for the compliment. You make me blush!
I try and share all the info I either know or can research. I have never grown wedelias so all my info is from what I've researched and know about certain types of plants in general. I don't remember where you live, but I'm thinking it was a warm zone, perhaps California and zone 9? Anyway, I'll still try and help you.
Some good advice from Kale. Junipers want full sun of 6 hours or more, so they won't do well in a shady spot.
I forgot to mention that I put mulch over the periwinkles. will the mulch hamper spreading?
If the mulch is covering the plant or pressing against the stems where they come out of the ground, it can cause them to rot or smother them. The mulch should be under the stem aka vine of the plant, and just up to the stems where they come out of the ground. Here's some pics. In this first one the periwinkle has grown through the mulch and sits on top of the mulch.
Here's newly planted and mulched vinca - aka periwinkle.
It will take about a year or two to fill in. As for the bees, they will be attracted to it but bees tend to be too busy to bother people unless they are stepped on or otherwise harassed. I would think the wedelias would attract bees too. Flowers that are tightly doubled blooms are less attractive to bees as they can't easily get to the pollen. Here's a mum that has petals covering the pollen.
This one has the pollen exposed and easy to get to.
Without knowing your hardiness zone it's difficult to make recommendations, but you might want to consider plants with colorful leaves instead of flowers if you don't want to attract bees. Caladiums grow in shade and come to mind but they are only hardy in zone 10 and warmer, so you would need to lift the corms for the winter and replant in spring.
Croton is another plant with colorful leaves that can grow well in shade but is also tropical in nature.
If you add your hardiness zone and state to your location in your profile it would be most helpful.
the home depot guy told me to use pot soil, why, I don't know.
Maybe he said that because he thought you were planting in containers and the potting soil allows for better drainage.
fox nursery told me not to use compost but to use fertilizer, probably to make more money. anyways, this is where I'm at.
I don't think so as you would probably spend more for the quantity of compost. Again, I'm not all that familiar with wedelia and the sites I gave you should help with what type of soil they prefer. If the fertilizer was recommended for the periwinkle then I would suggest you use an organic fertilizer. If you are planting under a tree, anything you add to the soil will effect the tree. Compost and organic fertilizers are gentle in the way nutrients are relaeased so it's great where ever you use it. Synthetic fertilizers will cause a flush of growth that tends to attract insect pests and can leave behind residual salts over time and that's not good for trees.
the home depot guy told me to water the garden a half hour every other day to help the roots grow. is this correct?
Without knowing your weather it sounds a bit too often, but do be careful with overwatering your tree. Water when the top inch or two of soil dries until the plants are established. Just stick your finger into the soil under the mulch. Up to your first knuckle would be 1" and the second knuckle would be 2".
I hope that helps,