Question
I planted 2 hostas under my dogwood tree last spring/early summer.  They seemed to be doing fine at the end of the fall.  One even grew a flower.  I also planted 3 more hosta bulbs, silver lamium, and lilly of the valley under the same tree last fall.  None of these are coming up, even though my mother's hostas have already sprouted.  She lives 2 doors up from me.  I put gardening cloth down, through which I cut holes to plant the bulbs and plants.  I mulched over that.  What might I have done wrong?

Answer
You may not have done anything wrong. Micro climates can make a world of difference. By that I mean, one spot which receives even marginally more sun than another spot can differ in 4-6 weeks with respect to spring growth.

Hostas planted in the ground for years typically develop larger root systems with more carbohydrate reserves which aid in the early spring recovery as opposed to small hosta plants which still need to establish themselves. Early April is still very early in most parts of the country (I am not sure where you are located). If no sprouts by may/june I would start to be concerned.

Some newly planted perennials may not come back at all. that is just the risk of transplanting perennials. Typcially, the amount of soil preparation, care (especially water) they got the first year will determine this. One year we planted 20 hostas but watering got away from us and by summers end the plants shrivled up and died. The year after we watered newly planted hostas  twice per week through late fall and they all came up the following year.

It all depends..

In any event, it may be too early to say conclusively what happened.. even if anything happended. Local micro climates can make a world of difference, but in general, the more baby care you give newly planted perennials, the better result you will get the following year. Watering deeply twice per week until the plants die back in late fall is usually the best care you can give them. If you have to plant new plants this year, mix in plenty of compost or other organic matter into the soil. this is the best care available for shade loving plants.

(remember moisture under large mature trees is often less readily available due to tree canopies shielding rain and competition from the tree roots).

I hope I was able to help.