Question
Hi
I have clay soil and want to plant/ plan perennial garden beds

most imporant atm is my front yard
I currently have in my front garden the following newbie plants
2 hostas
1 Lavendar
1 Mum-red
2 asters
2 mini rose bushes ( want to move to the backyard)
10 tiger lillies in one corner
What plants best grow in the soil i have?

I have as i plant removed the clay and planted with triple mix instead - i also will put petemoss over for the winter

I know this is a mess of an email - i am still learning to garden

tks carol

Answer
The first thing I want to tell you is that Hosta's need to be in the shade, or shaded from the afternoon sun, or they will get burnt. So either in a east or north exposure site.  Lavender, Mums, asters, and rose bushes, need Full sun, which means a Southern or western exposure site.  And Tiger lilies can either be in Full sun or part sun (east, west, or south exposure). Secondly, make sure you are paying attention to the plant heights at maturity and plant the taller one's in the back, medium one's in the middle, and short one's in the front of the flower bed.  So that they don't get too tall and block out the sunlight to the other one's behind them etc.  

Perennials can pretty much grow in any type of soil, once they get established. But when you go to plant them you should amend the soil by digging the soil twice a wide as the pot they come in and with the soil you remove from the ground you should mix in compost or potting soil, to add nutrients and lighten up the soil. Which it sounds like you are doing.   This is so the new delicate feeder roots that develop have a nice light and fluffy mixture to go into.  By the time the roots reach the hard clay soil, they are strong and can push through it.  

It is also good to top dress your soil every year with a couple of inches of compost (black organic rich soil) to help keep your soil rich in organic nutrients.  And try to work it into as best you can considering how hard your soil is.  But it is really beneficial to work your soil every year.

It sound like you are doing good by adding the triple mix, but you don't necessarily need to add peat moss, because that mostly used for water retention and clay soil  retains a lot of moisture already.  You need to lighten up your soil and make it not so heavy on the plants, and make it drain better.  So you should add sand, or perlite to your soil to help it become lighter and make it drain better, and you can do that at the time you plant.  

Also you should use a slow release granular fertilizer Osmocote at the time you plant and every season there after.  It slowly releases beneficial nutrients when you water.  

Another important thing to know is to deep soak your plants during the hot part of the season June-September.  And do that a couple times a weak.  Do not just rely on sprinklers to do the watering for you, because they don't provide a soaking to the root system, only the first few inches of soil get watered. And drip lines and soaker hoses, would definitely over water your clay soil and root rot the plants to death.  So you should let the first two inches of the soil to dry out in between waterings and then provide a good deep soaking.  

Dead-head your perennials by removing the dead bloom heads after they are done flowering. you can also prune things that get long and lengthy  by gathering it like hair in a pony tail and cutting straight across, creates a nice uniform shape.  

Your lavender & rose bushes will get shrub like and woody, so don't ever cut them all the way back to the ground, even for the winter, or it will kill it.  You can prune the roses and lavender in the spring, to shape by only taking a few inches down to health buds that are beginning to emerge.  

Your mums and asters should only be cut back to 6-8 " after they are dormant, in the beginning of winter.  

Your hosta's & lilies can be cut back 2-3" after they are dormant in the Fall.

Side note:  To get your mums & asters to stay short and bushy and bloom in late summer or early Fall, you need to keep pruning them back to lateral branches until July 15th and let them go after that point and fertilize them then too, not earlier in the season with the rest of your perennials.  

I am sorry, I know this is a lot of info, but these are all the basic things I say to the customers I have, about general gardening tips and perennial care.  I hope you find this info helpful and let me know if you have any other questions.  I specialize in shade gardens, roses, greenhouses, and all other perennial gardening and care.  I have extensive landscape knowledge, etc.  And I will be her to help you with anything else you might need.