I second ycmahesh's opinion on weed mat and on stone mulch - bark is a much better alternative. Just keep all mulch away from the crowns of the plants to avoid rotting them. A soil test is always a good investment. This is a case of "do as I say, not as I do", though, as lots of gardeners skip this step - I know I have not had as many soil tests done as I should have had. You did not mention which direction this bed faces - is it to the north, south, east, or west of your house? Is it in full sun, part sun, mostly shade? Are there gutters on your house, and what kind of roof overhang do you have - is part of this bed under an overhang? Please reconsider the depth of the bed - 20 x 4 is too narrow and may look surprisingly skimpy. If you can get close to a 1 to 3 ratio, and at least 6 feet deep, it will be much better looking and will allow you more flexibility to have a variety of plant sizes. The 3' closest to the house may be *very* dry, and you need to leave some space for access to the side of the house for various tasks like painting, residing, window glazing ... these activities wreak havoc on a garden, and contractors (or relatives) will not understand that they're breaking your heart when they tromp on the soil. Instead of plastic weed barrier, you can use newspaper under bark mulch; you can fold it up so pieces fit between newly planted perennials; when the time comes to move things around the paper will have decomposed. The newspaper will last long enough to smother the bits of grass that are trying to re-sprout, if you make them about 3 pieces thick. Since you don't have time for a lasagna bed, you may want to remove the sod with a flat spade and put it into a compost bin for later use. This works better than tilling it into the soil, because the clumps will resprout at an alarming rate. The depth to which you need to till will vary - here we sometimes have hardpan under the soil, sometimes not. If you run into fast-draining sand under your soil, you can leave it alone. I sometimes dig down about 2' but only if I'm including plants like peonies (which will be there for decades) or if I'm using plants that need really good drainage. This is about the maximum ever needed for perennials, I think, and you can easily get away with half that, maybe less. But! ... you get only one chance to start a new bed, so make the most of it. I don't use purchased top soil in beds, as it tends to be of uneven quality and full of weed seeds. I mix in lots of organic amendments with the local soil - aged manure, compost, leaf mould, coffee grounds, whatever I can get. Peat moss can be a problem, and you might want to research that before you use it. Keep us posted, please; this sounds like a fun project.

You can grow most all annual flowers with the right soil mix. Keep in mind that some plants just don't like our salty soils, salty water, high heat and low humidity. Most of us have used the 'trial and error' method to find the varieties that survive in our planting areas. 1) Your goal is to create a bed that is about 12 inches deep. First, moisten the area well by letting a garden hose trickle for several hours or overnight. Wait 4 - 5 days before digging. You'll want soil that is moist but doesn't stick to your shovel. A great recipe for garden soil is 1/3 native soil, 1/3 compost or composted mulch and 1/3 pumice, coarse sand or perlite/vermiculite. Our clay soils hold moisture but tend to be 'tight' and can restrict water and air - hence the compost and sand/pumice. 2) Till the area with a shovel or garden fork - or you may want to use a rototiller. Add a 4 inch layer of compost/mulch and 4 inches of sand/pumice. Till again. This will give you your 12 inch garden depth. 3) You can add amendments like ammonium phosphate or ammonium sulfate before you till. 4) When you are done tilling, the garden bed area will be higher than the surrounding soil so you may want to use a border of some kind. There are dozens of choices from the standard concrete blocks to more decorative stones, wood or even PVC. 5) To water your beds I'd recommend the 1/4 inch tubing that has emitters built in. Each emitter puts out 1/2 gallon of water per hour and they are spaced either every 6 inches or 12 inches depending on the brand. I'd discourage the use of microsprays because much is lost to evaporation. I'm sure others in the forum will have more ideas for you. Here's a link to a guide on what to plant and when. Good luck. Here is a link that might be useful: Flower planting guide

I have the same clay crud you have. It takes about four or five years from starting to amend an untouched bed to getting workable soil, and it's always going to be a "heavy" soil, so you're not going to have a whole lot of success with things like blueberries, lilies, salvias or certain lavender species, all of which require sandy soil. If you absolutely must have these plants and don't want containers, you can always play gravedigger for a day and dig out everything to five or six feet deep and replace it all with topsoil, but that's not the most practical of solutions - and I do speak from experience! Here's what we did to deal with the clay: Year 1: Rototill beds and dig out any offending plant roots (you'd be surprised how much of this you'll have to do, especially if you have lots of trees or shrubs). Till in several bags of Clay Buster (a soil amendment you can get at most garden centers) and/or peat moss or pulverized pine bark (clay is also highly alkaline - ours tested out at pH 8.0 in places!) Add a 2" layer of composted manure on top of that and tamp down; mulch after planting. In fall, remove or till in dead plants and mulch. Add as many fallen leaves as you can rake up to beds. Year 2: Your bed should be double-diggable by this point, so you can avoid the Rototiller. Add several more bags of peat moss or pulverized pine bark (both are good soil looseners) and dig that in. Add more compost on top of that. Plant, mulch, add leaves and dig under in fall. Year 3: You'll probably want to pH test your soil before adding anything more acidic (unless you absolutely must have blue hydrangeas or other acid lovers). Otherwise, same procedure as the first and second years. Year 4: Don't do a lot of spring digging in this year unless you have to, as you're looking to build soil structure now. Just add a thick layer of compost to the top and tamp it down. Plant, mulch, dig under in fall. Year 5: Done! You'll want to add compost or your choice of organic matter yearly to maintain the beds, and of course, mulch is your friend! Hope this helps!

I don't think spot treating is going to give one an attractive wildflower meadow. Its going to look clumpy - IMPO. And most bulbs are not native, not sure if that is important to your planting or not. Round up is not as safe as claimed above. IT can hurt animals, particularly fish and amphibians, when not used correctly. I do think roundup is safer than most other herbicide alternatives, but it needs to be used wisely and in accordance with directions. If you are starting with lawn, I would either smother it with newspapers and mulch and plant the area in plugs. Or I would kill the area with round up, wait a few weeks, mow the dead turf off and then overseed the area with a quality wildflower mixture, right into the dead turf. You can get quality seed mixtures from places like Prairie Nursery, Prairie Moon Nursery and Ion Exchange. Those are US sources, you may be able to find a Canadian equivalent. The Prairie Nursery website contains some good instructions on how to prepare a site. I would suggest you read that also.