Research has actually shown for a long time that amending planting holes is extremely counterproductive, especially for larger plants (as opposed to small annuals), but that knowledge has been slow to infiltrate the public consciousness. Why is it so bad? 1) Roots are already very "reluctant" to venture out into soil that is inhospitable compared to the potting mix it was grown in. Amending a planting hole essentially creates a container in the ground, causing the roots to circle, become bound, or even strangle the stem. 2) Most plants have significant ability to adapt to the native soil, but will not do so unless "forced" to. Hence planting holes should be back filled with native soil to jumpstart this process. 3) Planting holes that are amended with large amounts of organic or coarse matter create a "sink effect", especially when the surrounding soil is finer and less permeable. When water is plentiful, this can create anoxic conditions at the barrier between the soil types. When water is scarce, highly retentive native soil will not readily release water to coarser organic materials, and can make the planting hole hydrophobic. When amending native soil, more and more research is suggesting that attempting to plow in amendments more than very superficially is counterproductive and very harmful to the "soil food web". In fact, the much more convenient method of simply topdressing, minimally incorporating, or simply mulching with organic matter (or making it the main component of a raised bed mix) is much more effective in increasing percolation and thus improving drainage, along with a host of other benefits. Some aspects of this concept are referred to as "no till" by proponents. For example, if you tried to use gritty mix directly in a planting hole, you'd essentially create a dry well... a situation very few plants could survive. PS, you can find a lot more information about this on other forums, this being one for container gardening :P

I don't see a problem with it. The only potential problem with top soil is that it is an incredibly generic term and can mean anything. It might be soil very suitable for growing things and it might be garbage. The top soil will also almost certainly have a lot of weed seeds in it, just the nature of the beast. However, in a 15" bed it really doesn't matter. Do as you were planning and place it on the bottom as filler. Even if it were the worst soil on earth, 6" of it would still give you 9" of great growing area which is enough for just about anything. If it does have a lot of weed seeds they would be buried deep enough they would be unlikely to ever emerge. If the top soil appears to have some clay in it it will be a water and nutrient sponge. If this is the case you may want to mix it right into the mix for this added benefit. Then again you live in Seattle so I don't know that water retention is all that important to you. Anyway, my point is you aren't going to hurt yourself if you use it to appease your family. I suppose I do wonder why your family would be so controlling as to not let you just 'try something new', but that's really none of my business.

I'm sorry jtcm but it wasn't my intent to offer that link as some sort of definitive authority, just a source of additional info on the question. There are multiple other sources available online that you can Google if interested. I just thought you were looking for general info. While we're at it...let's re-use our trays without cleaning them and keep the seedlings covered until the true leaves emerge. I don't see how that follows. There is a great deal of difference between adding small amounts of well-cooked compost to a mix and intentionally using dirty trays/containers or keeping seedlings covered. As I said above, I'm far from the only person who uses compost in their seed starting mix. A search here will pull up many discussions about it. And if you believe your seed starting mix is actually "sterile", in the usual sense of the word, then you are misled. Most all packaged seed starting mixes, including ProMix and Metro Mix not to mention all the Scotts products add composted ingredients in various forms to their mix. All the organic seed germination mixes on the market include compost in some form. ProMix even advertises the addition of mycorrhizal fungi to their mix as one of their selling points. And then those bags get transported all packed together inside a hot truck to the Home Depot or Lowe's or Walmart outside store yard to lay around in the sun and the rain until someone buys them. Meanwhile the composting process started in the factory by mixing those ingredients goes on in the bag. Feel free to do some additional research on the issue yourself if interested or, if you prefer, just don't use it. The seeds will germinate either way. ;) Dave

Hi, AR. Thanks for the kind words. I don't get snippy about what people use for a soil because I don't care beyond the fact that I'd like everyone to get all they can from their growing experience. I do care when, during the course of a conversation, misleading or erroneous information that has the potential to limit your experience is claimed or inferred to be true. I'll argue those points with gusto, for no reason other than the fact I think it's important for (the collective) you to have accurate info if you're to make good decisions. I think it can safely be said that the number of plants that would do well in soils in which they naturally occur would be somewhere between very few to practically none, with the overwhelming number of them crowding each other for space at the 'practically none' end of the comparative scale. Putting mineral soils in a pot changes the way water physically behaves in them due to the fact it eliminates the wicking effect of soils deeper than pots. I said all that to say it hardly matters a whit, what type of soil the plant prefers growing in situ, 'cause it ain't gonna like it in a pot. Also, I don't think you should be thinking about trying to use the fines left over from screening Turface as a significant fraction of a soil for plants that happen to be vulnerable to ill effects caused by wet feet. You can increase water retention w/o introducing a perched water table by screening the ingredients to a size large enough to ensure the medium can't hold perched water, but also increasing the volume of ingredients that hold water INSIDE of the soil particles. IOW, screened ingredients equaling 4 parts Turface 3 parts bark 2 parts grit will hold a lot more water than the standard 1:1:1 screened parts by volume w/o sacrificing any notable amount of aeration or drainage, and it won't invite a perched water table to take up residence in the lower reaches of the pot. Al