Question
QUESTION: Hi,
Unfortunately, I have soil that is mostly "fill" and not "topsoil" in my backyard. It is mostly clay, with lots of rocks (small and large). I have tried amending my soil by tilling the clay soil and then adding about 3 inches of good topsoil and 3 inches of compost and mixing it all together. When planting my plants I added a commercial fertilizer to the holes I dug, sometimes substituting bone meal when I knew that was what the plant liked and sometimes adding "Holly-tone" for my acid-loving plants (when I had the soil testing, it was amazingly "neutral"). However, my new plants don't seem to be thriving as they should and the soil seems to still be mostly clay.
My question is: how much is too much? I was tempted to add bone meal AND the commercial fertilizer to each hole I dug and now I'm tempted to top dress the whole thing with some manure. What I'd love to end up with is dark, rich-looking soil instead of the reddish clay stuff that I see. Will that ever happen? Will there be a visual difference when I get it right? Also, going forward to next year, will topdressing my soil with the amendments be enough or should I till around the plants as much as I can? What do you think of a compost/bone meal/manure/peat moss combination as a top dressing, next year?

ANSWER: Hi Leslie, Fortunately you have clay!  Clay is good!  It's what you want to start with for most plants.  However, clay particles are very small and they pack tightly which slows drainage and root development.  Picture a grain of sand the size of the White House.  A clay particle would be the size of an orange.
With clay soil you should dig wide, not deep holes. Never any deeper than the container and usually not as deep.  The root ball should be elevated slightly above your soil level, higher for plants that need better drainage like azaleas.  Dig the hole 2-3 times as wide as the root ball and amend, not replace, the soil.  
Most container grown plants are in a pine bark based growing mix.  The ideal transition area between your clay and the bark mix is a blend of both.  The clay holds moisture and nutrients well, the bark creates air spaces and provides pathways for the roots.
Finely ground pine bark, coarse leaf mold or cotton burr compost all make excellent amendments for soil.  A little manure, compost, organic peat and/or sand added to it is ok also, just don't over improve your soil.  You still have a clay bowl that fills with water if the soil mix is too loose.
A little fertilizer blended with your soil at planting is fine.  Organic (or mostly organic) products like Holly-tone can't burn so they are a good choice to incorporate at planting.  Synthetic fertilizers usually yield quicker results but can burn if used improperly.
I use both.  Bone meal is a good source of phosphorous but if you are using a good quality, well balanced plant food, you don't need to add bone meal.  Follow the label instructions when all else fails.
Avoid top dressing with the products you mentioned.  These break down in time forming a layer of very fine particles that slows air movement and covers feeder roots that are at the surface because that's where they need to be.
A coarse mulch added helps retain moisture, moderates temperature changes, allows air flow, suppresses weed growth and looks nice, but when you think you need more, rake everything out back down to soil.  Save the stuff you remove to add as a soil amendment and then replace the coarse mulch.
Perennial beds may need to be reworked every few years.  As the soil breaks down, the soil drains more slowly, so plants that need excellent drainage may suffer.
Usually our plants suffer because we pick a plant because of it's appearance, not according to it's needs. Many plants grow well in poor clay soil, they just aren't as exciting or as spectacular.  Jim

---------- FOLLOW-UP ----------

QUESTION: Thanks for the quick response! As a follow-up, your response begs me to ask,"What is the difference between a good quality, well balanced plant FOOD and a good quality, well-balanced FERTILIZER?" Do they serve different purposes and can you recommend a good "food"?
Thanks again for you timely, expert advice!
Leslie

Answer
Same thing.  The term "food" is excepted better by organic gardeners than "fertilizer".  Espoma (Holly-tone) makes a good product.  Plant-tone and their lawn food is 100% organic, the rest of the tone products are close.
If you're not opposed to synthetic fertilizers, Ferti-lome makes a good quality product, so does Sta-Green.
For container plants, I like fish emulsion - sea weed blends and I like Schultz products. Jim