Answer: The best thing you can do to improve your soil is to add organic matter such as compost. Compost is partially decomposed organic matter and is the most organic of the organics. I consider it my number one, best soil amendment. It can be purchased or made in your own backyard out of old plant matter.
Mixing compost in with the backfill soil, when planting, benefits the plant by creating food for microorganisms that will continue to decompose the organic material. Decomposition produces nutrients for the plant and also creates acid, which will offset the soil alkalinity. Compost also changes the structure of the soil, making it more permeable to air and water. Since most nursery plants come in potting soil, mixing compost with the native soil will create a transitional area for the plant's roots.
Compost can also be spread around the plant on the surface periodically over the long term. It will help prevent the growth of weeds and will make weed pulling easier, if any do pop up. It will also facilitate decomposition on the surface helping to enrich the soil. Generally, an inch or two of compost on the surface is usually sufficient, and it should be allowed to decompose and thin out before the next application. By digging in the old compost and adding fresh new compost each year, you will improve your soil over the years, ending up with wonderful garden loam and healthy plants. Best wishes with your garden!
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