Where I live in New Mexico, the soil is more alkaline than acidic. That means I might as well forget ever trying to grow blueberries, but asparagus is a great choice. We even found some old or wild stalks along our ditch bank last year.
And a soil’s pH balance is just one consideration. Soil texture and drainage are especially important to a plant’s success in a vegetable, herb or ornamental garden. If we didn’t add some organic matter to our vegetable garden each year, the soil would compact from foot traffic and lose nutrients from its work feeding plants. So each year, we work the soil with mushroom compost to keep it rich, water absorbent and well draining.
I couldn’t – and wouldn’t – rework my ornamental garden soil each year. For one, it would be nuts to dig up perennial plants! So gardeners often are advised to add a little bit of compost to the hole dug for a new tree, bush or flowering plant. The compost enriches the soil around the roots, and as long as you water as suggested in the first year or so of more rapid growth and root set, the plant should thrive. But what happens as the plant grows beyond your amendment, especially if you put in a rapidly growing shrub or tree? Eventually, the roots work their way into the soil you haven’t amended. If the soil is so poor or compacted that the roots can’t break through or thrive, the plant could be stressed at the least.
If you choose a native plant, especially for a xeric garden, it’s likely that you won’t have to amend the soil at all. A plant that is adapted to your area’s typical soil makeup will do better if you just loosen the soil around it, usually to an area at least three times larger than the root ball. No need to add anything.
If plant instructions, or one article or expert tell you to add to the soil, it helps to verify the information with another source. That’s especially true if installing a native plant in your xeric garden. And it’s even truer depending on the first source of advice. There are plenty of reputable sources, and then there are myths, many of which can be perpetuated by those who stand to profit.
It’s also good to check local sources when amending soil. For example, you might hear that adding sand improves drainage, but if you add too little sand, or add sand to clay soil, you can make matters worse, and your soil sets up like concrete. Oh, those poor plant roots…
Most organic matter is good for soil, but plenty of myths abound there as well. For example, manure needs to cook down or compost with brown materials before throwing it on your vegetables. Wood ash is often touted as an amendment, but not in New Mexico, where the soil already is alkaline. Wood ashes also are high in salt. I talked about Epsom salts in a previous post. The bottom line? Get local advice from a few good sources, and if you go with native xeric selections, you probably won’t have to amend the soil unless you have a severely compacted or poorly draining area.