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8:10 PM Thu, Nov. 15th

Garden column: National advice doesn't work with Arizona soils

Courtesy photo<p>
Regional soil ph levels differ greatly, so helpful gardening advice for one area may be harmful in another climate.

Courtesy photo<p> Regional soil ph levels differ greatly, so helpful gardening advice for one area may be harmful in another climate.

National-brand garden products drive me crazy. I've tried for years to get these companies to market a product appropriate for use in the mountains of Arizona, but to no avail. At the time I contacted one company about this issue, I was its largest product dealer in the state and felt that I had considerable clout behind my request. But, unable to get a response to our unique mountain challenges, I stopped carrying that company's products in my store. I now deal with Ferti-lome. It's a small Texas-based company that understands our Southwest gardening needs.

Unlike the acidic soils of East Coast gardens, our soil is alkaline. The result of alkaline water that eventually transfers its pH into our soils, it's just like those white ring build-ups in our bathrooms that also are from water deposits. That's why the fertilizers we apply each fall must contain a high volume of soil sulfur, which counteracts our soil's alkalinity. Hence, our wariness of national brands' winter fertilizing products that are designed for the acidic soils of eastern gardens.

Fans of HGTV or Fine Gardening magazine should be alert to this situation. These are two sources of gardening information where eastern gardening gurus advise the use of lime and potash to sweeten garden soils. Both of these additives do the exact opposite of what our local alkaline soils require. Please, please, please do not use these additives in local gardens; they will kill our soil and plants. I started writing this column for local gardeners because inappropriate national advice was harming my gardens and those of my customers. Trust me, this is the school of hard knocks talking.

Horticultural lime raises soil pH and is perfect for acidic soils. The soil in my own landscape is already in the high 8.6 range. So, with the addition of lime I'm sure I could thoroughly screw up my garden soil. Instead of lime our local soil needs "soil sulfur," which brings down soil pH, i.e., making it more acidic. Be sure to note the percentage of sulfur in the fertilizer you choose for your landscape. The more sulfur the better.

Likewise, although a little bit of potash added to acidic soil is good, bear in mind that Northern Arizona is inundated with vast volcanic ash deposits. Prescott's very own Thumb Butte is the core of a prehistoric volcano. We don't need to add more potash to our landscape.

If you find gardening locally has been difficult, it is usually because all the living soil on your property was removed to build the structures on your property. After your contractor leveled the lot and scraped all available topsoil off your property, you were left with sterile soil. That is the reason I recommend the use of so much organic mulch, compost, and manure for soils of new landscapes. Rebuilding your soil to its living levels is essential. I doubt if you could add too much organic mulch, compost, and manure into local landscapes. If you are a seasoned reader of this column, you will have noticed that I also recommend top dressing a tree's root ball with a layer of mulch or shredded bark. Instead of slinging rocks or gravel back up against the trunk, I find that plants do better if a ring of mulch or shredded bark is used as insulation to protect the root zone and promote a stronger living soil. It really does make a difference.

Once the soil has been built back to its original topsoil levels, organic fertilizers encourage worms, fungi and beneficial bacterial growth that promote a nutrient-laden living soil. Plants love to root into this kind of soil, and gardening in local landscapes becomes easier.

My frustration with national-brand fertilizers led me to create a plant food specifically formulated for Arizona's mountain soils. My "All-Natural Plant Food," 7-4-4, is exactly what our landscapes need right now as we head into winter. I like to use all-natural fertilizers whenever possible, not because they're safer or because they are more environmentally friendly, but because they feed the soil while they feed the plant.

Everything in our landscapes should be fed this fall. It is especially important for perennials, whether trees or shrubs, to be fed this fall. This includes the most important native plants in our landscapes. You know which ones I mean. They add character to a property and, if lost, these invaluable majestic giants are irreplaceable. Fall feeding keeps them healthy, strong and better equipped to fight off their natural predators.

My free gardening classes are every Saturday morning at 9:30. The Oct. 17 subject is "Keeping the Mammals O-U-T Out," and on Oct. 24 we have "Gardening for the Newcomer." Join us for a lot of practical information and an enjoyable time. While you're at the garden center, ask for my handout "Plant Foods: 4-Step Program for Better Landscapes"

Until next week, I'll see you in the garden center.

Throughout the week Ken Lain is at Watters Garden Center, 1815 W. Iron Springs Road, Prescott, and can be contacted through his website at www.wattersonline.com. Ken says, "My personal mission is to help local homeowners garden better in our mountain landscapes."