Arizona Soil Issues? - Plants Won't Grow

immobilus(9a)July 9, 2012

Good Afternoon:

I live in Tucson, AZ and purchased a house a year ago. The backyard was completely bare. I have since added some plant life, but have had issues. Plants will not grow. They will flower. They will, generally, stay green. But they will not grow.

Facts about the soil:

Highly Alkaline (8.2-8.5 pH range)

rocky, with slight caliche issues (I break it up with a drill prior to planting)

sandy, with small amounts of clay

In the year that I have lived in this house, I have planted the following:

six oleanders (the same height as when I planted them a year ago, about 1.5 feet);

Two crape myrtles (one died, the other has grown about 4 inches; starting height about 1.5 feet);

seven bougainvillea (died to the roots during winter, began leafing back out in February from the crown. The longest shoot is about 8 inches but most are 3-4 inches. Plants are healthy, just will not grow out.);

two more crape myrtles (planted two months ago, blooms beautifully and are leafed out, but are now growing outward.)

12 butterfly bush (buddleia davidii) (died within a month of being put in the ground.)

I believe the house was built on a lot that previously burned down because the only old tree in the yard has severe burns on it and is growing back from the burn sites. I do not know if this could have effected the soil. Everyone I've talked to, including Lowes, has told me that the bougainvillea, even if it died to the crown, should have been six feet tall by now. The new crape myrtles are beautiful, but still twig like and can barely stand on their own. They are not branching out. The buddleia, which I bought from green things, died, all twelve of them, literally within a month.

There is something in the soil plants either don't like or something not in the soil that plants need. I cannot figure out how to get them to grow outward, vine out, branch out, whatever. I have applied osmocote, I have tried miracle grow, etc.

I amend the soil, while planting, with composted cow manure. I do not mulch because the sandy/clay mixture tends to cake up and suffocate the roots, so if it's mulched you cannot see that happening beneath the mulch to thin the muck prior to that happening.

Is there anything I should top on the soil to make things grow out? The crape myrtles are beautiful, but I don't want blooming tooth picks. The other crape myrtle has been in the ground for a year and has grown four inches. They're all fast-growing varieties *pink valous, red dynamite, and muscogee). The bougainvillea, again, should be long as hell by now. The longest shoot is eight inches...

Do I need to add iron to my soil? What is missing here?

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Consider a soil test. That is the only way to know for sure if you have a soil problem.

    Bookmark   July 9, 2012 at 10:46PM
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haname(z9 AZ NE Phoenix)

Second the soil test.

I amend the soil, while planting, with composted cow manure. I do not mulch because the sandy/clay mixture tends to cake up and suffocate the roots, so if it's mulched you cannot see that happening beneath the mulch to thin the muck prior to that happening.

I would also go ahead and mulch. I'm not quite understanding what you mean by "thin the muck." Can you clarify? Mulch prevents caking and compaction of soil. It helps to keep the soil looser and more aerated compared to bare soil. When there's too much water, the mulch will absorb and hold it. When there's too little water, it will help the soil retain it.

    Bookmark   July 10, 2012 at 11:53AM
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tomatofreak(Z9 Phx USA)

Immobilus, I recommend George Brookbank's book to just about everybody. His advice is essential to gardeners here in the SW, particularly to folks like you who have terrible soil. Read the link below and prepare to dig, dig, dig. And amend.

This is just a thought and might not work for you, but if it were me, I might just dig up the living, but stunted plants, pot them up in a shady spot and start over once you've prepped your planting areas.

Here is a link that might be useful: prepping soil for planting

    Bookmark   July 10, 2012 at 12:35PM
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Pagancat(Phoenix, AZ)

I second the advice to get a soil test. It is relatively inexpensive, gives you a lot of information and comes back fairly quickly. You can get it through your U of A extension service, I think it is probably still up on Campbell. Until you do that, you're really feeling your way around in the dark. You should also let them know about your specific issues, there might be extra testing they can do for some common chemicals. Burning in and of itself should do no harm, only add to the alkalinity of the soil, but who knows what they used to suppress the fire...? No idea if that would affect it or no.

Your soil will cake up if you are working wet clay, a big no-no. The mulch and compost is great for softening the soil and make it more moisture retentive, so checking it wouldn't be a big deal, and even then you can just scratch a little back. Mulching is *huge* in desert gardening, be it organic or even rock - anything to aid in cooling the roots, especially of non-desert plants of the type you're planting.

I'm guessing you're saying that your soil is a mixture of sand and clay and not that you're mixing the two - that would = cement, and could be a part of the problem.

Have you seen any of your plants growing well in your neighborhood? Also, longer term residents might be able to tell you if something happened on your site.

But from your description, my best bet is that the holes that you're making in the caliche may not be sufficient to let the roots spread out; you might want to dig one of the dead plants out and see if it stretched out beyond the original root ball, or did they run into caliche immediately? You also want to test your drainage - caliche tends to form in sheets and if you had to get thru one, there is a good chance of another below it. Anywho, "they" now say that it's much more important to make a wider hole than a deep one, for the root spread problem precisely.

BTW, I wouldn't waste my time asking folks at Lowe's for plant advice, although they put a few through some master gardener classes, few have the experience to do much more than scratch the surface of gardening. And steer manure... well.... unless it's really well composted, you're adding a lot of salt to an already salty soil. I saw an ad on Craig's list for horse manure today, you might think about that or the city of Tucson used to make compost out of their clippings and give it away.

Hope this is helpful, best of luck to you!

    Bookmark   July 10, 2012 at 5:54PM
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It might be too soon to panic. The first year or two after planting, most trees and shrubs do NOT put on a lot of top growth. They are working on a good root system.

STOP FERTILIZING until you find out what the soil really needs. Definitely get a soil test ... and if you need to lower pH, "soil sulfur" applied liberally all over the yard is the best way.

I amend the soil, while planting, with composted cow manure. Bad idea - you are creating "flower pots" of good soil and the roots will stay in that area, hindering growth. The preferred method of planting is to dig a wide area of native soil, as deep as the root ball of the plant, fill the hole with water and let it drain. Then place the plant and backfill the hole with native soil.

To fix this, loosen the dirt in a wide band around the edges of the hole you amended, mixing the native soil into the compost-amended part.

I do not mulch because the sandy/clay mixture tends to cake up and suffocate the roots, so if it's mulched you cannot see that happening beneath the mulch to thin the muck prior to that happening. That indicates a watering problem, not a mulch problem. Mulch should prevent the caking if the watering is OK.

What's your watering schedule for these plants?

    Bookmark   July 11, 2012 at 10:36AM
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Hi Guys:

Sorry it's been so long for me to respond, and great advice. I will definitely contact the U of A extension and see what they can do.

Lazygarden - water schedule... hmmm... Well, I have two crape myrtles in my yard that I purchased at Lowe's. They are single trunked and are blooming beautifully, but if they are not watered every day the leaves hang like they were just liberated from a labor camp. I can't figure that one out. In fact, two weeks ago I took my shovel, dug around the root 'buckets' of them, and added more amendments to the surrounding soil. They are all mulched now. But sell, they need water every day no matter if it's 90 degrees or 109 degrees. In fact, they get brown lines around the leaf edges if not water heavily every day so I leave the hose on a very small trickle, enough to keep the ground damp, and throughout the day move the hose between the two. Obviously, I can't do this forever - but I can't seem to get them to establish. Also, the new growth is lanky and weak... the trunk doesn't seem to be thickening and the new branches do not seem to broaden. I'm not sure if this is some sort of mineral deficiency.

As for other plants in my neighborhood, yes. There are HUGE oleanders, so I don't know what's going on with mine. Also, there's a bougainvillea on the street outside someones gate that i hacked up earlier this year for cuttings and it has already grown back. I've never seen it get any water except for rain, but it grows and grows and grows. The ones in my yard die within three to four days if not watered every day.

I tried added gypsum to the soil per recommendation of Lowe's, and I'm not sure exactly what that did. I've considered sulphur (my pH level is in the 8.5+ category, super alkaline), but I've heard sulphur applications can take years to actually acidify the soil.

Further help is greatly appreciated if anyone has any other advice to share.



My garden is on it's way - i have planted a lot of beautiful things - they're just not growing.

    Bookmark   August 17, 2012 at 12:58AM
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tomatofreak(Z9 Phx USA)

I just bought some plants and the woman at the nursery talked me into buying some soil sulphur amendment that looks like split peas. I'm hoping it works as I'm not having much luck growing stuff in the ground.

    Bookmark   August 17, 2012 at 9:43PM
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immobilus, Your crape myrtles are just stressing from the heat. Thats why they are drooping and this has nothing to do with watering. I water everything in my yard about every 3 days and everything does fine. Trees I water once a week. Crape myrtles will take time to acclimate in Az, especially if you planted them during the summer months. Mulching is a must! Also, as the mulch breaks down it will amend the earth around your plants. One other thing, gypsum is about 60-80% sulfur depending what brand you purchase I believe. If I were you I'd wait for the Fall to start planting again. Summer is just to brutal. Best if luck to you! =)

    Bookmark   August 17, 2012 at 9:58PM
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I live in Tucson in a home built in '78. I had the identical problems. I now dig holes that are about 7-8 feet wide and 2 feet deep for even the smallest trees and do all sorts of amendments. I've also given up and put stucco planters that ring our backyard. That worked very well. I do wonder if there's something in our soil that's unusual. I know that the previous owners sprayed weed killer over the entire lot every month for 20 years. Their idea of Xeriscaping. We didn't see a single weed for the first 10 years that we were in the house.

    Bookmark   December 31, 2013 at 12:38PM
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You could be on the right track. They used to sell a product called Triox that was marketed as a total vegetation killer. It kept things from growing for years in areas where it was applied. Plus it moved with water (as in rain) and then affected areas that were close by. Only a chemical analysis of your soil would tell you for sure and after so much time has passed it might not be worth it. There is no remedy except what you've already done.

    Bookmark   January 2, 2014 at 12:27PM
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