I was told that my back yard needs to be kept watered to prevent cracking of the soil, thus making the ground unstable

If a licensed geologist or soils scientist told you that, I'd take the comment seriously, but otherwise I'd be extremely skeptical. You may simply be wasting water by over watering. Are you on a hill or a cliff?

The easy way to make hard soil workable and good for plant roots is to mulch frequently with a quality organic mulch such as compost or composted shredded wood or bark. Over the course of a few years, earthworms will work the mulch into the soil and create really wonderful soil that is easily dug, and you won't have to lift a finger other than to toss mulch around once or twice a year. In addition, mulch holds moisture in the soil, so you won't have to water so much.

As to Avocados, they love water and are fairly thirsty trees, so unless you are in what used to be a swamp or bog, I'd be thankful your soil holds some moisture, and put the tree in the ground. Keep the root area thickly mulched, because Avocados like their root systems kept cool and shaded.

I would risk planting the avocado in the soil. They will not grow in containers- their roots hate to be hot and don't like disturbances.

You don't have to keep the soil wet, just keep it from completely drying out if possible. As hoovb said, you can do that by using a heavy layer of mulch.

Renee

I did get a geologist report regarding my soil, and it was fairly dry and somewhat cracked when we bought the property almost three years ago. Now I think we are overwatering. My brother has been wanting to have a compost heap, and so maybe I will let him have one in the problem area.

Do you think burying shredded wood or bark would be enough? How deep would be it need to go? I'll probably have to put the avocado tree in the planter temporarily, although maybe I will put it in a pot if I will be able to transplant it again in a year or so.

I'm not so much on a hill as just high ground, with the front yard sloping down to the street. The back yard is fairly flat and at pretty much the same level as my house, but the neighbors are very slightly down hill from my back yard.

Thanks for your help - I'm definitely going to start mulching that part of the yard.

Lars

Nature does not like bare soil,mulch all bare soil. Most areas of California the waste management company turns yard waste into mulch to prevent putting it into the landfill. They sell it very cheap and often can deliver it, if you buy enough. As hoovb says your soil will get better every year. Al

About the compost heap: When my house was built, they had scraped off nearly all the topsoil, leaving only the subsoil, which was this sticky yellow clay. One thing that I do on areas which I haven't planted yet to help improve my soil is to build multiple compost piles on empty spots, and once they reach a decent size, cover them with a layer of burlap to prevent them from drying out and leave them to break down for at least a few months. It's not the most aesthetically pleasing, but I don't have to spend money buying compost to amend the soil and the pile acts as a mulch to keep the soil covered. Now, after 5 years of composting, the soil in my vegetable garden dark brown crumbly, and full of earthworms.

My soils cracked until I put enough organic matter in them to hold some moisture, then improved further when I started building up the mycorrhizae (fungus) populations and generally feeding the soil food web a more healthy diet. That didn't happen overnight and I found that garden engineering was often more important than ground-level soil amendments in saving my plants from drowning.

Just because no one has mentioned it yet, you do have a pollinator tree nearby, right?

Don't bury the shredded wood or bark, publickman. It goes on top of the soil. It will break down better that way.
Renee

I do not have a pollinator tree for my avocado, although there is another avocado tree about three doors down. From what I read about avocados, they can be self pollinating because the flowers change from one sex to another in one day or so. I also read that it was better to have a pollinator tree, and I probably do have room for that.

If my soil does not drain, should I mix it with sand instead of the mulch or shredded wood? I won't be able to do much this week-end because I came down with a bad cold this morning and missed my dental appointment as well as work. I hope my brother can do some of the back yard work this week-end, but at least I got a lot of good ideas here. I won't transplant the tree until we get the area under control as far as moisture goes. I think mulching the area will be better in the long run than paving it, as we have enough paved already, and I do prefer planting in the ground, if at all possible.

Lars

Give up the idea of adding sand, you could not possibly add enough to help, and what you do add, would make it worse. Avocado trees although they have the ability to be self fertile, seldom are. If other trees are close by you may not have a pollinating problem. Al

No sand! Sand plus clay makes terra cotta pottery. You want organic material, and there is no quick fix, unfortunately. There is a quick fix for overwatering, though. Just make sure it's not constantly mucky where you plant your tree. You can also plant it on a mound so that you get better drainage. Put plenty of compost over the root zone then top with shredded bark or leaves.

We took your advice, and my brother bought a gas powered tiller and tilled the soil around where we wanted the avocado tree. Then he added a lot of compost and planted the tree in the ground and added more compost and bark. He dug a big hole first and put a lot of compost in that, and so I think we might have a fighting chance. Anyway, I am much happier with it in the ground than in the planter. I checked to make sure that there is a large avocado tree two doors down on our side of the street, and so I think we should not have a problem with fertilization, although our tree might have to get bigger first.

I've been sick with a bad cold since Friday, and so I was unable to help with the planting, and now my brother is also sick - there is something bad going around. I mention this because this post might seem a bit incoherent.

Thanks for all the help!

Lars

Your newly planted tree is very likely to sink as the compost added to the soil under the tree breaks down. I hope you built up a berm to plant it on to account for this sinking. Avocado tend to be shallow rooted so be careful to maintain soil moisture through the coming summer. Al

I hang out in the soil forum and my understanding is you need to create some drains before you plant trees. This process is very complex and expensive. I have sandy soil. These drains start with channels or maybe tubes filled with gravel. If I had clay I would only plant tress that like clay and will accept poor drainage rather then fight with nature so much.

I didn't know there was a soil forum - I'll have to check that out. However, I am not interested in putting in a complex and expensive drain system at this point. I didn't spend that much on the tree, and I think it has a fighting chance of making it. I had an avocado tree in Venice, and it grew perfectly well in the clay soil there, not that far from where I am now. The only problem there was the white flies, which were prevalent because we had too many hibiscus bushes. I only have one hibiscus in the back yard now, and it is in a wine barrel planter, in case I need to move it. I have another one in the front yard, but it is growing rather slowly, possibly because of the clay soil. I might consider some drastic landscaping changes in a couple of years or so - after I see how my current experiments work out. I did grow up on a farm (in Texas), but I never considered myself a farmer.

Al, I did build up a berm for the avocado tree, as I did expect the compost to settle or break down. So it's on a bit of an artificial hill at the moment. There shouldn't be a problem of not enough moisture, as it gets watered by the sprinkler system, and in fact I want to learn how to reduce the amount of water that comes out of the sprinklers. At this point, I think it is late enough in the year that I won't have to worry about it immediately, but I do want to figure it out eventually.

Lars

I think that your tree will be fine. If the bark starts to look black, it's probably sunburn. Young avos get that sometimes, and you should paint the bark with latex paint or rig up some light shade if the tops of the branches start burning.
Renee

It is called a french drain. You can search on how to make a french drain in google, if you want. But, you need to do it before you put in the trees.

Trees love clay soil as long as it is well drained. Clay will contain more nutrients than any other soil. Sand on the other hand drains so fast, it is the least able to keep nutrients from leaching out of the soil. When I lived in San Francisco we had a terrible problem with the joint grass, native to the sand, entering our clay sewer pipe in search of water. Al

I did notice in the planter in which I put some small daffodils called rip van winkles, they did better in the planter in which I put clay then in the ground that is sand with a lot of compost. The flowers in the sandy soil failed to come to fruition. I don' know maybe I should have used the bone meal after all on them.

(I didn't recall a soil forum either)
fwiw, i agree with the replies. (no sand, don't bury the organics, use berm). perhaps planting in a berm *and* on front yard slope would have been better, but if the slope falls away just behind your fence (avocado location?) then that should help.

common fruit trees can grow very well in pure "cracking" clay.

the plums may have needed a pollinator. there are compatibility charts in those garden department books (also public library). (looking now...) sunset book names a few pollinators for each cultivar.

Here is a link to some more information about growing avocados.

Here is a link that might be useful: Master Gardeners of Orange County - avocados

You are on a high spot, the tree will be fine. There is nothing at all wrong with clay soil--it holds and contains more nutrients than sandy. Current thought is to plant trees in native soil only, and just mulch with compost on the surface, but your tree will probably be fine.

I do not have a pollinator tree for my avocado, although there is another avocado tree about three doors down.

That's close enough, though it does depend on the type. Check the Sunset Western Garden Book for which Avocado pollinates which.

Hope you and your family member are feeling better.

Try using gypsum, farmers use it for that reason. It is a seasonal product but you may still find some at a tractor supply store or even ace hardware. It is great for compost and flower beds,you can research it you will be surprised how many uses it has. We use it for our yard where the drainfield is located to keep the ground from becoming clay bound again so the ground is able to absorb the waste. Inexpensive & works, hope this helps.

I know your soil. I had it. Was like concrete when dry. Here's the magical secret: manure, leaves, grass clippings. Layer them on good. Whenever I planted something there was a huge hole dug, lots of dry leaves and composted manure put in the bottom, clay soil to fill it half way, layer of leaves, manure, etc, then clay. It has never failed me. One you get the soil right, the rest falls in place. No fertilizing, no pests.

By the way, after about a year of heaping that mix or some similar combination on the soil, I had wonderful workable, fragrant humusy soil. Clay is the best when lots of organic stuff is blended in. It is evidenced in my oversized flowers, fruit, and hearty everything.