Sandra I really hate to mention this and I don't want to freak you out. However I have a concern that may or may not be valid.

Long ago I had to do some trenching near a mature palm tree. The tree was obviously a different variety than your trees as it was roughly three foot in diameter and about over twenty feet tall.
Its root system was a mass of finger thick fibers that were like digging through a mass of tangled ropes. I had to chop through it with a pick and ax every bit of the way. I seriously doubt any tree planted near it would have thrived or even lived long for that matter.

My hope is that the roots from your palm trees are different but the only way to tell for sure is to dig a few test holes.

As far as multi tree per hole planting goes there are some things to take into consideration.

Below here I will just pretend the palm trees never existed.

First of all yes you can plant four trees in a 5'X5' or 6'X6' area. It can be done but it is a lot easier if your trees can branch out of the 5'X5' or 6'X6' hole area. But even if they can't its still doable you just have to stay on top of your pruning.

For best results all the trees in any given hole would be approximately the same size and be growing on the same or similar rootstock and be planted around the same time. Plant older/taller more mature trees behind the smaller trees in such a way that the smaller trees will get more sun rather than the other way around.

There are many reasons for this and here are a few....

If one of the trees has a more precocious rootstock its roots will grow faster and starve out the other trees.

If one or more trees are planted and another tree is planted 6mo-1year later their root systems will be more established and may end up starving out the newly planted trees.

If a larger more mature tree in planted in the dominant position where it will receive more sun then it will soon block out sun to the smaller tree planted in its shadow.

You may want to consider a barrier on the lower part of each tree hole to help with soil erosion.

You may also want to think about going to two rows. I know it measures out to 21' deep but this is a slope. My bet is the horizontal measurement is a lot closer to 15' and that 15' is what you really have to work with.

Sandra: The thing we can't judge for you is how vigorous your site will be. I have a low vigor site and am converting from 6ft by 8ft to 2ft by 8ft. I think the new spacing will work. The old worked by pruning every 6wks. I think the new will as well. My height is about 8.5ft.

Where you get into trouble is if the site is so vigorous that you aren't getting much fruit bud set, just massive vegetative growth.

It will be easier to start out with the 30 trees but you can probably make 60 work. Planting 60 trees on a 3ft by 7ft spacing will be a challenge. I'd space the trees out like that rather than two closer together. It will be easier to keep the more vigorous from shading out the weak growers.

Don't apply any fertilizer unless you can see a deficiency. And don't over water. Both will cause excess vigor and can reduce fruit eating quality.

Good luck!!

The Fruitnut

Hi, Sandra! I have a backyard similar to yours, except my slope is 18 degrees where yours appears to be 25-30, and my yard is 100' wide. There I have numerous clumps of fruit trees that are flourishing. So, yes you can do it.

It will be crucial to remove not only the big trees, but all the brush on the back fence that is shading your plot. Your trees must have (nearly) full sun.

If your soil is unworkable due to dead roots or other reasons, you can build circular raised beds about 18" deep and 6' across. I recommend three trees per clump, all of the same rootstock and similar vigor. If you mulch your beds with, say, woodchips, they'll hang onto the side of the hill remarkably well.

You can plant your clumps two deep and four or five wide. Also, if the lighting requirements are met, you could espalier trees on the fences.

I pretty much agree with thisisme's comments. Traditional growers may follow and give you lots of reasons why this won't work. For more reasons why it will work, go to the Dave Wilson Nurseries website for good text and videos.

Happy New Year, Misterbaby.

Thank you guys for your very valuable input. It's good to know that 60 trees is doable. I had questioned if 30 would work but if you say that 60 will, 30 sounds great. I might try to do a few in the same hole just to experiment. I have several peaches of the same variety, size and rootstock to try with. Also a couple of plums and apples.

My boyfriend almost fell off his chair when I mentioned the 60 trees. Guess we're going with 30. lol Afterall, there's only the 2 of us to feed. But as you all know, it's so hard to limit yourself on the type and varieties of fruit trees to grow. I want them all!!! :)

We're working on the slope slowly as we can. Everything is coming out except one of the palm tree where the owl box will go for rodent control. I hope to not have such an issue but...

Thank you all for your inputs and suggestion. You guys are awesome!!! :)

Sandra

I agree with misterbaby. Make sure you comb through the davewilson.com web site and become familiar with backyard orchard culture, successive ripening and such. By the way, 60 trees will be a lot to prune, thin, harvest and keep critters out of.

My three to a hole plantings have 18" spacing between trees and hedgerow trees are planted 4' on center. Citrus are spaced at 8'. Hope that helps!

Here is a link that might be useful: What Is Backyard Orchard Culture?

sk
a couple of things to consider. Fruitnut is right about the "vigor" of the site. What I see in the pictures is a lot of shading and Dana Point is already a low sun location because of being so close to the beach. With limited sun, you don't want to crowd the crowns of the trees and have them needing more sun.
The second point, multi planting is helpful when you only have room for one hole or one planting space. when you have a whole area, not just one spot, you are better off spreading the planting out so the roots compete less and pruning and shaping the trees will be much easier. you still need a given amount of space for the top of each tree to grow, spread the roots out too, don't plant them in the same hole.
If you want to go high density, spreading the roots is better, even if the crowns are just as tight.
You still have the sun light issue, so I don't think high density is a good choice for your area, but if you do try high density, you still would be better off planting the roots apart instead of one hole method.

I agree softmentor, I don't see the advantage of crowding the trees together. Spread them out evenly if you can and there will be less trouble with vigor differences. I also think 30 trees is enough in this area for someone with little high density experience.

I've been planting high density trees for more than 30 yrs. But I've only learned the finer points in the last 10 yrs.

The Fruitnut

Softmentor/fruitnut,

Those are good points! I was also concerned about the airflow through the canopies and the possibility of fungi due to poor circulation. I'll stick to the original plan (5'x6' or so).

Mrclint,

Thanks for the DW link. Lots of great information there!

Thanks everyone for your opinions. I'll post pics as the slope is cleaned out and the plants planted. :)

Sandra

Fruitnut, how about a summary of those "finer points"?

"My boyfriend almost fell off his chair when I mentioned the 60 trees. Guess we're going with 30. lol Afterall, there's only the 2 of us to feed."

That was my first thought. Now that I know there's only two to feed even 30 may end up with too much.
There may not be a problem with too many, you can always give them away or sell them, but often when you overload a hobby you turn it into work then you start ignoring it.

Dana point is a wonderful town. I worked there for a time a few years ago. If I recall correctly it had above average sunshine for most of the year. If you stick with low-chill varieties you should be in good shape.

Here is a link that might be useful: Lots of fruit on a slope

A naive question please. How is planting several trees in a single hole more beneficial from digging separate holes with the trees spaced just as close? A tad confused.

how many holes doesn't matter, its how close they are. If you are putting them really close its more or less impossible to do unless you dig one big hole for all of them -- the roots are too big otherwise.

Scott

Hi, Scottfsmith. Ah, thank you so much for the clarification! We, too, are interested in many more fruit trees than we have space in the garden for. Hence, this method may work for us too. Thank you! :-)

Hi, Sk290. Can't wait to see your new garden once you have your fruit trees planted. Wish we could have 30 fruit trees too! :-)

For clearing the slope, Thisisme has some good points. A good pick and axe may come in handy. We used them for our small palm trees, including a sago palm which is similar to the one in your 2nd photo.

We had a ton of roots beneath what we had to clear... If you want to clear the vegetation like the grass, etc., try RoundUp. Works great on contact with the leaves to kill grass, weeds and smaller plants down to the roots. It will make the work a bit easier and has quick results too.

There's a lot of work ahead for you. Happy Gardening nonetheless. :-) Just remember that it will be worth it once you are done! :-)

Sounds like you have caught the dreaded, "if one is good, 30 are better," disease! There is NO cure!! Stay away from the UC Davis site, or you will be swimming in cuttings like me! My home vineyard started with 7 wine grape vines, and I now have 80 viable cuttings (some going into containers,) and some tucked in every corner of my yard I can find. Make wine out of your fruit, and your boyfriend will soon get on the "let's plant 60 trees page."

I am now going to keep in pots a few fig trees, pomegranates, and olives.

UC Davis is a humbling place because for the cost of shipping, they send you cuttings for Free, and when you get them, you suddenly become very spiritual and pray more than you ever did, that these precious living things bestowed on you will grow into mighty thriving plants. God started this whole thing anyway, with his Garden of Eden! Where is that place? Dana Point?

I wish you sunny days, and the best of luck with all of your trees!

Here is a link that might be useful: Shop for Cuttings at UC Davis