Author Topic: Building a raised bed/tree: How big?  (Read 2246 times)

Bitterlick

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Building a raised bed/tree: How big?
« on: May 12, 2018, 08:59:26 AM »
Good day--

As I am two blocks from the Gulf of Mexico and storm surges 2-3 times each summer leave a few inches of brackish over my property, I have my citrus trees in raised beds constructed from landscape ties or 2" x 12" PT lumber. In the past I have made the beds 6' x 6' square, but this requires many trips to the box store for bags of compost and soil in my small Fiat.

At any rate, I have just purchased a 30gal Oro Negro avocado, and from google searches, I see many references to avocado trees and 4' x 4' raised beds. The 4' x 4' seems excessively small for sufficient root growth. On the one hand my space is limited and I would be much happier with an Oro Negro that only grows to 12' or so without having to constantly prune it, but I'm not sure if 4' x 4' is ok for an avocado tree, as my experience is that their roots are shallow & wide.

May I know your thoughts?

Mark in Texas

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Re: Building a raised bed/tree: How big?
« Reply #1 on: May 12, 2018, 09:12:56 AM »
Good day--

As I am two blocks from the Gulf of Mexico and storm surges 2-3 times each summer leave a few inches of brackish over my property, I have my citrus trees in raised beds constructed from landscape ties or 2" x 12" PT lumber. In the past I have made the beds 6' x 6' square, but this requires many trips to the box store for bags of compost and soil in my small Fiat.

At any rate, I have just purchased a 30gal Oro Negro avocado, and from google searches, I see many references to avocado trees and 4' x 4' raised beds. The 4' x 4' seems excessively small for sufficient root growth. On the one hand my space is limited and I would be much happier with an Oro Negro that only grows to 12' or so without having to constantly prune it, but I'm not sure if 4' x 4' is ok for an avocado tree, as my experience is that their roots are shallow & wide.

May I know your thoughts?

I recommend bottomless RootBuilder pots which induce a smaller but very efficient fibrous root system.  You control the size.  I just expanded quite a few with some now in 100 gal. pots.  Being bottomless they're not actual pots but a raised bed.  I've also grown outdoors using 2 layers of cinder tree rings. http://tropicalfruitforum.com/index.php?topic=7511.msg96609#msg96609

If you go the RootBuilder route try to buy it wholesale.  Retail prices are ridiculous.

Bitterlick

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Re: Building a raised bed/tree: How big?
« Reply #2 on: May 12, 2018, 12:12:32 PM »
Thanks Mike--

Those do look interesting, and not all that pricey, actually.

I do have quite a bit of pressure-treated lumber, so I think I will go ahead and use it. Is 4' x 4' too small for an avocado tree? I find curiously little info on the internet about size recommendations pertaining to (avocado) trees in raised beds...

Seanny

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Re: Building a raised bed/tree: How big?
« Reply #3 on: May 12, 2018, 01:02:21 PM »
The goal of a raised bed is to keep the root crown dry during a flood. It doesn't have to keep all the roots dry.

spaugh

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Re: Building a raised bed/tree: How big?
« Reply #4 on: May 12, 2018, 01:47:21 PM »
4x4x1 should be ok for a avocado tree.  If you have 8ft lumbers do that.  If you have 10 ft lumber go for 5x5x1. 

Use a heavy soil like decomposed granite if you can get it.  Or a sandy loam.  Don't use bags of compost or potting soil from the store, there's too much organic matter in it that will hold excessive moisture and rot your roots.
Brad Spaugh

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Re: Building a raised bed/tree: How big?
« Reply #5 on: May 12, 2018, 02:17:39 PM »
4x4x1 should be ok for a avocado tree.  If you have 8ft lumbers do that.  If you have 10 ft lumber go for 5x5x1. 

Use a heavy soil like decomposed granite if you can get it.  Or a sandy loam.  Don't use bags of compost or potting soil from the store, there's too much organic matter in it that will hold excessive moisture and rot your roots.

that sounds like it would dry out very fast.
in areas where there is high heat/sun exposure, it would dry faster.
in my raised beds i use about %25 sand (when i can), %25 compost, and the rest local soil
(which is a very fine sandy loam)
it works great. the compost dries fast enough,
 to not cause a problem rotting papaya or anything else

i guess it depends on how tall the bed is, and how often you want to water.
With a tall bed, it could take years for roots to reach deep enough

i have a CORG thats about 14 inches above grade
i have had to mulch the heck out of it,
 and still have to water in dry spells over a week in summer...

spaugh

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Re: Building a raised bed/tree: How big?
« Reply #6 on: May 12, 2018, 04:38:15 PM »
4x4x1 should be ok for a avocado tree.  If you have 8ft lumbers do that.  If you have 10 ft lumber go for 5x5x1. 

Use a heavy soil like decomposed granite if you can get it.  Or a sandy loam.  Don't use bags of compost or potting soil from the store, there's too much organic matter in it that will hold excessive moisture and rot your roots.

in my raised beds i use about %25 sand (when i can), %25 compost, and the rest local soil
(which is a very fine sandy loam)
it works great. the compost dries fast enough

That sounds perfect
Brad Spaugh

spaugh

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Re: Building a raised bed/tree: How big?
« Reply #7 on: May 12, 2018, 05:10:02 PM »
Here's a picture of the native DG soil here.  Its maybe not what people have in mind when you hear decomposed granite.  It's more of a sandy composition but it does retain moisture at the levels avocado prefer.  This is prefer soil type for avocado groves around here.  I use 100% DG in pots for propogating avocado and everything in my yard is in DG top dressed with mulch.  Amending is really not necessary, avocados love this kind of soil.

Brad Spaugh

pineislander

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Re: Building a raised bed/tree: How big?
« Reply #8 on: May 12, 2018, 05:27:05 PM »
 Longboat Key offshore from Sarasota. My first thought would be to search your neighborhood for a successful avocado tree. Avocado doesn't like flooding at all and salty water might be a deal breaker in which case you are stuck with a containerized tree disconnected from the salt. Best avocado growth will be with a lower water table than you have. The main soil available in SW Florida is sand which can be amended with compost. No matter what you should get that tree up at least 1 ft. or more from saturated soil, keep it well drained, fertilized, and well mulched to build the essential fine feeder root system it requires. Last year I lost a few Avocado trees from flooding even though they were on mounds nearly 2 feet high. Higher mounds means greater water loss during dry spells so mulch and water control is essential.
« Last Edit: May 12, 2018, 05:30:50 PM by pineislander »

Mark in Texas

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Re: Building a raised bed/tree: How big?
« Reply #9 on: May 13, 2018, 07:51:44 AM »
Good day--

As I am two blocks from the Gulf of Mexico and storm surges 2-3 times each summer leave a few inches of brackish over my property,

Definately go with a W. Indies rootstock like Waldin.  You can put any pure race or hybrid on it and it does fine.   There's a Texas grower who said he's seen avocado growing in the salty, swampy areas around Cozumel.

Bitterlick

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Re: Building a raised bed/tree: How big?
« Reply #10 on: May 13, 2018, 11:50:01 AM »
Thanks for all the suggestions. I realized that my drop pile was overflowing with 2- and 3-ft sections of 2"x6" and 2"x8" pressure treated boards from recent projects (I never throw anything out, much to my wife's chagrin) and so I spent yesterday afternoon fashioning together a raised bed out of vertical 18" boards. There were enough sections to make the bed nearly 4 1/2' x 4 1/2' square.

Naturally this 30gal Oro Grande has been grafted, but I have no idea what rootstock was used. I wouldn't attempt to do a graft myself; above my pay grade, I'm afraid. I bought the biggest Oro Grande I could find, as most of the growers I called told me that larger trees are at a premium and generally not available right now due to the hurricane back in September.


Bitterlick

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Re: Building a raised bed/tree: How big?
« Reply #11 on: May 13, 2018, 11:56:33 AM »
I should mention that I used native sandy/loamy soil that I dug out from planting four 25gal green buttonwood mixed with a large bag of topsoil and two medium bags of composted manure. There is no issue here with the soil draining; my only concern is keeping the infrequent flooding of brackish water away from the roots.
« Last Edit: May 13, 2018, 05:30:15 PM by Bitterlick »

WGphil

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Re: Building a raised bed/tree: How big?
« Reply #12 on: May 14, 2018, 03:32:56 PM »
I lived on Longboat for a couple years and have seen a foot or more of standing water.  Think we were at four feet elevation with about 200 yards between gulf and bay.

Big mango tree in Durante Park but mango can do water better 


Only thing different I would do is make the box deeper.  Foot and a half would give you more volume and protection and even two might come in handy.