Building up a Mound for drainage

[reinerio1]

I live just northwest of Austin, TX.  Zone 8B.  At the edge of what is called "Hill Country".  My soil is clay, with bedrock about 3-4 feet deep and my soil does not drain well.  During the 3 summer months the average high temps range from 95-100F.  Winter day average is 60F and night average is 40F but we get about 10-15 nights below 32F and about 3-4 nights temps dip to low 20sF.  Every 5 years or so night temps get below 20F.  

I have various size 10 and 20 gallon cold hardies (Butias, CIDP, Filiferas, Jubs, hybrids) to plant.  In Central TX we get periodic extensive rains in winter between periods of semi-drought.  Since my babies do not like wet feet, especially in winter, I need to be concerned.  I plan to amend the soill and to place the babies on a small mound to have better drainage.  I have already prepared the amended soil (small gravel, woodchips, sand, etc.)

What should the mound look like?  

How far deep should I dig the hole?  

How far off the ground should the base of palm be?

Should I dig about 2 feet, amend about 1.5 feet , place palm, and then fill in all around the base with amended soil and cover up with amended soil to the the base of palm.  

Should the final result look like a little volcano-like structure?  

PS, should I also mulch in both witner and summer or only summer?  

Any suggestions with photos will be helpful.

[osideterry]

Bump!

Maybe we can lure SurferJr away from the "Plants and Seeds for Sale" forum to share his method. Can't argue with his success in heavy clay soil. He doesn't dig very deep. I asked him if it would help to dig deeper and amend, but he thought it was unnecessary. Mounds up amended soil to ground level of potted palm, and then buries with pine mulch.

I'm planning on mound-planting 20-25 palms this Summer, and am very interested in what experienced growers have to add.

[BS Man about Palms]

I thought I had mentioned it to you before Terry, but I read an old Australian Palm and Cycad book a long time back and it said if you had some rare palm, etc you wanted to make sure it lived, it said to set it on the ground and mound around.  Nothing new.  

[osideterry]

I really don't see many people doing this. Occasionally you see a raised bed bordered by rocks or garden wall. The normal pro advice is an elaborate hole, with a french drain or extra trench involved to divert water.

Most of my palms are 5 gallon, so the volcanos won't have to be that tall.

[Wai`anae Steve]

Most of my palms are on terraces and if so I dig a trench and fill it w/cinder, I guess any gravel would work.  I don't add anything to the soil as that might discourage the palm roots from leaving the "good stuff".

I'm also into "pot" planting now.  I just cut off the bottom of the pot and plop it in the hole.  Then I fill in w/native soild.  I do mulch heavy w/compost from the local recycle center.

[Steve in Brookings]

I'm sure that different climates and soil types favor different approaches.  Above-grade planting provides good drainage for the root zone, but also dries out quickly in hot weather.  Below-grade planting provides increased water retention...but maybe too much if you have slow soil percolation.  Keep in mind the following practice is what has worked for me in a cool-summer West Coast climate.  

I just scuff the turf off the top of the site to expose some soil.  Then I set the rootball on top and mound around it with decomposed wood chips.  The palm will find its own level with time.  One of mine has pulled itself further down into the soil even though I thought it might want to be more elevated.  Mother Nature knows how to make those kinds of corrections.  Earthworms will come up and work through the wood chips at night leaving castings behind, thereby softening the abrupt interface between soil and mulch as time goes by.  So you will end up with a good deal of mineral soil in the mounded mulch after a year or so.

 

I wouldn't dig a planting hole and then amend it.  That will only lead to the dreaded planting-hole Bathtub Syndrome.  Set the palm over undisturbed dirt, keep it well mulched and well watered, and the roots will find the proper drainage horizon in the native soil.

[osideterry]

Thanks Steve for the extra info.

I've been doing online research, and I'm never digging a hole again. One source said if you dig a hole and it takes a long time to drain, try mounding instead. Hello? I don't think a hole dug anywhere in my yard would drain in less than 24 hours.

I don't plan on starting until June, when the ground starts to warm up. I can't wait to see actual growth occurring for a change. I've had a caryota urens in the ground 5 years, and still no trunk.

[Walter John]

(reinerio1 @ Feb. 27 2008,14:28)

QUOTE

I live just northwest of Austin, TX.  Zone 8B.  At the edge of what is called "Hill Country".  My soil is clay, with bedrock about 3-4 feet deep and my soil does not drain well.  During the 3 summer months the average high temps range from 95-100F.  Winter day average is 60F and night average is 40F but we get about 10-15 nights below 32F and about 3-4 nights temps dip to low 20sF.  Every 5 years or so night temps get below 20F.  

I have various size 10 and 20 gallon cold hardies (Butias, CIDP, Filiferas, Jubs, hybrids) to plant.  In Central TX we get periodic extensive rains in winter between periods of semi-drought.  Since my babies do not like wet feet, especially in winter, I need to be concerned.  I plan to amend the soill and to place the babies on a small mound to have better drainage.  I have already prepared the amended soil (small gravel, woodchips, sand, etc.)

What should the mound look like?  

How far deep should I dig the hole?  

How far off the ground should the base of palm be?

Should I dig about 2 feet, amend about 1.5 feet , place palm, and then fill in all around the base with amended soil and cover up with amended soil to the the base of palm.  

Should the final result look like a little volcano-like structure?  

PS, should I also mulch in both witner and summer or only summer?  

Any suggestions with photos will be helpful.

If I were you I'd truck in 8 cubic metres of sandy soil, box it in 2 sleepers high, plant your palms there and cover all in 2 feet deep of sugar cane mulch, recite the Lord's prayer, or "Canopy of Palms" by Wal Donovan, whichever comes first, with one hand tied behind the back of a xxxx stubbie. Does Bob Schneider live near you ?, I want his autograph or he wants mine, can’t remember which.

[_Keith]

Here in my part of So. Louisiana we have clay soils, periods of heavy rains and it is very flat so mounded planting is recommended.  I started with high mounds, 12 inches.  What I found was that during dry times in the heat of the summer I could not keep things moist enough and was losing plants.  

With our summer heat, you have to stike a balance, unless you are a very diligent waterer.  I live on a large plot so supplemental water is a big chore.

Now, I plant between 2 and 8 inches above grade depending on the individual plant's tolerance of wet soils.  

Most of my palms are in the 2 to 4 inch above grade level and I have yet to lose one

There a couple more things to do in clay soil as well.

*Shake as much of the soil from the potted plant as possible out before planting

*Don't amend the soil, backfill only with soil from the hole.   If you need additional soil back fill to grade with soil from hole and then add above that with other soil.

*Heat and moisture here break down organic matter very fast in the south, so within a year or two at max. so all of the soil the plant had in the pot will be gone.  I put a small chunk of clay soil on top of the root ball every few months to wash down to replace the organic matter.  

And mulch, mulch, mulch.  It won't stop the weeds down here, but it will moderate soil temperatures and moisture levels.

[PalmGuyWC]

When I moved to Walnut Creek about 40 years ago, I had about 2/3 of an acre of raw land to play with. There were three large Oaks growing on the property, and a tall Ivy hedge cutting off the house from the rest of the property. The first thing I did was draw up a general landscape plan and it took me several months to do this.  It was a very general plan, nothing palm specific, but my idea was to have 3 "islands" or mounds densly planted and with vistas that could be seen from the house to the back of the property. I had seen to many palm gardens so densely planted that you couldn't see the palms for the jungle.

A swimming pool was quickly built, and the excivation from the pool was the soil for the mounds.  My soil is adobe clay, and the first summer the mounds hardened into concrite.....as hard as a rock. There were many other projects going on, a green house, decks, the garden plan, so the mounds were neglected the first year.

I soon realized the rock hard mounds would require tons of soil amendment, and truck loads were brought in....maybe 50 truck loads over a couple of years. I had an 8 HP rototiller, and I must have struggled 100 miles behind the tiller as the soil amendments were brought in. Soon I had mounds with nice pliable soil and they were ready for planting.

I guess I'm from the old school, but I always dug a huge hole with plenty of amendments, and then made a 6" berm around the palms to hold water. I would put 6" of amendment down, then rototill it untill I had a nice mixture, then dig it out with a shovel, then add more amendment  and rototill deeper. Usually I could dig the hole out with the rototiller and also have nice amended soil to fill in around the palm. This method worked for me, and the palms never missed a beat in growth once their roots hit the gound.

When I constructed the mounds I wasn't thinking of drainage, only of the effect, and over the years I can really tell no difference in the palms growing on the mounds and the others that are planted at grade. Butias and Trachycarpus  and other palms have grown at the same rate.  My Jubaeas, Braheas and Sabals are all planted at grade and they have done very well. One Trithrinax at grade and the other on a mound, and they have done equally well and the same for Nannorrhops.

Dick

[BS Man about Palms]

I fall back on one of the early statements. Depends on the plant, some could care less, they just want to grow. Its when you are "pushing zones" the mounds become more important.  I would almost venture its not important to any palm that is rated zone 9 hardy. !

[tropicalb]

When Bill trucks in the 200 yards of soil it's gonna take to plant all the palms at his place, THEN you will see some MOUNDS!!!!

[sonoranfans]

All my palms have been planted in ammended caliche clay, originally 100% clay, its trucked in and spread 4' thick on every homesite.  The clay is so hard that when its dry an overhead shot with a pick axe will get you 2" penetration.

Planting palms in clay will depend on your climate.  What works here in dry AZ will probably not be best in socal, and what works best in socal will probably not be best in a wet place like texas.  Texas will need the most mounding, for sure as its the most wet by alot.

What I do is look at the slope of the ground, high spots will need less mounding, low spots much more.  I dig a hole 3-4x the size of the rootball and up to 2x as deep, (depending on whether its a high or low spot) and ammend with up to 40% sand and pearlite.  Mounding is typically 4-6" if I do this or more if I dont dig as deep, but again we generally have dry winters(4" rain).

I also treat the soil with sulfur to react with the clay and form gypsum over time, which drains better.  Over time(5 years) it will change the soil content, break down the clay into gypsum.  You can install 3 pieces of 2" PVC pipe(8" length) in the ground when you plant to keep the sulfur within the root zone.  This will prevent run off and ensure that clay is broken down in the root zone area in time.

If I lived in texas, I might try 12" mounding and dig channels that drain away from the root zone around 3' and ammend the channels in the mound more heavily with sand, pearlite, this will give you faster drainage than just mounding for times when it rains alot.