Planting tillering (heeled) palms on a hillside

[Mauna Kea Cloudforest]

OK, my garden is on a southwest facing hillside, and the soil is fast draining sandy loam. So far, the only way I've managed to keep any plants alive is by terracing a swale into the hillside so that whatever I plant is slightly below grade. It's the only way I can keep anything moist enough. For those who don't know what that's like, let me tell you: from about 1PM to about 4PM, the sun hits the hillside at pretty straight angles, and it gets super hot. Soil temps run in the 80's, and it's hard to keep the soil moist. Even in the Winter everything dries out rather quickly.

The swale, i.e. planting slightly below grade with respect to the lower end of the planting terrace helps to keep palms moist and fertilized. Yes, the fertilizer also disappears quickly down the hill, the swale helps to retain the nutrients longer.

So this brings me to heeled palms, and more specifically, dypsis. I have to plant these in holes, especially the small ones. But the darn things grow themselves into the hillside, so I end up having to dig a deeper swale to keep the trunk bases clear. i planted a dypsis decipiens liner in the hillside a couple of hears ago, and it's growing straight downward. Ultimately, the whole thing is still above grade since anything on the hill is theoretically above grade at some point. But it's making me wonder about this setup.

Planting on a mound on a sandy hillside exposed to the hot afternoon sun is not an option. Are my heeled palms doomed?

[Kostas]

Heeled palms are adapted to get their growing point deep in the ground and adjust the depth of their growing point according to the soil composition and their needs,as do remote germinating palms,so they want the part of their trunk they produce underground,to stay underground and produce roots for extra stability. So there is no reason to dig out the trunks of those palms as long as they do well. Even though there is theoritically a higher chance of rot,these palms are adapted to that and generally don't have problems.

[Phoenikakias]

Wouldn't that swale collect in winter rain water in larger quantities than wished? I am facing the same situation in my garden (slopy with orientation south-west), but truth is that native soil is clay with great water capacity and even greater in some points. So I feel bound to use a very porous medium to greater depth when digging holes for more tender palms. But I never make a swale in those cases because of the above reason. So far I had no problems with the porosity of soil in summer or the lack of large bowls, since irrigation water penetrates faster this porous layer and in fact I use more water for such outplanted palms. If I need to keep also surface moist in summer I better use mulch in form of pine bark combined with pumice as surface material (our pumice has the ability to absorb moisture and release it slowly) . As for the slope either I make a terrace (that is kinda a mound on the lower side of the hole), which is supported by bricks and stones (fig 1,2,3), plus excavated native soil and all those materials (stone, bricks, native soil) offer some insulation against heating soil. Or I take care that the side of hole downhills is on the same level with native soil, and in latter way soil temps maybe will be more independant from external elements. Last method I applied experimentally on an outplanted Thrinax (fig 4 and 5) with good so far results. But eitherway excessive rain water is allowed to flow downwards freely. I your particular case however intial situation seems reversed, since native soil is supposed to be fast draining and good warmth conductor. Maybe you follow second of the describe methods plus mulch in summer. If I have understood wrongly your problem I will be very glad to read more details from you.

Edited March 31, 2013 by Phoenikakias

[Darold Petty]

Axel, why don't you plant them with the tillering direction perpendicular to the slope? (Like the contour lines on a topographic map) Remember that the 'heel' point remains fixed, and the enlarging diameter of the stem moves away from the heel. Thus it is easy to determine the direction the palm wants to move.

[Mauna Kea Cloudforest]

Wouldn't that swale collect in winter rain water in larger quantities than wished? I am facing the same situation in my garden (slopy with orientation south-west), but truth is that native soil is clay with great water capacity and even greater in some points. So I feel bound to use a very porous medium to greater depth when digging holes for more tender palms. But I never make a swale in those cases because of the above reason. So far I had no problems with the porosity of soil in summer or the lack of large bowls, since irrigation water penetrates faster this porous layer and in fact I use more water for such outplanted palms. If I need to keep also surface moist in summer I better use mulch in form of pine bark combined with pumice as surface material (our pumice has the ability to absorb moisture and release it slowly) . As for the slope either I make a terrace (that is kinda a mound on the lower side of the hole), which is supported by bricks and stones (fig 1,2,3), plus excavated native soil and all those materials (stone, bricks, native soil) offer some insulation against heating soil. Or I take care that the side of hole downhills is on the same level with native soil, and in latter way soil temps maybe will be more independant from external elements. Last method I applied experimentally on an outplanted Thrinax (fig 4 and 5) with good so far results. But eitherway excessive rain water is allowed to flow downwards freely. I your particular case however intial situation seems reversed, since native soil is supposed to be fast draining and good warmth conductor. Maybe you follow second of the describe methods plus mulch in summer. If I have understood wrongly your problem I will be very glad to read more details from you.

I have very different conditions from yours. In our area, the rainforest (redwoods, ferns etc) grows on a mat that usually sits on top of sandy soil. My garden is much the same way, it's a mat of sandy loam and roots sitting on top of pure sand. The loam is about 5-7 feet deep depending on the location. If you make a hole, it drains very, very fast. There is no way I am going to plant on mounds. My hillside is already a giant mound.

Axel, why don't you plant them with the tillering direction perpendicular to the slope? (Like the contour lines on a topographic map) Remember that the 'heel' point remains fixed, and the enlarging diameter of the stem moves away from the heel. Thus it is easy to determine the direction the palm wants to move.

Now that's a stroke of genius! But isn't the tillering direction determined by both gravity and the heel? So isn't it impossible to get the palm to till in any other direction but down?

[Kostas]

Yes,palms heel according to gravity and change the angle of the heel according to it so that they go deeper. But,because they also move a little sideways as they do so,its very probable they will end up a little shallower that way than if they grow towards the hill. I would thinks they would be more stable if they grow towards the hill and deeper though,the angle of the ground makes for even faster drainage so the chance of rot of an underground growing point even if deeper,is quite low. I always plant my palms with the growing point at its original depth and thus for example,my Bismarckia's growing point is 30cm below soil level(remote germinator,sent a really deep cotyledonary petiole that split 30cm down),in flat ground on the plains, with clay soil around and the soil used for filling the planting hole a mix of peaty soil/compost/sand and 1/3 native clay. Moreover,the water table is very shallow and this winter i found water digging to just 30cm below soil level. My Bismarckia is fine and growing and it has been fine all of its years in the ground, from when i planted it as a germinated seed to now thats its 1,5m tall...So dont be afraid for your palm's health when they burry their growing point deep down Its good to not place the drippers right next to the trunk though but more than 20cm away as they grow as there is no point in keeping the underground leaf bases or trunk continuously moist when irrigating. The palms have much wider root system than that anyway.

[Phoenikakias]

Maybe I have not made myself clear enough. I did not say to plant on a mound, but rather to plant on natural soil level (or on wider swale's level) with an additional hole filled with pumice and deep to the estimated length of the stem lying underground and wide to the estimated final trunk diameter. I guarantee you will never experience trunk rot problems.

[Darold Petty]

Since gravity is fairly uniform over the surface of the earth I don't see relevance to this discussion.

The enlarging diameter of the stem moves laterally away from the heel point. Don't try to outsmart Mother Nature and millions of years of evolution. No one in Magdagascar excavates the soil level around wild Dypsis as the enlarging stem burrows deeper below the original level. Read this http://www.palmtalk.org/forum/index.php?/topic/33158-saxophone-axis/?hl=saxophone

[Mauna Kea Cloudforest]

Darold, i think I get it now. Having looked at enough heeled palms I get the fact that the palm moves away from the heel and down. It would then make sense to plant the palm in such a way that the heel is uphill and the palm grows away from the heel. That way, even though it's growing down, it's actually pushing itself down the hill at the same time, so the sinking trunk is actually not a problem at all. Besides, it looks better since the palm will have slight curvature at the base going away from the heel.

Now which species are considered to have high heels?

Since gravity is fairly uniform over the surface of the earth I don't see relevance to this discussion.

The enlarging diameter of the stem moves laterally away from the heel point. Don't try to outsmart Mother Nature and millions of years of evolution. No one in Magdagascar excavates the soil level around wild Dypsis as the enlarging stem burrows deeper below the original level. Read this http://www.palmtalk.org/forum/index.php?/topic/33158-saxophone-axis/?hl=saxophone

[MattyB]

I have a south facing slope, rocky soil, that dries out very fast. I have to make a watering basin like you guys have described above. I've been planting my Dypsis decipiens with the heal on the upslope side to avoid the growing point burying itself too deep. Like you said, it sorta just creeps down the hillside. I find that every couple of years I need to rework and make bigger the little rock retaining walls that make up the watering basin and make sure that the growing point is not buried in the dirt. Also, I have to mulch the watering basin in order to prevent it from drying out too much. Hope that helps.