Tropical Gardening: "Found" Plants

"Anything you stick in the ground grows..." 

Updated 12/01/2020

Not quite in my backyard.  The soil is very mineral rich but, particularly in my part of Oahu due to the long history of plantation agriculture prior to large scale residential development, often lacking an organic layer.  Which makes water retention and root growth difficult.  However, many things will grow if you start them in some nice potting soil in a pot, and then plant them out with the full pot of potting soil once they are established.  There is the wonderful ability to plant out your expired / used produce to make more.  Much much much more.

Coconut, Cocos nucifera

Monkey's Bellow's Beach Coconut

Bellows Beach is East facing and lots of interesting things, and tons of plastic, wash up when the winds and tides are high.  Monkey always brings treasures home for his collection and Monday sharing at school.  One day he managed to sneak a coconut the size of my head into our beach basket and for the rest of the week I kept putting it in the garden and he kept putting it back in the kids' room.  Squiggles started ratting him out as soon as he came in the house with it.  I finally told him to find an interesting place to put his "found art" in the garden and we would treat it like yard sculpture.  A month later it had sprouted. And in May it was as tall as Monkey.  Interesting thing about coconuts, you can plant them sideways and they'll happily grow.  You don't even have to plant them and they'll grow.  But if you plant them sideways they grow into a nice bench before they turn upright, which also lowers the top of the palm relative to the ground and makes nut collecting much easier and potentially less lethal.

According to several blogs  coconut palms can be kept in a pot the size ours originally inhabited(2nd and 3rd image) for up to 5 years   https://www.gardeningknowhow.com/edible/fruits/coconut/growing-coconut-palm-trees.htm    They have roots like grasses, shallow grasses not North American prairie grasses https://www.hunker.com/13428751/coconut-palm-tree-root-facts. And they are very sensitive to chemicals, particularly noted is concrete, with specific instructions not to plant near paving. Which makes me wonder how far from the cinder block wall I would have to plant it. 

However if you look at the 4th image,  I repotted it into a bigger pot because the tap root, yes there apparently is one at least on whatever variety we are growing, had come out the drainage hole in the bottom of the original pot.  I had to tug it out, but it survived repotting and a slight root skinning.  So now it is in a HUGE pot, and planted sideways with the top facing the afternoon sun.  I would have it completely facing the axis of the sun, but that is downhill on its gravel pile and it would tip over.  Yes, yes I should plant it in the ground now, but we are renting and I really want the coconut to come with us when we finally get our forever home.  

Pineapple, Ananas comosus

Dean Pineapple Plantation

 Ever since reading Richard Langer's The After-Dinner Gardening Book, I have known I could start pineapples from the cut off tops.  Supposedly it takes 3-5 years for the plant to mature and produce another pineapple.  This is the second pineapple we've had off this particular top and we've had it only 3 years.  The plant will then grow more, smaller pineapples from side shoots.  Then you can also start another pineapple from the top of the one you have just harvested.  Basically one pineapple puts you in an ever increasing, though perhaps smaller sized, supply of fresh pineapple every 2-3 years.  We have a dehydrator and dried pineapple is one of our favorite "candies".  You will notice the potted plants are greener and bigger, though much younger, than the plants in the ground.  This may be as much due to the pots being in the shade usually as it is to the soil quality. Update: I replanted almost all of the in-ground pineapple to shadier locales and they greened up and grew bigger leaves, so my personal recommendation in USDA zones 12 and higher is to put your pineapple in dappled partial shade.

Update 8/6/2023: a master gardener at the Mililani Garden Club told me her pineapple are stacked on top of each other against a wall and grown as air plants. I am intrigued and asked to see photos. 

Lemongrass, Cymbopogon spp.

Lemongrass from 2 dried out sprigs from the pre-cut "herb" package in the produce section.

Lemongrass is invasive in Hawaii, honestly everything is invasive in Hawaii.  But I love it and it is rumored to repel mosquitos.  Plus we're cooking a lot of tropical region soups and sauces that use it and it is weirdly expensive here. So I soaked the saddest of the sprigs from that particular grocery purchase in water until I got the tiniest of roots and then I stuck them in a pot and several months later I had to repot them in individual pots.  Both already have little vegetative babies so unless I suffer plant catastrophe, I don't have to buy anymore lemongrass.  Update: I ended up with 4 huge overcrowded pots from a later division of those original 2 pots and have been planting sprigs all over the yard. Update of the update: when cutting lemongrass stalks for use, take the older central stalks as close to the ground as possible.  The surrounding stalks will fill in the gap within a month.  Ground-grown lemongrass, on Oahu at least, has a pretty purple base to the stalks.

Ginger, Galangal, Turmeric, Zingiber officinale, Alpinia galanga, Curcuma longa

Ginger (skinny leaves left and middle) and Turmeric (bigger rounder leaves, right), Galangal has huge roots (far right)

Zingiberales thrive in Hawaii.  The Polynesians brought turmeric and shampoo ginger with them.  All the turmeric and ginger I have found in the stores here are locally grown and huge.  The ginger is also pink tinged, juicier, and just absolutely amazing.  Buy one package of each.  Plant a couple in the shade.  I planted a whole pack of each and we have ginger and turmeric everywhere.  Super excited for home grown Indian food.  Galangal is another Zingiberales that does well in a Hawaiian garden.  We ordered some online for a Thai stir fry and had 3 chunks leftover.  One rotted in the pot but the other 2 survived and filled out the pot in several months.  I have since learned galangal in the ground can reach 7 feet tall and the roots are ridiculous when grown in a pot.  So I have been planting it out along the wall to provide some shade or at least reduce the light reflected into the house.  I am excited to see what the flowers look like.  August updates galangal has not flowered yet but I've had to repot it three times and planted it all over the yard.  The turmeric and ginger produce wonderfully fragrant white flowers that are much prettier than the ornamental gingers (which aren’t Zingiberales at all).

Sweet Potato, Ipomoea batatas

Sweet Potato, planted by previous residents

The sweet potato was already in the yard, but you can grow your own slips from purchased tubers.  Richard Langer's The After-Dinner Gardening Book covers this also.  I've been digging up tiny ones from the yard and transplanting them in pots, then trimming the stems and rooting those.  Interestingly I get different colored tubers from the same original plant.  These tubers, whatever variety they are, are smaller than mainland grocery store sweet potatoes.  They do really well in window boxes.  I want to try them fried whole like fat french fries, as a side to that awesome ginger turmeric lemongrass curry I'm gonna make.

Green onions, Allium fistulosum

Spring onions from the trimmed roots do really well and now we have several pots and many in the ground.  They do well in moist shade here.  I had used cinder blocks as an edging to expand some beds under existing landscaping on the south side of the backyard to plant some turmeric, ginger, galangal, and pineapple in the shade, edging the beds with spare cinder blocks from the yard.  The onions seem to do quite well when divided and planted individually in the cinder block holes.   When they flower and set seed I pinch off the tops and put them in a fresh pot.  Hubby wanders outside with the kitchen shears at least once a day and adds fresh green onion to something: omelettes, curries, tacos, baked potatoes...  

Mango, Mangifera indica

In 2020 we subscribed to Oahu Fresh and received weekly grocery bags of very fresh locally grown produce.  Produce so fresh, the seeds sprout when the kids tuck them into gaps in the yard or the plant pots.  I knew mangos could be sprouted from seed because of yet another entry in Richard Langer's The After-Dinner Gardening Book.  I did not expect ALL of the seeds the kids popped into pots to sprout.  So now we have 5 mango, the original Mele Kalikimaka tree which is a self-pollinating clone grafted onto hardy root stock, and 4 wild unknown sprouts which are of course growing much more vigorously than their cultivated cousin.  I also gave 2 wilding mango away with warnings that they might not reproduce on their own or at all.

Mango can be 80+ foot tall trees, with dense wide canopies.  Or you can prune them into whatever you want, including really fat stemmed espalier on a super sturdy frame.  In Japan they are grown in greenhouses, pruned short, with huge side branches propped on wooden frames.  The individual fruit are wrapped while still on the tree to ensure unblemished perfection, and the fruit sell for $30 or more each.  

When I repotted the wildlings, the largest tree broke off its' seed.  I was sure it was a goner, the crown wilted, turned brown, and fell off.  Nope, the shoot has grown 2 inches past the remaining leaves and started sprouting again.

https://www.hawaii.com/discover/mango/ 

Avocado, Persea americana

https://www.ctahr.hawaii.edu/oc/freepubs/pdf/C1-382.pdf

Grew one from a pit, first time trying.  Apparently do not like heavy pruning.  Keeping them small and manageable requires constant vigilance with a light pruning hand. They are not evergreen and will shed most of their leaves whenever the weather dries out. Which can be alarming when you come back from a two week vacation and you think your avocado died. It will most likely leaf out again. 

Rambutan, Nephelium lappaceum

This was a complete surprise.  I was familiar with lychee from Asian markets in New Jersey, New York and the greater Washington, DC metro area, but had never seen the related rambutan before and certainly did not know they grew on Oahu.  I prefer the rambutan.  We received 5 in an Oahu Fresh delivery.  The kids shrieked in horror at their spiky red appearance, then Hubby whipped open his knife and flipped the white fruit out of its surprisingly flexible skin that now looked like funny helmets (which the dolls wore briefly) and they disappeared instantly into happy mouths.  The five seeds were poked into a pot that was supposed to be germinating a Ylang Ylang vine.  A week later we had multiple sprouts in the pot and many more Rambutan in the delivery.  Seeds went in another pot.  Then Hubby bought a large bag of them at the grocery store and I had 6 pots stuffed with seeds.  All of the rambutan we have found so far on Oahu are the red variety (there are also yellow and green), but no idea which cultivar(s).  

The seeds are viable for about a week after consumption of the flesh.  They sprout very oddly, some have single shoots others have multiple shoots, some of the seeds turned green and broke up into several nubbly pieces which have sprouted individually.  This is another tropical fruit tree that can grow up to 8 feet or more and may not be self fertile (though most are) - actually I am finding conflicting information on this point.  Purdue University Horticulture Department  states the male to female ratio is 2:1, so I guess I'll plant in groups of 3.  However, like the guava and the mango does well with heavy pruning and can be maintained at 3 meters tall and wide.

Mangosteen, Garcinia mangostana

This was a surprise which I had never had before, and may never have, had 3 not shown up in an Oahu Fresh delivery a couple weeks ago.  I ate all of them.  No one else wanted them which was silly because they are wonderful.  Apparently a delicacy in south Asian countries.  I got one seed from each and planted them all.  Nothing yet. Which may be because they have to be planted 8 inches deep in a deep pot and take 20 days to germinate.

I am excited by this one because the peels are used as a purplish red dye, and it is grown as a shade / understory tree and can go between the avocado and the mango in my food forest.

Alas they did not sprout and i have had none since.