Growing large numbers of palm seedlings economically
This was originally posted on the Trebrown forums in 2006. The thread is now closed. However, you’re welcome to leave a comment on this blog.
"I have large quantities of Phoenix sylvestris, Phoenix loureiri var. humilis, and Phoenix reclinata. I would prefer to avoid planting each seed into individual pots, as this would be very costly and time consuming on my part, so I’d like to grow them directly in the soil. Would it be possible to sow them directly into the soil, or should I try the ‘baggie’ method and then transplant directly into the ground when I see signs of root growth? Would either of those give good results? I’ve already got some Phoenix canariensis in baggies that have sprouted, and I’ve put half of them in pots – the other half are still in the bag as I’m wondering if I shouldn’t just stick the rest in the ground. Any help with this would be appreciated."
Well! I guess the first question should be; Where are you? If you’re in a reasonably warm climate then you stand a good chance of germinating them in the ground. Phoenix generally germinate better when planted in pots rather than by using the poly bag method. They need quite a bit of moisture, which when given to them in the bag tends to rot them faster. They need heat. Around 30°C (90°F) you might get away with about 25°C but germination will be slower and you may have some losses. So if you can maintain these temperatures in the ground then they will germinate. They are not too fussy about soil types. The main problem you’ll have by planting them directly into the ground will be losses through animals eating them.
"Thanks so much for your reply. I live in the US in North Florida – some sources say US zone 9a, others say zone 8b. It’s pretty warm here (averaging mid 70’s to low 80’s F, with evening temperatures in the high 50’s to low 60’s right now). I would assume it’s not warm enough to get them to germinate directly in the ground right now? Perhaps sow them in flats and transplant into the ground when they show signs of growth? My soil is quite sandy and somewhat dry, which would make germination even more difficult I’d think, unless I were to amend the soil where I’d plant. I’m primarily concerned with having to place them all into pots, as with the amount of seeds I’ve got, it would prove to be very costly and time consuming on my part. Jason."
Hi Jason! Yes! You’re better off planting them in pots. But not flats though! Especially the P. silvestris. You’ll find that these will send down radicals to about 12" to 18" from the outset. That will make it very difficult to prise the roots out later. The best way to handle Phoenix on a mass scale is to plant them in very deep communal pots. Get a deep pot and place a piece of fabric over the holes in the bottom. Then fill the pot ¾ full with a coarse sand or grit about 4mm. Then the last quarter fill with compost. Throw the seeds on top. They can completely cover the surface and be piled two seeds high. Then cover with about 1" of compost. Place the pot on a hotbed about 90°F, water well and cover with plastic. Depending on the species, the seeds will germinate on mass in about 1 or 2 months. Water regularly (being such a well drained medium, you’ll need to water daily). After about a year in that pot there will be a mass of roots. But not to worry about that, the roots will easily lift out of the coarse sand with minimal damage. You might want to place a few stones on top of the seeds to hold them down and force the roots through the sand. They have a tendency to push themselves right out of the pots.
"Your technique for starting them sounds really good to me – I will try it that way and definitely report back with how it worked out! You’re sure that it’s a good idea to leave them in the pots like that for a year though? Will they not set out leaves after a couple months? That’d be quite a tangled mess I would think, but at least it gives me some time to figure out if I should then pot them up individually or just plant them in rows in the ground. What say you? Anyhow, thanks a ton for your advice – it’s much appreciated!"
Jason I raise 10s of thousands of Phoenix seedlings every year! There is no other way to do this more effectively. There will be a lot of roots, but if you have a deep enough pot the roots will be mainly straight. I didn’t mean to say ‘lift them out’ in the last thread. I’m just used to saying that. You can’t pull them out. You tip the pot on it’s side and gently pull the plants. The sand will just fall off the roots. The longer (up to about 24 months) you leave them alone the less plants you will loose through transplant shock.
One thing I ought to mention is feeding! For the first year and part of the second the plants take all of their food from the seed. After that time they will require feeding on a regular basis, because the sand holds nothing for them. It is usually better to lift them after the first year. Even young (two year) seedlings would get eaten if you transfer them to the ground. You would be better off potting them on. Despite what some people say about under potting palms, Phoenix like over potting in deep pots, and plenty of water during the growing months.
I’ve had people ask about the method of growing palms in communal pots. So here is an example of the best way to handle Phoenix palm seedlings on a mass scale – Plant them in very deep communal pots. Get a deep pot and place a piece of fabric over the holes in the bottom. Then fill the pot ¾ full with a coarse sand or grit about 4mm. Then the last quarter fill with compost. Throw the seeds on top. They can completely cover the surface and be piled two seeds high. Then cover with about 1" of compost. Place the pot on a hotbed about 90°F, water well and cover with plastic. Depending on the species, the seeds will germinate on mass in about 1 or 2 months. Water regularly (being such a well drained medium, you’ll need to water daily). After about a year in that pot there will be a mass of roots. But not to worry about that, the roots will easily lift out of the coarse sand with minimal damage. You might want to place a few stones on top of the seeds to hold them down and force the roots through the sand. They have a tendency to push themselves right out of the pots. Adriaan asked:
a) For which species can I use this method of (mass) planting?
b) How deep should the pots be to give the roots plenty of space for growing in a straight line down?
To answer the second question first; Always as deep as possible! This depends on the species, some species produce very long roots from the outset, up to 60cm (2 feet) long. Others produce much shorter roots. You need to know what the species you’re growing requires. But It’s generally better to provide a deeper soil than you need. The answer to the first question is much more general; I grow most species of palm using similar methods, but not all. Some species, and I’ll use Bismarckia nobilis as an example ought to be planted individually in their own deep pots, because deep rooting species like this don’t like having their roots disturbed. But for most other species; they get planted in my nursery in one of two ways; The one I’ve already mentioned, using a lot of sand, and for species with a more tropical requirement, and where they require better water retention in the soil I use only ¼ of sand in the bottom of the pot with the rest of the pot filled with compost. With Phoenix and several other species; The seeds can be sown directly into the pots. But most species of palm require some kind of pre-sprouting method like the ‘baggie’ method with applied heat.
"Thanks for you answer. But, when I use this method, is there no problem with the small leaves? Example; Trachycarpus fortunei will make some wide leaves, is the space for the leaves no problem? And a pot of 60cm deep? That’s almost impossible to handle. Can you give some more specific depths for some species like : Cycas revoluta, Wodyetia bifurcata, Dictosperma album, Trachycarpus fortunei, Phoenix canariensis, Phoenix loureiri var humilis, Phoenix roebelinii, Roystonea regia, Ravenea rivularis, Chamaerops humilis, Archontophoenix alexandrae, Hyophorbe lagenicaulis, Hyophorbe verschaffeltii, Pachipodium lamerei and the Pritchardia thurstoni? I hope you can give 1 or 2 depths which I can use for most species. And I assume that this method wont work with cycas revoluta and wodyetia bifurcata seeds, or do you think that will work also? Thanks Adriaan."
Hi Adriaan. That’s a lot of questions for one thread! The first bit about the leaves; I don’t really understand! Palms being Monocots start life by producing a single strap leaf. They will produce about five strap leafs before they start producing their true leafs. In the first year (depending on species) they will only produce 3 or 4 leafs. The mass planted seedlings look like grass growing in the pot. Yes! Deep pots are always hard to find. But if you’re growing on a really large scale you can use large bins. On a smaller scale, try using specialist palm pots or rose pots. It’s not too expensive to fill these pots because you’re using mainly sand. Wodyetia bifurcata does very well in communal pots. But I grow my Cycads in individual pots. I know some people do grow Cycads in communal pots. I won’t answer your question here for all the different species you mentioned. It would get too long! But one I ought to mention is Ravenea rivularis. I grow these in communal pots with a lot of sand, but these really need a lot of water, so you must remember to keep watering them. For the other species; you need to think of their requirements. Are they deep rooting species (radicle forming)? or are they shallow rooting species? Do they require a very well drained soil or do they require a good water retaining soil? These answers can be found in books about the individual species or you can ask here about a particular species. But I generally give each species a few cm deeper soil then they will use.
"What is best method of mixing your own potting soil for: A) sowing seeds and B) replanting palm seedlings? I live in the Caribbean (hot climate all year. What should I include to make the seedling grow healthy and good? Please include quantities for your suggestions. Hamilton."
Hamilton, I make all my own seed and potting mixes. For many palm types the seed mix should not contain any loam (garden soil) for some it is OK but I don’t for any palm seeds. The best seed mix is simply 50% peat or cocofibre and 50% course sand. That works well for most palms, but I make a 70% peat to 30% sand mix for some of the more tropical and water requiring palms. For potting on it’s more complex, but I try to replicate the natural environment’s soil from the origins of the palm as much as possible. A potting mix should be rich in all trace elements and as deep as possible.
If you live in the USA there are a couple of manufacturers of very deep pots. Namely, Steuwe and Anderson Die. I have considered importing these into the UK before, however I’m still not sure if the extra cost is justifiable. Deep rooted palms do pose a real problem, because a relatively small plant requires an exceptionally deep pot, and if you were to use an oversized pot for these it over inflates the cost of the plant commercially. Flower buckets make excellent communal pots for sprouting palm seeds on mass. We use plastic fish boxes or other similar boxes commercially for this purpose. But this doesn’t provide an answer for potting individual palms. Although the flower buckets are suitable for some of the larger species. For potting on we have taken to using the black expandable gusset polythene pots that were popular a decade or more ago in the nursery trade. The commercial sizes are not suitable so we have these manufactured to our specifications. I.e. we have the standard commercial sizes but we add 2 to 3 times the height to the pot. The drawback is that expanding palm roots will soon split the bags. But we use that as an advantage and plant the bag with the plant in larger pots as and when needed. This aids the plant by minimising root disturbance during re-potting. These expandable gusset pots also offer a number of other advantages i.e. the much cheaper cost, and you can cram a lot more plants on to a single growing bench allowing minimal run off of liquid fertiliser.
I can only think of one instance where one would plant seeds direct into the poly pots. That is for Jubaea. Those seeds are sprouted first then planted in 1-litre narrow poly pots which are filled only with sand. The sand prevents rotting which so often happens with Jubaea, and of course seedlings don’t require any nutrients in the soil, as they get all that they need from the seed. As soon as the roots start breaking through they are potted on, bag and all in a proper growing medium. I suppose you could do the same with Brahea, Bismarckia, Borassus, Attalea, Butia, Corypha, Hyphaene and many more of the exceptionally deep radicle forming species. We don’t though; we plant all the higher value deep rooting species direct into their own rigid pots from the outset. Butia are communally planted. The gusseted poly bags are used almost exclusively for potting-on until a deep rigid pot is justified.
"When can I move my seedlings outside?
I now have various palm seedlings in pots on windows sills and in propagators around the house from seeds I bought from you. Now that I have bought a greenhouse, would you be able to advise at what time of year I could bring some of these outside into the greenhouse. I have all sorts from individual Euterpe edulis pots to communal pots of 100’s of Washintonia (looks like grass) Also, does a greenhouse speed up the growing process? As you advised in another thread seedlings grow about 4 strap leaves per year and I just wondered what helps this speed up; i.e. direct light from a lamp on the plants when in the house in the winter? Thank you Douglas."
Hi Douglas, It’s the number of Growing Degree Days (GDD) in the year that will make your palms put on the most growth. So obviously you’ll maintain those temperatures better indoors or under glass than you will outdoors. Your glasshouse may not be as warm as your house at this time of year, so you’re better at making the decision when to move them. Your glasshouse will maintain better light and humidity than your house though, and your palms will welcome that. Your potting on from the communal pots is very much different for each species. At most you would only want to leave them communal for 2 years. But the Washingtonia and Euterpe are very fast growers and you should over pot these now, feed them well and stand back and watch them grow, both require a lot of water during the growing months.
"Thanks for your response Phil. Does that mean each individual strap leaf plant needs to go in its own pot or could I just take the rose pot I’ve got 100’s in and pot into an even bigger pot? Thank you Douglas."
Hi Douglas, If the plants are too crowded then they will self thin themselves out until only the one strongest plant remains. They not only need to be potted up individually, but they need to be done with care not to damage the roots, and they’ll need very deep, over sized pots. If you’ve followed my advice from above then you will have planted those Washingtonia communally in very deep pots or boxes. In the bottom half of the pot would have been course sand. Now when you gently lift the seedlings out you will find that the sand falls off the roots, and with a little gentle prying you will be able to separate all the seedlings without damaging any of the roots. When a palm root gets damaged, then that root will die back to the base of the stem, where a new root will grow to replace it. If you damage all the roots (and there are probably only 2 roots per seedling) then the plant has no roots, and will die before it has chance to put out any more. Palm roots are not like other tree roots. You can’t prune them in the hope of making them bush up. This is the same for mature palm trees. If you want to transplant a mature palm you should dig around the tree one year, then return the second year to under cut. This will permit new root growth around the surface of the soil from the first lot of damage, and mean that the tree has a new set of roots to carry it through the transplant. You must find the deepest pots you can find for your Washingtonias. The same is true for all desert palms. These send down long roots through the sand in search of water, and you need to accommodate these roots as best you can. And despite what I’ve heard some people say, Washingtonia will grow very very fast if they’re over potted in large pots, well fed, and given plenty of water during the growing months.