This section is from the book "The Florists' Manual", by William Scott. Also available from Amazon: The Florist's Manual.
I have within a few years heard of several of our leading palms being planted out in spring on a bench in six inches of soil and grown there during the summer and lifted in the fall. You can doubtless with great heat and moisture produce a latania or a kentia much larger in the same space of time that you would be growing it in a pot, but would it be as serviceable a plant in the fall? Would you not have to lift it early and get it well established before you sent it out to the confiding retailer? We don't believe it is a good plan and would not buy such plants if we were aware of it.
Producing a large, showy palm is not the only object. People who give you a good price for a 6-inch kentia or latania expect it to thrive in the house a few weeks at least, and the plaintive cry of " My palm is turning yellow" has robbed us of most of our hair, and we don't want to hear it. They must die sometime, it's true, when growing or existing in the house, but let them pass gradually away, fading away slowly, and then their demise will be taken by all hands as complacently as the departure of an elderly wealthy aunt.
Palms thrive in a small pot compared to the size of plant, and should not be given a large shift at once. Growers of large quantities shift on as the plants need it at any time of year, but the florist who keeps only a few hundred had better do his shifting in the months of March and April, when there is a constantly increasing temperature. Always pot firmly. Up to a 5-inch or 6-inch size this can be done by squeezing the soil with your fingers, but in large size, and particularly if the shift is small, a blunt stick will help very much to firm the soil. Some writers say that roots never should be cut. Perhaps there is no need of it, but I have seen the roots of latanias and old seaforthias chopped off without doing any harm.
Never pot too deep. The base of the stem from where the roots begin is easily defined, and they should not be potted below that. Some species, ken-tia for one, raise the stems by the strong roots. When shifting, lower the plant to the base of the stem, but not lower. It is never advisable to shift a plant, say from a 6-inch to an 8-inch, just before selling it to your customer; far better let it go in the smaller pot and tell him it will do very well in that pot till spring; give it plenty of water. Palms do not seem particular about soil, and the mica so often seen in the potting soil used about Philadelphia appears to agree with them very well. I would consider the ideal soil or compost for palms to be a rather stiff yellow loam sod, cut and laid up in summer, and between every foot of the sod a layer of two inches of cow manure. When this is thoroughly soaked, and after a month or so, cut it down and chop over, and in a few weeks give it another turn. By that time the manure will have about disappeared, and the compost will grow any palm. A good supply of this should be under cover during winter for early spring use. If you cannot make these preparations, get a fresh loam and add a sixth of well decayed manure. Bone meal is often used with palms, and if a quick growth is desired it can be added to the compost at the rate of one pound to each bushel of the compost.