Potting Tips Page


This page contains information about repotting your begonias and related topics such as soil mixes, etc.


Repotting: Potting Up or Potting Down

by Brad Thompson



Well whether you pruned your plants last month or not, this month itís time to start repotting. Depending on how they fared the winter you will be potting up or potting them down. Remember not to repot plants that you just pruned (unless youíre absolutely sure you wonít overwater) but if you pruned earlier and you have good growth going, go ahead.

One comment Iíd like to make is that whenever I talk about watering less, I mean water less frequently, not give less water. You should always water plants thoroughly when watering so that water runs out the bottom of the pot. If you just give less water , the roots will die in the parts of the pot that stay dry. Iíll talk more about this in the potting down part.



In Drawing One: You can see your basic cane or shrub that youíve had for a few years with several old stumps from previous prunings. Your options are to just pot in a larger pot and hope for enough new growth to cover up the stumps, prune all the canes back to the soil line, or pot lower in a larger pot to cover the stumps up. The best option is the latter; you will get a lot of good basal growth and the old gnarly growth will be buried.




In Drawing Two: You can see what needs to be done to prepare the plant for potting lower in the new pot. If the new pot is taller than the pot you removed the plant from, you may not need to do anymore than loosen soil from the bottom of the plant with your hands. You should loosen a little soil from the sides too. If youíre going to repot into the same size pot or a pot about the same height you will have to slice some soil off the bottom of the plant, either with your hands or with a knife as in the drawing. Cut off plenty so that when you set it into its new pot, it will set low enough when soil is added on top so the stumps will be buried as in drawing three. Donít worry that youíre going to hurt the plant; pruning the roots will encourage new root growth. You may need to trim back the top of the plant also if you have to do a drastic root pruning. Again, just be careful not to keep the plant too wet.


In Drawing Three: You can see how the plant will be placed and how it will look in the new pot. Put a thin layer of new soil mix in the bottom of the pot first. Place the plant in the center of the pot (if the plant was originally way off center you can trim a little off the side of the root ball so it will be centered in the new pot) and pack soil mix firmly down the sides of the plant. continue filling and packing till the pot is full and the stumps are covered, leaving some space at the top for watering space. After repotting, water thoroughly 2 or 3 times to make sure the new soil gets wetted or you may end up with dry spots that wonít rewet.


In Drawing Four: You can see when you need to pot down. There are many ocasions when you may need to down-pot plants, especially plants that stayed too wet all winter. These are plants that may have been put in too large a pot to begin with or plants that you just love to water, or stayed out in too much rain. If you lift a plant gently out of its pot as in drawing four and most of the soil stays in the pot, it means the roots have died and there arenít any roots holding the soil together as in a healthy plant. If you pull on the remaining soil thatís on the plant you will see that it falls off easily too and you will see few or no healthy roots (healthy roots are whitish with lots of little root hairs on them.) You need to remove as much of that old soil as possible without damaging the plant and repot it in fresh soil in a pot slightly larger that the remaining rootball. If itís a large plant, you may need to remove some of the top also so the rerooting plant wonít have to support all that foliage.


I suppose I should mention something about soil mixes. I can only tell you about what I use, you will need to experiment to find what works best for your watering practices. The mix I use has been called Ronnieís Mix, Eldaís Mix, or Maryís Mix but will be referred to now as Bradís Mix. The ingredients are equal parts LGM planter mix, #2 perlite, LGM leaf mold and small orchid bark(1/8 to 1/4 inch size). This mix works well for me, itís light and porous (at least for the first year or so) and does grow begonias. There are many different types of begonia mixes and which type you need to use really depends on the area you live in and whatís available. Please donít send letters asking where to get LGM products, they are local, and I only gave you my mix as an example. Iím sure other brands will work the same. Also, Iím able to grow outdoors all year and this particular mix doesnít work well indoors. If you have other questions donít be afraid to write or call, Iíd love to hear from you...


Rhizomatous Begonias: The Way of Clay


by Brad Thompson

Over the past couple of years I have chronicled my endeavors to grow rhizomatous begonias successfully. Now, I will admit that I have never been a total failure, but my rhizomatous begonias never seemed to thrive like my canes and most took extreme measures at one time or another just to avoid losing the variety. For that reason, I have experimented over the last few years with varying methods to try and grow them more successfully on a consistent basis.

The closest that I came recently was when I tried putting a layer of large #3 perlite in the bottom of shallow plastic pots with just a thin layer of soil over that. I first started using that method a year ago last summer and saw much better results during the winter and spring than in previous years. I had pretty much decided that it was a resounding success until later that summer when they started looking bad, suddenly. Not every plant, but the majority were very unhappy. The conclusion that I came to, by the symptoms that the plants were display-ing, was that they were getting fertilizer or salt burn. Rudy Ziesenhenne has said that he stopped using perlite in his mix for that reason. What was happening, I believe, is that during the fall and winter of that year, when I wasnít fertilizing very much, the plants were fine. During the spring and summer when I was fertilizing a lot, plus the added salts in our water, was causing a fatal buildup of salts in the perlite. I knew this kind of a buildup was possible but didnít figure it would happen quite as fast as it did, (I figured that they would be fine until repotted the next year) Rudy had said they would have to be repotted every 2 or 3 years if you put perlite in the mix, so I figured I was safe since I repot nearly every year. An additional factor, is the fact that rhizomatous begonias donít seem to need as much fertilizer as the other types, which made matters worse.

Anyway to make a short story long, I have changed to the only growing method that has seemed to be tried and true for a number of years, which is to grow them in clay pots. I have never had a rhizomatous begonia that didnít thrive in a clay pot but since clay pots are more expensive, much heavier, and harder to maintain, I have tried valiantly to find a way to grow them well in plastic. To me, it was more important to have them grow and survive, than to worry about the additional work and expense. I have repotted almost all of my rhizomatous begonias into shallow clay pots. I got them reasonably cheaply at a pottery discount company and they really werenít that much more expensive than plastic, (some were cheaper, in fact).

Even though this was (late fall) really not the best time to repot anything, I felt it was necessary because most of the plants would probably not have survived the stresses of winter. Most showed a sudden burst of growth even though winter was coming. I used my regular mix and just moved them into the same size pot they were already in but used clay instead of plastic. Nearly all of those plants thrived last year so Iím going to stick with clay. Many of my friends have also switched to clay. Anyway, go with clay for rhizomatous if you havenít been successful with the plastic.


Potting Basics


by Brad Thompson

Regular repotting is very essential to the well-being of your begonias, especially in their first few years, as they are growing and maturing. Later, after the plants are mature and have already reached the maximum size you want them to be, you can let them go for a couple of years without repotting. Yearly repotting will still be beneficial. Even with plants that you intend to keep in the same sized pot, you need to change the soil to keep the plant growing vigorously because the elements of your soil mix do break down over time. It loses its draining qualities and its airspaces needed to hold oxygen. You have certainly noticed with plants you have repotted that the mix, especially in the bottom of the pot, has turned to fine mud. The following is a list of tips and procedures for repotting.

1. You should wait until a plant has filled its pot with roots before repotting. If you gently remove the plant from its pot, you will be able to tell if itís ready. If the plant holds all of the soil together then it is ready to be moved up. If there is still loose soil that stays in the pot after you pull the plant out, it needs more time. (pulling the plant out of the pot will not hurt it any.) If you have waited too long and the plant is root bound and the soil ball is totally filled with roots, then you should gently loosen it before repotting. Just a little reminder about potting down. If you pull the plant out and it doesnít have hardly any roots and most of the soil falls off, you may want to pot it into a new pot that fits the rootball to get it going again.

2. Selecting the pot: Donít pot up into too large of a pot or make too big a jump in size. Generally, only move up one pot size at a time, because itís better for the plant to be potted more frequently in smaller jumps than to make one big jump. An analogy would be, you could easily jump off a cliff if you did it in two foot jumps but if you did the whole hundred feet at once it would probably kill you (yes youíd be tired but you wouldnít be dead after 50 two foot jumps.) If you try moving a 4 inch plant up to an 8 inch pot in one jump thinking the plant will grow bigger and faster, you would probably have the opposite effect, if the plant lived at all. The problem with potting up too fast is not with the mix, itís a problem with the amount of water that will stay in the mix. A 4 inch plant canít use up the water in an 8 inch pot quickly enough. The soil stays too wet, sours, and starts killing what healthy roots the plant has. For small plants only move them up in 1 inch increments until you get to about 6 inch size, when you can make 2 inch jumps in size. Such as a 6 inch pot up to an 8, then an 8 up to a 10 etc. An additional note; when moving up the smaller plants you need to remember that moving from a 3 inch round pot (for example) to a 4 inch square pot is a much larger jump than moving up to a 4 inch round pot. Donít move up to the square that way unless your plant is very well rooted and has pretty good size. Even then be careful with the watering.

3. Your potting mix: Many of you have your own potting mixes, and if what you are using is giving you good results then keep using it. Mixes work differently depending on the growing conditions and your watering practices. I have experimented with various mixes over the years and have found that the only mix that works perfectly for me is the mix that most of our members use. The reason it works well for me is that; its very porous and allows water to drain well, it has enough organic matter in it to counteract my alkaline water as it breaks down, and my plants like it and grow strong healthy roots. I have tried other mixes based on Supersoil, Unigrow, and Bandini and some other commercial mixes but none of them really worked well for me. Some commercial mixes contain sawdust, which binds up the nitrogen in the soil, so your fertilizer doesnít work properly and some stay either too wet or too dry, to work well for begonias. Even when mixed with other amendments such as perlite, leafmold, etc. they just didnít seem to work as well as the mix I use now. Some growers also use peat or peat based mixes. They may work well if you live where you have to water frequently because of extreme heat in the summer. Peat mixes are very hard to keep wet if they ever dry out completely. If you ever buy a plant that is planted in peat or a mix that is very different from the one you use, remove as much of the original soil as you can and repot it in your own mix. If you leave the old mix, especially peat moss, it can dry out later in the middle of your pot and not rewet with normal watering. You wonít even know until the plant starts to suffer. Iíve had plants that I left the peat soil on and planted them in baskets and they always seemed to be wilted looking even though they had just been watered. When they were removed from their pots, I found that the couple of inches of fresh soil were fine but I had a large brick of dried peat moss in the middle that was as hard as a rock. When I watered, the water just ran around the dry middle and out the bottom, so the middle never got wet. You can see itís important that whatever mix you use, the plant always stays in that same mix. If you change to another mix remove most of the old mix first.

4. When repotting, except for rhizomatous and tuberous, try to plant the begonia deeper than it was planted before. This is especially important if you have old stumps at the base of your plant from previous prunings. This will give your plant a fresh new look and also cause new bottom growth and new roots to form. If necessary, especially if you want to keep it in the same size pot, remove enough soil from the bottom of the plant so it can set low enough to cover up those stumps. Make sure to allow for at least a thin layer of new soil in the bottom of the new pot.

5. Filling with mix: There are differing opinions on this point but Iíll give you mine of course. I like to firmly pack the new soil around the plant. The reason I do this is; to remove large air pockets which will fill with water, to make sure the plant is in good contact with the new mix, and so the new mix will stay the same wetness as the old mix. If you only fill around the soil ball loosely, when you water later, the water will flow too easily through the looser outside mix and may not wet the soil ball evenly. Some feel that if you pack the soil down you damage the roots too much but I havenít found that to be the case in the hundreds of plants that I have repotted that way.

6. Fertilizing when repotting: When I repot my plants, I always give them a fresh dose of slow release fertilizer, such as Nutricote (TM) or Osmocote (TM). This makes up for any times that I miss my regular fertilizing (which I use in addition to Nutricote) and especially keeps all of my plants that I grow around the front of my house fertilized. I never make it out there with my liquid fertilizer, so thatís usually the only fertilizer they get all year. Repotting is the easiest time to apply the slow release because you know they need it then. If you consistently use the slow release for every plant you repot (except for your rhizomatous begonias which may be burned by surface applied slow release fertilizer) then you wonít miss any. Follow the directions on the box for amounts and how to apply, with any fertilizer you use.

Hopefully this article will help remove any questions and doubts you have about repotting and will help you get a good start this year. I know there are probably some things I didnít cover. E-mail me if you know of something I left out or other questions you might have.


Potting Mix: Getting the Dirt on Begonias
By Tim Anderson

One of the most popular topics of conversation among a group of Begonia people is, ďWhat do you put in your potting mix?Ē or ďWhat mix do you use?Ē Since Begonias, for the most part are not very particular about what they grow in... What? You say, ďThey are particular?Ē OK, OK, but in the wild begonias can be found growing almost anywhere where there is moisture with constant humidity, during at least one season of the year. Does this mean then that we canít grow all types of begonias in one basic potting media. No, you can.

There are four elements that should be provided for a plant by a soil mix:

(1) Something to hold on to, an anchor, a comfortable place to grow where the wind will not make a tumble weed out of the plant.

(2.) A water reservoir, like a sponge, storage for as long as possible as much water as possible.

(3) Nutrients, (I use a refrigerator and cupboard to store mine.) A soil needs something also to store food for the plant. ďA soil should have good Ďaeration exchange capacity,Ē a soil scientist would say.

(4.) A soil should provide access to air or nutrient gases. Oxygen is good, I particularly like it, but the plants like carbon dioxide better. The nutrient gasses in the air are as important as NPK (Nitrogen, Phosphor-ous and Potassium), the three most famous soil provided nutrients.

As long as we mix something up that provides these four requirements to our little charges, they should be most grateful. (Forget about air movement, temperature and light for the moment.)

Letís examine these 4 requirements:

(1.) A place to grow. We start with a pot, or suitable container, into which we will put something heavy enough to hold our little beauties up so the slightest breeze will not knock them over. The best source of weight in this case, is a good grade of horticultural sand, a sharp sand, a coarse sand, usually a silica sand. As opposed to a round grain sand that acts like quicksand that as itís wetted will not allow air to move properly. Since the roots of plants need as much air as the top of the plant, this cannot be allowed. A good sand, by itself, sounds like a complete media for our Begonia plants. Well, yes, it almost could be, but... a 6Ē pot would weigh a ton and the ability of sand to store plant food is not the best.

(2.) We add a water storage element. Peat moss is the material of common choice. A good leaf mold, a good organic compost, the new coconut peats et. al., can and will do the job. Like a sponge they will hold water and nutrients. For hundreds of years peat moss and sand has been the most common Ďsoil mudí in container use.

(3.) Now letís fill the refrigerator and cupboard with nutrients for our plants, or Ďfertilizerí. The most common choice is fast food, such as a water soluble fertilizer. Fast food does not store well, as you know. The next type is slow release materials. These are the canned foods of horticulture. They store longer and have made life easier and are always ready. Homemade foods. when done correctly are the best. This would be the use of things like bone meal, fish meal, alfalfa tea, etc. This is the media of the true Ďartí of horticulture and one must be a true Ďgourmet cookí to use them successfully. Thankfully, we have access to these other prepared foods that will satisfy the plants nutritional requirements

(4.) Last but not least, the most important of all, we must supply both the top and bottom of the plant with copious amounts of air. The top of the plant is always in the air, but the roots, must also have air. A really good mix of coarse sand and coarse peat moss can allow air to move in the roots. Peatmoss decomposes and as it does it will eventually block air movement around the roots. To keep the air spaces open a coarse material is usually added such as: ground tree bark, gravel and styrene beads. (Notice we did not say perlite, with good reason, which is yet another story.) Lastly, we put a drainage system in our containers to facilitate drainage and to ensure good root access to air. This is done with course gravel, broken pot shards, etc. The newest and best is to recycle plastic shipping peanuts. This article maybe be somewhat over simplified, but I hope this will give a new slant on an old topic. Enough rambling I have to go pot!

(Tim Anderson writes about and grows begonias in Miami, Florida where he runs Paul Hammock Orchid Estates. They specialize in Rhizomatous, Cane, Rex and miniature Begonias. They also carry Orchids, Rare Plants, Peperomias, Episcias, Hoyas, Ferns & more.

They invite you to visit their beautiful tropical garden nursery, S.W. 66th St. * Miami, Fl. 33173 * (305) 274-9813 Hours - Mon-Fri 9 - 5 * Saturday 8 - 1 )


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