Hello Andersp90,
CoPlantNut had lots of good points and my techniques for keeping my Sweetheart Lychee small are pretty much from reading about bonsai and then adapted for each specific type of tree I want to keep small. Each type of fruit tree has different optimum growing conditions and research should be done well before planting your trees. Of special importance is the pH, salinity(can't remember the term) and preferred moisture level for each type of tree. Some trees like Avocado's really dislike wet feet and most varieties of Avocados dislike high salt levels in their soil. High salt levels can build up over time with repeated use of artificail N-P-K type fertilizers.
In order to keep your tropicals small, I would recommend you plant each of your tropicals in the best type of soil for that particular type of plant BUT keep in mind that you are trying to keep all your plants in pots and many plants do not like wet feet which can lead to root rot and attack by phytopthora(might be same thing). In many instances, you will want to do like CoPlantNut recommends and plant in Al's Gritty Mix or 5-1-1 mix. Al's Gritty mix is pretty heavy however but at least it is fast draining. Many of the fast draining soil mixes are good for your plants long term health but in order to keep them happy when the temperatures are high, you may have to water large potted plants multiple times a day, especially if they are holding fruit. There are some plants like Lychees that I feel do good in regular organic potting soils even though they hold lots of moisture.
Once you have your tropicals in the proper potting soil, its all about pruning branches and the roots in order to keep your trees small. In the beginning, you may actually want fast growth on your trees so that they can get to fruiting size faster and then you would want to slow down its growth once it gets to your ideal size. Once your trees are your ideal size, limit the amount of fertilizer you give them. I like to use organic fertilizers such as Fish/Kelp emulsion which keeps my plants happy and growing but at a slower rate than if you were to fertilize with artificail NPK fertilizers. If you do use NPK fertilizers, you should look for a brand that has slow release Nitrogen and also make sure it has Macro/Micro nutrients.
Potted plants are watered much more frequently than in ground trees so many of the fertilizers that you apply, whether they are Organic or Inorganic gets rinsed through the growing medium very quickily. To combat this, I often feed my potted trees with very diluted feeding of Fish/Kelp emulsion but I feed much more frequently. For example, I might dilute my Fish/Kelp emulsion to 1:4 the manufacturer suggested concentration but then feed it 4X as often.
When you select your trees to be potted, try to look for plants that are naturally branched very low and tip the growth early on(depending on type of tree) in order to force side branching. You do not want to prune in late Fall as this may encourage tender new growth to be killed off by low winter temperatures. In general, for many of my fruit trees, I like to have about 5 or so internodes/petiole scars on the base of a branch before tipping. I would expect that each of the internodes/petiole scars will eventually push new branches. When forming your tree, you can use weights and wires like I did but be VERY CAREFUL that you do not girdle your tree with your training wires. Tree branches are constantly growing wider and your attachment points to your tree should be checked and loosened very often.
Please note that everything I have described above is for growing a healthy tree in a pot but if you follow my advice, your tree will grow large and you will have to control the size by pruning branches and roots. I know you want to keep your trees small but I do not recommend under fertilizing your trees to control size as this may lead to deficiencies in your trees. You mentioned that you want to maximize fruit harvest so you need to continually encourage new growth as many fruiting trees develop fruit on newer wood. If you have a trifurcated tree, you may want to chop off one trifurcation every several years and allow a new branch to take its place. Every 2-5 years, you can take out another main branch and let a new one grow in its place and by doing this, you can keep your trees smaller and you are rejuvenating your trees fruitful wood.
We may be able to give you better advice if you let us know what specific type of fruit tree you are trying to keep small and fruitful. Good luck and please keep us updated on your progress.
Simon
Topic: Keeping my tropicals small? (Read 2041 times)