I currently have a dozen rare Black Twig Lime seedlings growing. Two weeks ago my first seedlings reached its 18th inch of growth, therefore I clipped the top. Just today, I counted the new side branching that this process produced. The tree now has 10 new side branches. Many of us have seen pictures proudly posted on this forum by members showing a seedling tree which had never been topped. The result shows a very tall weak, thin sapling looking specimen requiring a stick to hold it vertical. By clipping the top of my tree, it probably lost only two weeks to a month's growth, but has gained a well balanced pleasant form that will result in strong foundation branching. I completely agree with Laaz. - Millet (149 days to go)..

We're all discussing seedlings that have reached roughly 20" (half a meter) in size, but I doubt Svens seedlings are anything near that size already but have just germinated instead. Considering the climate Sven (and I) live in, it may take some time (a couple of years maybe) until that size is reached. I think it is just too early to start thinking about clipping the top.

In my personal experience with seedlings (seville, grapefruit, poncirus, valencia), they usually start branching out by themselves in the second year. The plants are only 4 or 5 inches in size at that age.
Only a lemon seedling that I have growing did not want to start branching out but grows up as a long, thin, very flexible twig. I did top it off once. The result: two new shoots that continued growing like the original. It is still a long, thin, flexible plant. Ready to throw out...

Why don't you try budding it? If nothing, it's a good practice. Budding anything thicker than that, later on, would be a piece of cake.

I believe the growth of a young seedling depends much more on the grower than the climate. A seedling tree should reach 2 feet or more by the end of its first year in most any climate, if given proper heat and light (either natural if possible or artificial if not.) . - Millet

I agree to Marc.

All my seedlings branch themselves in second or third year.

What ever we do, the citrus tree will never grow like in the citrus areas.
We can be lucky if it grows 30 % as it does there.

Why on earth would anybody intentionally wait for three years, over 1,000 days, for a citrus tree to branch out, when it is so easily and beneficially done in the tree's first year ????? - Millet

Of course it plays a significant role, beside environmental conditions.
You can start feeding them as early as 4 weeks old. Although I wouldn't recommend you using anything stronger than a half strength solution.

Take care,
Igor

Sven,

I believe you can mix a slow release fert in the medium you place your germinated citrus seeds!

Good luck!

Osmocote makes a special slow release fertilizer 18-6-12 that can be incorporated into the germinating medium at the time of planting the seed. Incorporating it at the rate of 80 grams per cubic foot of seedling mix significantly increases plant height, number of bud breaks, stem caliper, top weight, and root weight. - Millet (145 days to go-)