I've been asked to take care of this neglected plant. It looks like a Madagascar Dragon but I'm unsure. I replanted it and now noticed there are some yellow/orange/red spots on some leaves. I don't remember if they were there earlier. Any idea what this means and what kind of plant this is? Thanks!
That is one of the Madagascar Dragon plants. They get these discolorations/spots often from pests, such as spider mites, but can get them from fertilizer residue that dries on the leaves as well. The plants look healthy. You might want to keep the potting soil more evenly moist though and put it on a weekly fertilizing schedule, using 1/4 the recommended application rate (that will usually be 1/4 tsp. per gallon). Remember the phrase: "Weakly-Weekly". The plant does best in bright, indirect light and in warm conditions. They will take lows in the 30's but won't take a heavy frost or lows much below freezing.
Ken
Dracaena marginata
It prefers a soil that drains much better and has better aeration than the soil it's in. We know your soil doesn't drain well because it's comprised of mostly fine particles, which means that after watering there will be a saturated layer of soil near the pot's bottom that limits root function, and in doing so, limits your plant's vitality.
With all due respect, I don't think anyone can give meaningful advice about how you should fertilize without qualifying the advice or at least some sense of what you're using for soil and what your watering habits are. Also, fertilizers are available in an endless variety of concentrations, so 1/4 tsp of 24-8-16 delivers twice the volume of nutrients as 12-4-8 ..... and both fertilizers have the same NPK ratio. Obviously, some consideration needs to be given to what you're actually using.
Let's say that because your soil is so water retentive, you're watering just enough to moisten the soil - so it doesn't stay wet so long. In that case, 1/4 tsp/gallon/wk can very quickly become lethal. As dissolved solids from fertilizer solution and tap water accumulate in the soil, it becomes increasingly difficult for the plant to take up water. The level of salts in the soil solution can become so concentrated that it reverses the flow of water into cells and actually pulls water OUT of cells (plasmolysis), exactly as curing salt pulls moisture from the cells of ham or bacon.
Your plant is particularly sensitive to high fertility levels (EC/TDS) and compounds containing fluorine, like fluoride. Both are most commonly responsible for spoiled foliage, with soggy soil that inhibits root function and water movement to the upper plant not doing the foliage any additional favors.
Ideally, you would have this plant in something like a mix of Seramis (you can buy it in most of Europe), spruce bark, and poultry grit - something coarse enough that you can flush the soil when you water w/o worrying about prolonged soil saturation. With this type of soil and good watering habits, you can fertilize regularly (every time you water if you like) at low doses. A fertilizer with a RATIO of 3:1:2 is best for this plant. RATIO is different than NPK %s. 12-4-8, 24-8-16, and 9-3-6 are all 3:1:2 ratios.
The effects of fluoride are accumulative in this plant, so the older it gets, the more likely it is to show toxicity symptoms, so watering with rain water, snow melt, distilled water, RO treated water will help your plant's remain pristine, as will a better soil that offers better root health. A healthy plant isn't possible unless the root system is healthy.
Finally, this plant prefers a narrow pH range because pH that's too low causes the fluoride issues and if it's at all high, Fe deficiency results.
Al
Al
