I got two tiny grapefruit seedlings for free and I don't know how to care for them. They are in very small pots and all the care they are getting is watering. They are 2" tall. I don't live in the right zone for these, and I don't have any idea how to care for them. How do I grow these indoors under artificial light? Edit: I need an answer fast. Two of three trees are now dead.
In the mid-ninties (probably '94), I planted several grapefruit seeds. Several germinated, and they all got some white fuzzy stuff on them that made them sticky, and all but one of them died (maybe it was scale or something). The one that lived recovered, and I didn't see the white sticky stuff again until about twenty years later (but there wasn't very much of the stuff, it didn't last long, and it didn't harm the tree).
The tree that lived grew fine treating it like the other houseplants. I just watered it, pretty much (and at first, I misted it once in a while, since I heard that was good for citrus trees, since I'm in a semi-arid area). When it got bigger, I gave it fertilizer once in a while (24-8-16). It grew and lived with the same soil and treatment as the other houseplants (it does like more light than a golden pothos, though; it likes to be by a window). It's still alive, today, in fact.
We gave it bigger pots as it got bigger (and like many plants, it seems to get bigger the bigger the pot is). It has been an entirely indoor plant its whole life.
It should be noted that every once in a great while, my grapefruit tree's leaves shrivel up and then it puts on new growth (it's doing it now, in fact). It doesn't happen often (less often than once a year). I think it usually only happens if I forget to water it for too long, or don't give it enough light, or something (but it could be a coincidence and just do it on its own when it wants to). FYI: It's growing new shoots now.
The tree tends to put on more growth when given fertilizer, or when given supplemental lighting (it got a little supplemental light one year when I was starting tomatoes, watermelon and stuff indoors, as my tree was next to the growing environment), but it can be fine not growing for long periods. My tree was very small for a really long time, and it grew very slowly, but gradually came to be able to grow faster as it matured. I imagine if you gave it lots of light early on, it would grow faster.
I don't know the ideal conditions for grapefruit trees generally, but for my tree, that's my experience. My tree could be special, though; it is the only one that survived that infestation. Other than that, it hasn't been bothered notably by other pests (not even spider mites). It's never had any diseases, to my knowledge.
Germinating the seeds is pretty easy. I think I sprouted mine in plain potting soil, since that's what we had (not seed-starting mix). So, they must handle larger amounts of nitrogen better than tomatoes do. Anyway, if you want to keep trying (if your trees didn't live), you might find a tree that lives.
I've never had flowers or fruit on my tree. I'm guessing it might need more light and phosphorus for that.
There are a few common issues with citrus grown indoors.
I have seen them get 5 or 6 feet tall indoors, we are talking a plant that wants to be a tree!
If it gets enough light indoors normally the environment is dry enough to encourage spider mites. Seeing your citrus webbed by mites is not a pleasant sight. Higher humidity discourages mites. Soap and water will control but not eliminate an advanced infestation.
most soil less mixes popular for indoor mixes are ph neutral. If you have alkaline water over time the soil mix becomes alkaline and nutrient deficiencies can show up. The most common is the veins of the leaves are green and the rest of the leaf is yellow. Normally this is a deficiency in iron or manganese. I deal with this by adding garden soil yearly. It may be as alkaline as your water but seems to have more accessible nutrients.
oh, and very sharp thorns
There is lots of info online concerning growing citrus indoors. I know grapefruit trees get pretty big and so may be a challenge to keep indoors after a few years but you're not at a point to worry about this yet.
There are the basics to make sure are in place: keep your trees watered but make sure the pots have good drainage and offer room for the roots to grow. Florida soil is very sandy (I can say after having cared for a citrus tree there for a number of years) and so I emphasize the importance of good drainage. If you're willing to invest in your little tree I'd recommend using 'Cactus, Palm & Citrus Soil.' I have purchased it off the shelf at Home Depot here in Boston so I have to imagine you'll be able to find it in PA. I keep a potted blood-orange.
Make sure to put them outside in the sun whenever the temperatures are above 40(F) degrees to soak in as much natural light as possible. In a nutshell I'd say the important points are lots of light, good drainage & protect from the cold/wind.
I hope this advice is not too late and good luck.