Hi! I have a Christmas cactus that my girls got as little 1-2 leaf trimmings from a local botany museum. It is growing really well and every branch has little bulbs forming but the leaves are flimsy and limp.

It is currently in a soil blend of cactus and perlite. It was sitting in a south facing window and I thought that might've been too hot so it is now in indirect light.

Any advice as to how to plump up those leaves?

The little "bulbs" that are forming are the flower buds.
These plants for me have been plants that bloom spring and fall as daylength changes. They need a few hours of sun per day to help produce healthy growth and flower production.
They are succulents so the soil mix sounds pretty good. Since they are succulents, they do not produce deeply penetrating root systems. I would water it to a depth of an inch or so, then let it dry out between waterings. You may be watering either too little or not often enough. The leaves start to shrivel over a longer period of low water. But if you increase the frequency a little bit they will perk up rather quickly and within a month or so the plant should look a whole lot better.

So these will eventually open into flowers that's wonderful! So it's technically in its growing period now.

I don't water it often so maybe I will gradually give it a bit more over the next little while. Is there a good time to fertilize it?

Yes. Flowers are very rewarding!!
Most plants that we grow indoors, ferns, African violets, cacti, orchids, whatever do NOT need a lot of fertilizer.
A water soluble food is the easiest to use. Even supermarkets often carry something. Just feed it twice a year, spring and fall. Follow directions!

Wonderful thank you so much!!

Oh, you are very welcome.

Some people will say there are three different cactus in this group and other will say 2. From the pictures you have shown, this variety will prefer to bloom either around Thanksgiving or Easter. The hint is the pointed edges on the stems. Christmas cactus have rounded edges. That does not mean it will not bloom around Christmas partly do to some recent genetic engineering and hybridizing of the different varieties.

Originally these plants were epiphytes which naturally grow on the limbs of larger trees in jungles of Brazil and similar environments.

They will prefer a bit more water, especially during blooms. You will know if you are over or under watering because the blooms will drop off before opening or limbs will break off. Because they are adapted to be on tree limbs high in the tropics, having their roots wet and then drain relatively dry is normal but the humidity is a bit higher than what most true cactus get. So you will need to experiment a bit to see where the watering in your particular home will match what the plants need. They are pretty hardy so minor mistakes probably will not permanently harm them. Once it gets a good growth on it, you can prune it and pot the cutting to experiment with in other parts of your home or give them to friends.

The plants naturally droop once the limbs get longer. I suggest looking at images of other similar cactus on line to see what the growth pattern can look like.

People do put them outside during spring thru fall. You just need to avoid any frost in early spring and late fall and toomuch direct sunlight. Growing in rainforests on tree limbs tend to limit the light they get.

They will acclimate to outside sun but may burn back a bit so gradually exposing them will help. I am in middle NY State so I will put them out on the north side of my house and slowly move them into more sunlight so they gradually get exposed to morning light. I do not keep them in full sun on the south side of my house. The sun gets too intense, especially in summer, and sometimes too dry in August.

The flowering is light sensitive so, if you have bright lights that you turn on during the Fall or Spring, this can disrupt the blooming cycle and they will not form flowers or the flowers will drop off. They need about 14 hr of dark for about 6 weeks to trigger the blooming. If you break this dark period with house lights, they may not bloom.

Excellent advice!

I agree, those are buds on your plant so you will soon see the pretty blooms!

These two have the common names of Holiday Cactus, Thanksgiving Cactus and Christmas Cactus:
Christmas Cactus (Schlumbergera truncata) has pointed leaf segments.
Christmas Cactus (Schlumbergera x buckleyi) has rounded leaf segments.

This one has the common names of Easter Cactus and Holiday Cactus:
Easter Cactus (Hatiora gaertneri) has rounded leaf segments.

I have cared for a few in this group for many years. I've been troubled by this 'limp leaf' thing too, at times, some plants. This is one plant that I cannot fully figure out. But you have good advice and the buds are a great sign

sallyg said:I've been troubled by this 'limp leaf' thing too, at times, some plants. This is one plant that I cannot fully figure out.

I'm glad I'm not alone! I've been stressing over this little cactus for a while simply because I've given it what it needs but can't figure out why it's leaves are so droopy. The plant seems healthy as every end has little bulbs but I can't figure out why it's not plump like other cacti I've seen.

By plump, are you thinking the segments should be more rounded? They're supposed to be flat.

sooby said:By plump, are you thinking the segments should be more rounded? They're supposed to be flat.

I know they're supposed to be flat but mine are paper thin. They don't seem as hearty as others

Are you absolutely sure that you are providing enough sunlight?
I am wondering if inadequate sunlight is keeping them limp? My grandmother gave me 2 before she passed back in the mid 90's. These were by no means beautiful plants but they had a trunk to hold them upright and several stiff main branches or limbs. She cared nothing about new soil or plant food. She was just an old farm girl from north central Connecticut yet her Christmas cacti were gorgeous! She had them in a corner of her den on a little drop leaf table and they got sun from like 9 in the morning until 3 or 4 in the afternoon and when these things bloomed, it was like a pink waterfall!
I did not move them with me when I went to Florida but gave them to a friend. I wonder if they are still alive but grandmas plants were never droopy, in good sun and were kind of neglected. Yet they bloomed like crazy.

Mine sits in a south facing window all day. It gets pretty hot (especially during the summer) and it's actuslly my jade's favourite window as well

I'm just at a loss haha

Again, I'l say, the Thanksgiving cacti can defy all my plant logic. Mine too, certain ones, have papery thin segments, others have thick rubbery segments. One would think they need 'cacti' type soil but these aren't truly cacti, but come from cool forest, right?

All I can think is they have very fine thin roots that can easily die off. One of mine did, on taking it out of its pot there were no roots.

I would not disturb this while in bloom, but may in spring, investigate the roots.

My Christmas cactus looked the same way for a long while. I started with cuttings, and one or two didn't take root for what seemed like forever. Flat, and droopy. Then all of a sudden it perked up and now it's super happy. I think it just needs a little time.