I agree with verticle placement for a few of reasons.
- When placed horizontally, the stem will frequently curve and warp which allows it to lose contact with the soil (I root mine in peat:perlite). This can result in lower strike rates. By placing it vertically, this is prevented and your strike rating should go up.
- I've noticed that the baby flytraps form on the areas of the stalk that are not exposed to light. When placed horizontally, this usually means that they form on the bottom of the stalk and have to grow around it to reach the light. When planted vertically, the buds form beneath the soil line and can then grow straight up which results in a more naturally shaped baby plant.
- Vertical placement allows for tighter grouping of flower stalk cuttings which makes for more effective use of your space
Also, a couple quick notes from my experience ...
I let my flowerstalks grow until they're just about to flower then chop them into 1-2 inch sections and plant those. I'll cut the flower buds so that they have about 1/4" of stalk attached and then stick the stalk in the soil with the flowers on top. They'll frequently continue to grow and even bloom in my rooting chamber. Then I'll chop the remaining stalk into ~1" pieces and stick each one about 1/4" into the soil media. In my experience, letting the stalks grow this long doesn't seem to affect the strike rating and by having multiple chances for success you'll get more plants overall.
High humidity seems to improve strike ratings quite a bit although it's still highly variable. Bear in mind that with high humidity comes a greater chance of fungus and I'm still trying to figure out the best way to address this. One thing I've noticed is that a fungal attack is not necessarily a disaster. I've had cuttings covered in fungus still able to successfully root so don't throw them out if this occurs. As long as there's living tissue on the cutting, there's a chance it'll bud.
I keep the cuttings wetter than I would normally grow flytraps. Almost to the point that the soil is sodden. The cuttings will need to absorb that moisture and don't have a root system to do it so more moisture seems to be beneficial for them.
Finally, the chance to strike seems to vary by cultivar. By far the most vigorous cuttings for me come from my B-52 clones whereas I struggle with King Henry, FTS Maroon Monster, and even DC XL. These differences become quite obvious when working with hundreds of cuttings but I'm still working to understand the trends.
Even with all of this, my strike rating typically hovers between 10-20% of the stalks although when one succeeds then it'll typically generate 4-12 baby plants.
I'll typically pot up the baby plants once they're big enough for my fat fingers to work with ... usually about the size of a dime. This helps prevent crowding and improves their growth.
If you want to go the extra mile, you can look into foliar feeding with dilute maxsea but I usually don't bother. The biggest boost to growth is definitely when they catch prey and I'm investigating growing a springtail colony just for the purpose of feeding baby flytraps.
I'll also skip the first years dormancy in the interest of growing them out faster. It seems to work well and I haven't seen a downside to growing them in this way.
Through these methods I can usually get plants from cutting to "mature" size in about a year. It's a very easy way to turn one plant into many more.
Please note that many of these techniques apply to leaf cuttings as well. You don't have to wait for the flowerstalk to propagate out your plants.
Hope that helps!