making stem plants stay put

I would use tweezers like coach_z described. Another way would be to unbunch them, strip/remove dead leaves & stems, then rebunch 3-4 of the stems with the weight. Don't stick it in the substrate, but let it just sit on top of the gravel. Within a week, the plant will begin to grow some roots to attach itself. Once there's enough roots for anchorage, you can remove the weights and replant them individually. Rotalas and Ludwigia will send out roots when they're above soil. Of course this only works if you don't have large fish that will move unattached plants around.
 
yeah, I bought my first bunch of ludwigia last week. I dropped it in the tank and was waiting for my chance to plant it. I was going to just bury the bunch, weight and all, but came out one morning to find the whole batch missing. I eventually dug out most of the ludwigia stems from the tangle of wisteria at the top of the tank. I have no idea where the largish weight went. I'm still not sure how he did that....

I planted about five or six ludwigia stems, along with a few rotala and a few moneywort and what could either be a moneywort or an odd-looking wisteria. I was pleased to see them still firmly planted when I fed the fish this morning. I'm going to try and keep all sinking food away from that spot for a while.
 
I recommend Kuhlifan's method. I use ADA's "Moss Cotton", which is designed to gradually deteriorate. Have used tweezers to replant wisteria, but often find that the tip pressure needed to get the stem down deep sometimes crushes and kills it, leaving me once again with a floating plant.
 
I've found that trimming the bottom leaves from the cutting and then laying 2-3 inches of the stem horizontally in the sand helps to avoid this. It has the added benefit of putting 2-3 nodes into contact with the sand. the more places for roots to form the faster the cutting takes.
 
Can you make a little fence out of plastic mesh to keep the pleco out while the plants root? You can get some sturdy mesh at a fabric store and use it to corner off a section of the tank with the plants. They should root in a week or two, then you could remove the mesh.
 
i've found that planting each stem individually will provide for the best growth. one stem planted by it self next to a pair or three stems planted together a few inches away always does better in my tank. pruning makes one stem bunch out far better than several stems planted in the same amount of space. a good root structure for each stem seems to be key. i have really been trying to give each stem/plant it's own space to grow and it has really made a difference in my tank.
 
I don't think a cement/steel/force field barrier could keep the pleco out. He sometimes just freaks and shoots around the tank like an out of control battle tank.

Is it bad to maybe put a few leaves under the substrate as a temporary anchor? I realize they will eventually rot, but once that happens the roots should be doing their thing. I have used the method of letting a few inches of stem go horizontally. This can be good from the standpoint of layering rocks over it. To be honest, the plants that have done the best for me in this tank are the ones I put in originally, before there was much water. It's so much easier to get them placed and planted if you don't have to deal with more than an inch or two of water.

A few of the stems I planted two days ago came loose. I brought them in and planted them in my five gallon at work this morning. The neons are much less aggressive/destructive than the stupid pleco.
 
When ever I plant new plants I scoop up a small handful of substrate and pour it over the top of the plant. This creates a little mound around the bottom as well as some substrate will fall on the leaves. This helps hold them down till roots grow. After a few weeks i just knock off what is left on the leaves with my long hanled algae scrapper.
 
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