Stem plants are usually seen in the background of the tank. If they’re left alone, most will grow to the top of the tank and across the surface or even out of the water! Because of this, if you’re going to keep stem plants you’re going to need to trim them at some point. But each species has unique lighting requirements, nutrient preferences, growth rates, and reactions to trimming which you’ll learn as you keep that particular plant for longer. I hope that this article can help you learn when to use what trimming techniques to keep your stem plants looking their best.
To start, you really only have two choices of where to trim: the top, or the bottom. You trim from the top of a stem to make minor adjustments in the shape of the group it’s a part of. You trim from the bottom when you need to make major adjustments to many stems at once, like when a group starts to overshadow shorter plants. I find that the perfect time to trim is while doing a water change, and when I’m only top trimming that’s enough time to keep everything looking good for the week. Every month or so the plants get too tall and I have to do a bottom trim which takes a little while longer. This routine creates a cycle that starts just after the plants have been bottom cut to their minimum height. As they grow upward, they’re trimmed from the top to maintain the bunch’s shape, and when they get to their maximum height, they’re pulled out, trimmed from the bottom, and the cycle repeats.
Trimming from the Top
When cut from the top, a stem plant will sprout new stems from the end of it, usually just above the highest node left after the cut. To maintain the slope of a bush, use your scissors to cut an angled plane through the top of the bush. There’s nothing fancy about it, just bluntly cut in a straight line through the group, like sculpting ice. Be sure to to cut the whole group at a time so the individuals grow back together evenly, but try not not to cut too low and into the less healthy part of the stems, which will slow their recovery time. Now your bush doesn’t look as good as it used to, but in a couple weeks it will be twice as dense and shaped more like your vision.
If your bush is growing fine overall, but there are a few strays, trim them slightly above their neighbors. The injury will slow their grow and allow their neighbors to catch up, keeping the stray more in line.
Replanting the tops that you trim off is a good way to quickly increase its quantity. Replant them towards the front where you can see them and be sure they’re getting enough light.
Replanting
The physical act of replanting the groups or individuals also requires different techniques for different plants and substrates. A must-have tool for a stem plant grower is the aquarium tweezers. Tweezers allow you to grab groups of stems and wedge them securely deep into the gravel without uprooting any other plants nearby. Your other option is your fingers, which will have to be learned with experience. Some people suggest burrowing a hole with your finger and slipping the plant in, others say try to push, scoop and swoop technique. You’ll figure out something that works for you, but none will be as effective at planting groups densely as tweezers, your fingers are just too big.
Trimming the tops of stem plants is where you get the chance can express the most finesse and skill. You want to trim from the top to tweak the shape of a growing bush.
Not all plants respond well to this type of trimming though, particularly the slower growing types, so be sure to know before doing a bulk top trim on a new plant. Most will eventually come back and you’ll have two new branches in the end, but the plant will look awkward for a long while until the new branches grow in.
Here is a list of plants that don’t respond well to top trimming:
• Hygrophilia Corymbosa
• Ludwigia Repens
• Ludwigia Glandulosa
• Ammania Gracilis
• Polygynum ‘Sao Paulo’
As I said before, trimming from the top of stem plants is where an aquascaper can really express themselves, and it’s impossible to give a definitive guide on how to do it. When trimming from the top, you’ll do it either in bulk or by individual.
Trimming from the Bottom
You trim the bottom of a stem to change its height to something more desirable for your layout. To trim stem plants from the bottom, take a group in your hand and hold them such that the tops are relatively in line. Then cut the entire group at the same location, at the desired distance from the group’s top. You can use scissors to make the cut, but I haven’t seen any obvious negative effects from ripping groups of smaller stems in my hands.
Finally, replant the group in the gravel using tweezers or your fingers. See Replanting Stem Techniques for more details.
Maintaining shape
Bulk top trims are used to direct the long term shape of a bush. By cutting many stems at once, and at specific angles, the aquascaper is laying the groundwork for the future look of the bush. To do a bulk top trim, leave the plants in their normal location. Be sure not to disturb how they are normally positioned in the tank as that can throw off the end result, and cut several stems at once, over and over until you have the new shape you like. You don’t have to be very precise at this; as the plants grow they’ll fill in gaps and slight variances.
To create a bush that rises from front to back, cut the front groups of stems at a low level, the middle third at a slightly higher level, and the rest slightly higher. It’s important to cut all the stems at one time, or the uncut stems will quickly outgrow the recovering stems and break up the consistency of the bush.
Trimming individual stems from the top is used to reign in strays that are breaking the bush’s shape or shading other plants. Be sure to cut the stem far enough above the plants around it so the new branches will have access to light while everything uncut is still growing a full speed. If that’s not possible, you can still cut it from the bottom and replant, or discard as necessary.
Starting over
Eventually your stem plants will reach the surface of the water and it’s time to do a complete bottom trim and start over. There’s no way to avoid it with large bunches of fast growing stem plants and is essential for maintaining a tank with stems in it over the long run.
When doing a bulk bottom trim, pull them out of the tank in large groups and sort them by similar height: short, medium, and tall; then bottom trim them to the desired height. Sorting by height will allow you to strategically cut and replant groups of varying height and jumpstart the progression of a terraced look. Next replant your cut groups into the substrate in “small groups.” The size of a “small group” here varies from one or two for very wide plants, like Ammania Gracilis and Polygynum Sao Paulo, to a dozen like Rotala Magenta and Rotala Sp ‘Green’. In the table below are my recommendations for the group size when replanting. Notice that most of the single group plants are also in the list of plants that don’t respond well to top trimming above.
Single – Ammania Gracilis, Polygynum Sao Paulo
Small (3-6) – Ludwigia Glandulosa, Ludwigia Repens
Large (5-10+) – Rotala Macranda, Blyxa Japonica, Rotala Sp ‘Green’, Rotala Magenta, Ludwigia Arcuata
