Looking After Stem Plants

In a Dutch Style aquarium setup, stem plants are the most commonly used species and need constant pruning and replanting to keep the aquascape looking lush and healthy. I have illustrated my most frequently recurring care procedure, which is replanting Myriophyllum pinnatum. This species is such a fast grower that replanting is required every three weeks. Here’s a photo of the left side of my 800L tank with a rather overgrown group of this red millfoil, three weeks after replanting.

You can leave the millfoil floating for several weeks if you want to propagate it because it will develop abundant side-shoots once it has reached the surface. Since this group is large enough, it is time for maintenance:

First, take out the whole bunch by grabbing it near the lower portion of the stems:

Then, lay out each stem on a table in front of the aquarium. (I use a butcher block from a well-known Swedish furniture warehouse). I have sealed the top with a 4mm PVC board. You can also use a plastic bag or similar. Don’t prune your plants on an unsealed wooden surface though because the wood will suck up the moisture and your plants will dry out more quickly.

Now, trim off the lower, rooted portions of the stems and dispose of them. Again, if you need to propagate, you can keep some of the bottom portions for re-planting but be patient. Propagating M. pinnatum this way will be considerably slower than the method described above.

I usually replant in three rows so I trim away the stems at about 20, 18 and 16 cm to obtain cuttings of the right length.

Now, I start replanting at the back, using the longest cuttings, and working my way back to the front row. It takes some practice to get cutting lengths right the first few times but this procedure will soon become routine. If you discover that you left some of the cuttings too long, you can always pinch off the bottom parts between thumb and forefinger while replanting. When you re-plant, use long, finely pointed forceps and stick the cuttings into the substrate for a depth of least 8 cm. This is important because you’ll need to make some adjustments after 24 hours (see below).

When your’re finished replanting, the stems will not look their best. When stem plants reach the surface, their growth will become floating and not erect. Leaves and stems also tend to grow bigger and sometimes coarser. It will take about 24 hours for the plant to adopt an upright habit again. Compare this group of Myriophyllum right after replanting and 24 hours later:

You’ll notice that the stems have straightened out now and their real length can be judged a lot better. Now it is time for the last adjustment. Pull out shorter stems until you achieve a slightly curved top line, a bit like a shoulder. Each row should start low at the sides and become higher towards the middle. Try to avoid straight rows. It is important to stick the stems in all the way when replanting in order to avoid uprooting your fresh cuttings when making this final adjustment. This the result:

Again, a little practice is needed to get this right so don’t give up if your plants don’t play along the first few times.

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Copyright of images: Stephan Mönninghoff