Tuesday, June 24, 2014

Dividing Juncus effusus - Soft Rush for Ponds

This winter had heavy casualties in many gardens. However, we thought this Juncus effusus was going to kick the can. Thankfully, it shows signs of vigor and in fact signs of necessary division.

Taken out of the marginal section of the pond, you can see it has clearly grown right out of the liner pot.
Not to worry, with sharp tools and some elbow grease, it can be divided and replanted.

First, cut the excess root mass that grows through the tiny holes in the pond pot. A tight toothed saw blade worked. Cut off any side shoots and if you can keep those with roots, they can become new plants for another pot.
Once free from the plastic pot, this is the tricky part. Either use the sharp saw and begin slicing the plant in half by cutting the root mass or, take two garden forks. Stab both forks in the middle of the root mass and pull apart; as shown above. It really helps to have two people doing this.
They generally come free with a little force.

If you want more, keep dividing. Remove any browned blades and any baby shoots that have little root mass left.
You must use a pond pot, or a pot with perforated holes dotted throughout for drainage and moisture to get in. Line with landscape fabric or pond fabric. Cut the liner to about 3 inches more than the pot and cut away any excess.
Add grit to the base and clay if you have access. This weighs down the pot and also allows for drainage.

Add a good layer of bagged pond potting compound. It's quite heavy and all the organic matter has nearly broken down. So as to not cloud the pond when submerging.
Place your divisions, giving ample room for further growth. Cutting back the blades will  prevent energy loss because of the root thinning that took place when dividing. Fill in the empty gaps with pond soil. Some pond books recommend inserting fertilizer tablets to help the plants grow. This plant fairs well with the above and as the original plant can attest, it grew out of its pot rather quickly. I really don't want to have to do this again...any time soon! ;)

Add more grit as a topping - preferably different grades. Larger stones are welcome, as they camouflage the pot when it's covered with water, plus the added weight is welcome. If you have fish in your pond, they love sucking up the tiny stones and spitting them out of the pot. Larger ones deter the fish from doing that.

Lay on top a good inch or so of grit. Tamp down. If you are buying grit in a bag, wash before using. This prevents the pond from clouding - especially if you have several pots to submerge.
Soak the pots before submerging. This also loosens any soil that would instead float to the surface. It prevents bubbling and helps to weigh down the pot, so they sink faster.
So, from one pot, 3 were created. They are submerged about 6 inches down. Perfect little edge for birds to hop along and find shelter when getting a drink.


  1. Really helpful, Heidi. Best explanation I have found! I know the post is a little old, but could you comment on what to do for a small bog filter? That is, should the plants be put in a pot? I have a new bog filter but it is not big and the juncus I got is kind of big so I was thinking I would try to divide it and then plant it. Not sure if it will overrun my small bog filter if I re-plant it out of the pot, not sure if it will work to clean the bog if I keep it in the pot. Bog is 15" × 46", next to my new fish pond 46 x 60.

    1. Depends what sort of bog filter. Does it have a permeable base like clay or a rubber liner? I'd say for both it's ok, but in a clay situation, the Juncus may take over. You don't want them to suppress other plants to help filter water. If you plant Juncus in pond pot liners, at least their roots will not take over and they'll be easier to remove if you need to divide and keep them controllable.


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