Water Tub Gardens. What should I consider?

[Marck]

Hello All:

A few months ago, I set up my first tub garden. I hope to eventually have three or four of them. My interest is in growing ornamental aquatic plants, not fish. I've been reading a lot about ponds and water gardens but their is so much to consider, and much of it doesn't necessarily apply to my situation.

Let me explain my set-up, and maybe some of you experienced experts can advise me.

• My tub garden is oblong, forty gallons. It gets more than half a day of sun.
• It contains a selection of emergent aquatic plants in containers set at varying depths.
• I used fertilizer tablets at time of planting but have not fertilized since.
• I'm controlling mosquitoes with a weekly does of BTI flakes. No problem there.
• The water is a mixture of collected rain water and chloramine-treated tap water. I'm not that concerned because I have no fish, but perhaps residual chloramine can also effect plants? Please advise. There is one accidental tadpole in the tub that seems to be thriving, at least so far.
• I have added no chemicals to treat chloramine, ammonia,or pH, etc. I am also not pumping or filtering the water in any way. I'd rather not if I don't have to, but what do you think?
• Beside the emergent plants, I've also put a large amount of Azolla and duckweed in the tub. I like the way it looks and I also like that it will shade out algae. Azolla also fixes nitrogen, which may be a plus or minus.

Basically, I have four main concerns:
1. Residual chloramine from tap water. Will it have a negative effect on plant health?
2. What should proper oxygen and nutrient levels be, and how do I achieve them. I'm concerned about both too much (toxicity), and too little (inadequate growth).
3. Will Azolla and duckweed be fine in a fishless tub garden. or will it cause any unforseen problems?
4. What else should I be thinking about and asking about that I might not have even considered?

By the way, I also grow a lot of wetland plants in pots that I place in saucers of water. They basically act like small container bogs. Their maintenance is much more like terrestrial gardening, and very different from true aquatic gardening.

Thank you for reading and for any advice your might provide.

 

[JRS]

Welcome to the forum. With no fish, for which oxygen and ammonia are critical factors, and emergent plants, I believe most of your concerns are not an issue.

1. https://www.gardenmyths.com/chlorine-chloramine-plants/
2. Unless you have someway to measure, I would judge by your plant growth/condition and develop a dosing schedule. Don't forget the possibility of needing trace elements if basic fertilizer is insufficient.

The Azolla and duck weed will use nutrients is the only issue I can think of. With no fish filtration/aeration should not be necessary.

 

[brokensword]

I might add, without water movement, the mosquitoes will like your water tub gardens. They don't like moving water for laying eggs.

 

[Marck]

Thank you so much for the replies.

I guess I'll continue as I have been. I suppose if I have any water quality problems, I can always do a partial water change or try reducing the coverage of Azolla and Lemna.

I'm still concerned about obtaining good plant growth, but I suspect that any slow growth I'm seeing is due more to lower Winter-Spring temperatures than nutrient availability. Actually some plants I have put in are already growing quite quickly, such as clover fern (Marsilea mutica), but others such as alligator flag (Thalia geniculata) are hardly growing at all. Of course it is early in the season, I'll have to post an update in mid-summer.

BTI is working great on controlling mosquitoes. The tub is also small enough that I can spoon out most Culex egg clusters that I find, but BTI is my main line of defense.

 

[JRS]

I was wondering what you used for planting medium in your pots?

 

[j.w]

I had Azolla and Duckweed in one of my tubs and in the long run for some reason the Duckweed took over the Azolla and Azolla is no more. One thing about either one of those they can take over the whole surface of a pond w/o fish!

 

[Marck]

My planting medium: I planted my plants up in from one-gallon to two-gallon containers, using a heavy, sandy mix actually designed for succulents, I topped that off with an inch of gravel. The mix was weighty enough to prevent any floating soil but it had very little nutrients in it. I bought most of my plants in one-gallons from a local nursery. They were leftovers from the precious year so I was able to get them in a dormant state in late winter.They were growing in a heavy clay-like medium.

That is interesting about the duckweed taking over. I'm wondering if decayed Azolla and duckweed will take the place of fish droppings for self-fertilizing the pond, but it might also create an unhealthy anaerobic situation. I'll continue to monitor the situation.

I'll discover over the course of the coming year what plants will grow best in my conditions. I want to grow a wide variety, but I know they will all compete for light, space, and other resources. So far they are all alive and have shown at least a little growth, very little in the case of the Thalia. I'm in inland California, so the summer will be long and hot, but it is usually a dry heat. Without much humidity, the nighttime temperatures can fall into the 50s or 60s, even when daytime highs are in the 90s or above. It will be interesting to see how plants from more humid or tropical climates will tolerate cool nights.

 

[Tula]

I have a small deck pond for plants and I use a small pump ( fountain pump ) to gently move the water.....doesn't bother the plants and keeps mosquitoes away naturally.

 

[JamieB]

You’ll want additional nutrients for the plants. Look on line for a good one, possibly designed for planted tanks, with trace minerals. That should boost your growth.

 

[Marck]

Yes, developing the right fertilizing regime will be one of my main challenges. Tablets seem to be the usual choice, but I am open to other options. What does anyone think about using either those plastic Laguna fertilizer spikes or Jobes spikes? I know that Jobes spikes aren't made for ponds, but I have read that some have used them with good results. The shape of a spike is much easier to insert in a submerged pot than a tablet...

If I can keep the surface shaded with Azolla & Lemna, so that algae can't take over, I might be able to get away with a small amount of liquid fertilizer in the water.

 

[Lisak1]

I've used the Jobes spikes in my pond plants - you are correct that the spikes are so much easier to jam into the pot, especially once they get densely rooted. I don't know why they make the aquatic fertilizer in tablets - someone's in charge of product design who's not really using those things. I bought one supersized package of Jobes spikes one time that came with this plastic pre-spike (for lack of a better word). You stuck the plastic thing into the soil first to make a hole for the fertilizer spike - genius! Even the spikes can get crumbly and kind of fragile. But of course I misplaced the most useful thing ever!

One caveat - I do find my waterlilies respond better to aquatic fertilizer or even Osmocote. The Jobes spikes are just OK - I don't get the vibrant growth and blooming that I do with other fertilizers. However, some years I'm ok with that... less growth means less grooming!

 

[Marck]

I thought I'd post a few shots of my water garden tub and discuss my progress.
The first photo was taken in mid-March before the Azolla and Lemna went in. The second one was taken at the beginning of April, immediately after I added the Azolla and Lemna, and the last two were taken 19 and 25 April, respectively.

The tub is beginning to get crowded. I will probably prune back the clover fern soon. The Thalia is still growing very slowly, but the other plants are showing respectable growth.

Mosquitoes do not like ponds with a solid layer Azolla and/or Lemna. I haven't found any Culex egg clusters since the Azolla and Lemna have filled in, but I still put in B.t.i. once a week just to be sure. The name 'mosquito fern is misleading. Azolla is called 'mosquito fern' because it discourages mosquitoes.

This weekend I hope to start a second tub, and plant it with my first Nymphaea!

If anyone is curious about which plants I'm growing in the tub, here is the list:

• duck weed (Lemna turionifera, probably other spp. too), floating
• mosquito-fern (Azolla filiculoides), floating
• floating hearts (Nymphoides peltata), planted in a submerged container
• water poppy (Hydrocleys nymphoides), planted in a submerged container
• pickerel weed (Pontederia cordata), planted in a submerged container
• red-stemmed alligator flag (Thalia geniculata), planted in a submerged container
• clover fern (Marsilea mutica), planted in a submerged container
• bog-bean (Menyanthes trifoliata), planted in a submerged container
• parrot-feather (Myriophyllum aquaticum), currently floating, but I may plant it later
• primrose-willow (Ludwigia peploides ssp. peploides), currently floating, but I may plant it later

 

[Marck]

I had Azolla and Duckweed in one of my tubs and in the long run for some reason the Duckweed took over the Azolla and Azolla is no more. One thing about either one of those they can take over the whole surface of a pond w/o fish!

I'm not sure yet, but I may be experiencing the opposite situation. My Azolla is taking over an ever larger percentage of the water surface, at the expense of Lemna (duckweed).

 

[j.w]

@Marck I have no clue why one takes over and the other disappears. They are supposed to be able to grow together which mine did for a long time. Then I moved them out of the small pond to do some work to it and put them both back in. That's when the Azolla started to disappear. Maybe I damaged the Azolla by moving it? The Duckweed just grew and grew. I think I read that Azolla does not like moving water at all. Not sure how much moving water the Duckweed can handle but I don't think it likes much either.

 

[Tula]

I love the floating plant that looks like shamrocks, is that the floating hearts? I see another floating plant I originally thought was a lilly, but it's heart shaped.