Bubble SIPs are a great way to supply both water and oxygen to plants growing in low light indoors
This is a bubble SIP made from a Glad 48 oz Big Bowl. I highly recommend starting with SIPs by growing some plants in clear plastic containers like this. As you can see below, the root system and soil moisture are visible. You can see exactly what is going on.
Once you gain experience you will be able to grow any terrestrial plant in any water tight container of any size equipped with a SIP bubble reservoir or multiple reservoirs. More about that coming in a future post.
Forget about so-called "self-watering"
One of the worst things you can do when using sub-irrigated planters for indoor plants is to think of them as “self-watering”. There is no such thing and it leads to misuse of SIPs indoors.
With all the incessant lecturing about the need for drain holes in plant containers it is probably difficult to believe that sub-irrigation with SIPs is the best way to water plants in containers … but it is! And, it’s not just a subjective opinion, it’s provable and you can prove it to yourself by understanding how they work and testing them.
The primary feature of a SIP is the reservoir. Stop thinking of it as a water reservoir that the plant can drink from when it is “thirsty." Many houseplant hobbyists have a tendency to anthropomorphize when dealing with “houseplants” i.e. to attribute human form or personality to things not human.
Plants do not have a brain like animals and humans…and they are immobile. They are stuck in the planter and cannot escape when the oxygen supply runs out. If you constantly add water to the reservoir “bubble” you will drown the plant. An animal can drink and walk away, a plant obviously cannot do that.
With too much water it will sit there and die from lack of oxygen. Death is inevitable as the root system begins to rot.
This is difficult to comprehend when well known companies advertise their SIPs as “self-watering” and claim that you cannot over water the plants. What they do not say is that this is true only when used to grow plants in full sun (10,000 foot-candles) or near full sun.
Indoor plants, however, are typically struggling to grow with less than 100 foot-candles (less than 1% of full sunlight). Over water them and they soon die under indoor low light conditions. This is what has given the so-called “self-watering” planters a bad reputation in the houseplant gardening community. It isn’t the planter at fault but insufficient education and misleading marketing.
There are in fact many greenhouse growers who like it this way. They do not want you to become proficient in the use of sub-irrigated planters. Their business plans are founded on consumption rather than sustainability. The plan is for the plants to die after a while and for you to blame yourself for their death.
A simple method of SIP water management based on what professional greenhouse growers do.
The best way to measure the moisture level in a SIP is to use a digital scale. An 11 lb capacity scale with tare feature will do for most table top plants. I use a 50 lb capacity scale in the CuGreen lab.
1. Start by filling the bubble SIP with water right to the top. Let it stand for a while to be certain all the soil is moist. A couple of hours is fine. You will not harm the plant.
2. Pour the excess water out by way of the fill tube. Or, use a baster to siphon the water. Or, use a piece of 1/4" clear tubing as a siphon if you know how to do that.
3. Weigh the planter to determine its "wet weight" in ounces (Data Point 1). Write it down in a notebook.
4. Wait until the plant uses all of the water and the soil dries down. This should be close to the "wilt point" The number of days will depend on the plant species and the light level. With a clear planter you can see the color of the soil - light color = dry, dark color = moist.
5. Weigh the planter to determine its "dry weight" in ounces. Write it down in a notebook. This is Data Point 2.
6. The difference between the wet (Data point 1) and dry weight (Data Point 2) equals the weight in ounces of the water consumed (Data Point 3).
7. Add half of the water-consumed amount (Data Point 3) via the SIP fill tube. If the consumed amount is 20 oz., add 10 oz (Data Point 4). As you gain some historical data you can confidently modify Data point 4.
If you are growing in natural light, Data Point 4 will vary depending on the weather and season of the year. If growing under artifical light DP4 will remain constant assuming you keep the light(s) on for the same time each day. Use a timer to do that.
Using this method you will keep the soil moisture optimized and in balance. Your plants will appreciate this very much and show it by staying alive and healthy.