My tomato season is over. This year I planted my tomato plants in 20 gallon grow bags filled with MG potting soil. Plants grew very well and they looked very healthy. But as soon as the weather heated up I had a terrible problem with the soil in the grow bags drying out completely everyday. So I had to water the grow bags every day. By the next afternoon the soil was dry as a bone again.

All of this extreme dryness and then heavy watering every day led to a lot of blossom end rot. What can I do next year to mitigate the problem of potting soil being too dry in grow bags? My husband recommended lining the interior walls of the grow bags with plastic garbage bags and cutting the bottom of the garbage bag out so the water could flow through the grow bag, but there would be no moisture loss out of the sides of th grow bags. But I thought if I did this it would not be good for root formation.


When I pulled up the tomato plants out of the grow bags a few days ago, there were roots formed through the entirety of the bag. The soil was a solid chunk of roots.

The whole point of grow bags is for root pruning so it looks like you did it right. However, besides a lack of calcium, BER is mostly caused by uneven watering so if they were going bone dry daily it sounds like that was your main problem. I just commit to watering / feeding them often and when it gets so hot that it is miserable to go outside (like now), I stop watering completely and call it a season. I'm in process of taking up all my plants. The ones in the root pouches were first to go. I have 4 more EB left.

I wonder if a potting mix that retains moisture would be a good idea to use in grow bags. I know we have been warned against that stuff, but perhaps it has a use after all. I hope someone with experience will weigh-in on this.

Linda

Labradors wrote: ↑Tue Jun 23, 2020 1:22 pm I wonder if a potting mix that retains moisture would be a good idea to use in grow bags. I know we have been warned against that stuff, but perhaps it has a use after all. I hope someone with experience will weigh-in on this.

Can you elaborate on why "we have been warned against that stuff"?

Because It has been known to hold too much moisture and rot roots!

Linda

My experience with grow bags has been with using the RGGS, or rather sub-irrigated, so the whole concept behind that system is that the bags provide root pruning and being automatically watered from below, the plant takes up only the water it wants; a lot on some days and a little on others. The key is the potting mix with enough water wicking material in it to keep the medium moist but not water logged. If you want to try again with the bags but not do sub-irrigated, I would first look at how much peat is in the potting soil you are using. You would want above 70% or more. If it doean't have much, you can try supplementing your next bag with some peat or coco coir, just be aware that each will change the ph a bit, so you would need to amend for that. Or don't the folks that do the earth boxes have a mix recipe they use also? That also might be a good option to try as well. I would hope that you could amend the MG soil with the peat or coco. I would recommend those over the water crystals. the mix I use is called Larry's mix and it is 2-1 ratio of Peat to compost with lime, epsom salt and fertilizer.

I use 10 gallon and 7 gallon air pruning pots, some are on a drip irrigation. My experimental grow this year is a deck garden, all the air pots are in a large rabbit hutch tray.
I am going through a ton of water on the deck plants but will nearly half fill the tray with water to try and get 3 days out of it.
I am going to tie in a 30 gallon tank with a low pressure timer to turn on every 3rd day while I am on vacation. I don't plan on doing this next year as this was a test to see how the plants do on the deck. Since the growth has been great, I will be building Wicking Beds in the fall. Also the soil is a heavy amount of peat, vermiculite, perlite and compost mix, I also put wood in the bottom but it really isn't doing much.









I also have an Air pot for my horseradish that I manually water and it was watered every day, I finally got tired of watering and put the air pot in tray and bottom water. Its hard to see but its in the middle of the two beds up on the hill.





These 3 Air pruning pots (left) are on a drip irrigation.






These are grow bags in a pond veggie filter (top filter).





These are grow bags in a pond veggie filter (lower filter).

My growbags are usually 50% compost and 50% potting mix, it's the compost that help water retention. People don't like compost in containers, but with grow bags it can work with this combination.

You can also put the grow bags in saucers. Peat moss by itself retains water well, but once it become fully dried, it have sort of a hydrophobic quality on the surface and the water runs off making it difficult to thoroughly rehydrate if watering from the top.

I don't know about the sides, but you might try mulching the top of the container with a shredded wood mulch or such. I don't use grow bags, but without mulch, my containers dry out in about two days. With mulch, they only need watering maybe every four to eight days or so (and when they need water, they don't need it suddenly). I honestly don't know how it makes such a huge difference. Maybe the shredded wood catches evaporating water.

Instead of lining the inside of the bags, how about the outside? Fit the grow bag into a trash bag but once it's in & filled with a medium, cut off the bottom of the trash bag or make several large openings for drainage. Maybe try this on one bag to see it it works for you?
I used grow bags a few years ago & also noticed the dryness so I did what others have posted above, did the bottom watering by keeping in a kiddie pool & did the mulch. Too much work for me so now the bags are used to store or carry things in the garden.

I don't see the point of grow bags. My friend in NC raved about them, but I find it difficult enough keeping 3-gallon pots watered enough when it's really hot out, and I just don't see the point in growing in bags that can evaporate water.

Linda

I suspect I'll have the same problem. I had it last year with my 10 gal. bag. This year I'll put a saucer under it and maybe with a wick. I will probably need to get creative.

I purchased 10 gallon grow bags for the first time and am planning growing several tomato varieties in them and also for comparison, in ground and in containers. Regarding the grows bags, I would appreciate any elaboration on using saucers under them or bottom watering. More specifically, how long of a period of time is it acceptable for the grow bags to sit in water before root rot sets in. Is a few hours a day OK?

I did grow bags last year for the first time. It nearly doubled the space I could garden. I found they needed to be really wet before planting then in my climate then it was fairly easy to keep the soil in the root zone moist. I had less problems with them then the larger pots I was trying to use. My small bags 1 to 3 gallons size had over 90 % of my micro dwarfs in them and they were in the front yard with full sun all day and of course not much wind protection. I was thrilled with how well they worked.

Traveler wrote: ↑Sat Jan 23, 2021 5:14 pm I purchased 10 gallon grow bags for the first time and am planning growing several tomato varieties in them and also for comparison, in ground and in containers. Regarding the grows bags, I would appreciate any elaboration on using saucers under them or bottom watering. More specifically, how long of a period of time is it acceptable for the grow bags to sit in water before root rot sets in. Is a few hours a day OK?

Just an FYI the grow bags are rated in NURSERY gallons not true gallons like a bucket. It will take just over a 1.5 cubic feet bag of dirt for each 10 gallon grow bag you have so there is not as huge a difference in the soil amounts between them and a 5 gallon bucket. I found last year the grow bags were not the expensive part of the equation it was the cost of good quality dirt to put into them....

Cant help with the standing water question as mine were either directly on the ground or raised above the ground on wood and I watered them when I did the garden. I have seen videos of them set up in kiddie pools so they could be watered by filling the pool but...

I've experimented a lot including the kiddie pool. When I did the kiddie pool, I used an upside down colander inside the bag so there would be wicking and the mix wouldn't be saturated. I haven't done the kiddie pool in years.

I do use root pouches (fabric bags) and th8s year I even elevated them with bricks around the sides. I previously use to elevate everything and those years were some of the best for tomatoes in every aspect. On any replacement plants I'm doing, I got some inside/out carpet and cutting to fit and putting under the Root Pouches.

I get great production using them except they get so GROSS early in the season. I pressure wash them at the end of the season and this week when it is warmer, I will do so with a porch pressure washer with the plant inside. I've done that a lot.

Earlier in the fall, I bought tan fabric bags thinking they wouldn't get as gross and they were worse.

I get a lot of years using them and although the pressure washing probably shortens their life, I then double the old ones up.

I actually read they say to use your washing machine to clean them. haha

Using Grow bags requires a learning curve for sure. My first year I had BER pretty bad. My 2nd year I over compensated and had mold problems. The last 4 yrs have been trouble free since I started using a moisture meter to check the grow bags every day. Of course I still have to water my 15 gal. grow bags at least once per day (twice in July & August) and I know for many folks this is too labor intensive but for me the rewards have been great with more productivity than I ever got in almost 40 yrs. of growing my tomatoes in ground. I only grow 8 or 9 tomato varieties along with 6 or 7 pepper plants these days and I can keep up with hand watering them. When I can get 60 or 70 tomatoes per plant it makes it all worthwhile, at least for me.

Dan

@Yak54 Can you post a link to the moisture meter you like please. Also curious what reading you like to shoot for?

https://www.google.com/aclk?sa=L&ai=DCh ... Qx6BAgCEAE

OK Sonkir is the brand I use and I've checked them against each other to make sure they are not giving me bad info. If when I get a new one it doesn't give similar readings to my others then I send it back for a replacement. I get them at amazon for 13 or 14 dollars. I have 7 or 8 of them cause it takes at least 10 min to check each grow bag and if you have 9 bags to check that's more than 90 min. so having multiple meters speeds things up. By the way these things are supposed to have 3 functions. Light, PH, & Moisture. I only use the moisture setting and I'm pretty sure the PH function is pretty lame. I try to keep my grow bags reading between the 4 & 6 numbers.

Dan