Gnat attack and other indoor gardening questions

[natale]

Hello all!

I got a lot of great info from my last post and decided to post again about a more relatable topic. I am growing herbs, greens, and some vegetables inside my apartment. I don't have a ton of natural light to work with, as all my windows are north-facing. I am currently growing a variety of salad greens (arugula, kale, spinach, romaine, purslane) herbs (sage, lavender, rosemary, chives, basil, coriander, anise, parsley, peppermint, chamomile, borage, lemon bergamot, echinacea, yarrow, lemon balm, thyme, oregano, calendula, lemongrass, hyssop, fennel, marigolds, peppermint, nasturtium) , and a few vegetables, (tomatoes, several types of peppers, ginger, turmeric, garlic, onion, carrots, peas, beans).

Whether inside or outside, I'm growing everything in large pots or planters with companion plants. All are started from seed aside from the lemongrass and lavender, and I'm growing the onions, garlic, turmeric, and ginger from the scraps or rhizomes. As you can probably guess, I'm having a difficult time with some of the herbs in large planters because the soil is not drying out entirely through the pot, and I'm getting flies and biting gnats. The pots are all about half full of pebbles or styrofoam to help with drainage, but I feel like I'm overwatering, however I also feel like the seedlings need a lot of water to start. I also use several grow lights, to give the plants the light they are missing out on, given the lack of sun from the apartment window.

Does anyone have any advice on watering frequency for seedlings, in general? I know it varies by plant, for example, I'm aware that sage prefers semi-dry soil, while ginger prefers fairly wet soil. I just feel like I haven't found the right balance for these seedlings and they either appear to be struggling, due to lack of moisture, or they're looking healthy, but I have gnats all over the place. Am I shallow watering? Overwatering in general? Will the bamboo stalks I've placed in some pots do anything to help soak up the moisture in the deeper part of the pot where the roots of the other plants are not yet reaching?

Any advice would be greatly appreciated! I've attached some messy photos that I've just taken tonight, after thoroughly watering all of my plants, and spraying them with a homemade insecticide (peppermint soap, peppermint oil, white vinegar, and a tiny bit of hydrogen peroxide). I also realize my homemade insecticide may be harmful to the plant as well, especially with the hydrogen peroxide.

My best and healthiest plants are the ones I barely touch...but they're giant palms and such, not delicate seedlings.

Thanks for reading! Any advice is much appreciated!!

 

[alp]

For gnats and bugs: you can incorporate some horticultural sand on top as they don't like to lay eggs on that kind of medium.

You can crease some tin foil to increase the light amount or invest in LED grow lights.

 

[natale]

For gnats and bugs: you can incorporate some horticultural sand on top as they don't like to lay eggs on that kind of medium.

You can crease some tin foil to increase the light amount or invest in LED grow lights.

Great advice and video!! Thanks, alp! I have been using some LED lights and had wondered about creating a reflective surface somehow. The tin foil is a good idea. Would you suggest laying the foil under the pots, or how would you suggest arranging the foil? I guess I'm not sure what you mean by creasing the foil. I am going to pick up some sand today to see if that helps with the surface moisture/texture.


Thanks for your help!

 

[alp]

I have never used this method. @Logan is the expert in this. When you crease the foil, it actually increases the rate of reflection and hence creates more light. I think you put them as the background of your shelf.

 

[natale]

For gnats and bugs: you can incorporate some horticultural sand on top as they don't like to lay eggs on that kind of medium.


Kind of strange, but I put a heavy layer of sand on top of all potted plants and the flies are EVERYWHERE. I figured this is just because now they aren't burrowing in the soil, so I laid out several fly traps horizontally. I've caught several by now, but they are still everywhere. The soil has dried out quite a bit, it's well drained, there are no other sources in my home for fungus gnats to feed but the gnats/flies are all over. If I go up to a potted plant and shake the pot a little or blow on the surface of the soil, I can see flies crawling around. Any ideas? At this point, they're not just harming the plants, but bugging the hell out of me too.

 

[alp]

Yes, use the sticky tape as it's so sticky that it does do the work, but your fingers will be stuck with the glue and don't ever get it near your window. Or put a cup of cider vinegar to see if it helps. I did that in my propagator. What is your temperature at the moment? Maybe seasons for breeding?! They are probably embedded in your compost. I would boil or sterilise it before use. The air circulation might have something to do with it as well.

 

[MaryMary]

Things to try for gnats...

If you try the potato slices, PLEASE upload photos!!

https://www.smallfootprintfamily.com/how-to-control-fungus-gnats-organically

 

[Bootsy]

That was a good video but it left out something that could help. It told you that the eggs/larvae like the damp soil on top of the pot and that you could use sand to assist keeping it dry. Also letting the soil dry out between watering.

What they missed was that it's best to water the plants only from the bottom. If your plant stands in a plant saucer you only need to add the water to the saucer. This is absorbed by the soil (if you have holes in the bottom of the pot) and you never need to wet the top of the soil. Obviously, if you over water the plant from the bottom then the soil will absorb the water right to the top.

I also remove the top half inch of soil every month and replace it with fresh. This is easily done if you haven't overwatered the plants. the soil on top is dry so you tilt the pot, run your finger around the top part of the soil and it will rub off onto the paper you have placed beneath it. Then add a little more soil.

The vinegar solution is a good one as well but you may wish to restrict the smell of it by putting it in a jar with a lid on and make some small holes in the lid.

 

[natale]

Yes, use the sticky tape as it's so sticky that it does do the work, but your fingers will be stuck with the glue and don't ever get it near your window. Or put a cup of cider vinegar to see if it helps. I did that in my propagator. What is your temperature at the moment? Maybe seasons for breeding?! They are probably embedded in your compost. I would boil or sterilise it before use. The air circulation might have something to do with it as well.

Hey Alp,

glue traps and vinegar are working to some extent. I made the mistake of getting some glue paper stuck to a window last spring. Pretty disgusting. The temperature is 12-25 degrees celsius. It cools down a lot at night but very warm/hot during the day. The air is very dry. I have a small bag of compost that I introduced only recently.

 

[natale]

That was a good video but it left out something that could help. It told you that the eggs/larvae like the damp soil on top of the pot and that you could use sand to assist keeping it dry. Also letting the soil dry out between watering.

What they missed was that it's best to water the plants only from the bottom. If your plant stands in a plant saucer you only need to add the water to the saucer. This is absorbed by the soil (if you have holes in the bottom of the pot) and you never need to wet the top of the soil. Obviously, if you over water the plant from the bottom then the soil will absorb the water right to the top.

I also remove the top half inch of soil every month and replace it with fresh. This is easily done if you haven't overwatered the plants. the soil on top is dry so you tilt the pot, run your finger around the top part of the soil and it will rub off onto the paper you have placed beneath it. Then add a little more soil.

The vinegar solution is a good one as well but you may wish to restrict the smell of it by putting it in a jar with a lid on and make some small holes in the lid.

Hey Bootsy,

Thanks for all of the info. Most of my plants have saucers, but if the soil is rotten, am I feeding the plants dirty water? The plants I have that all do the best are old (aka potted when I knew nothing about any of this stuff) and all I do is put them in the shower once every 8 weeks or so until the water runs clear from them. If they are dry, I am able to water these from the bottom, here and there. Basically flush the soil.

I know I'm shallow watering these seedlings, but the water does drain through, but not after the addition of sand on top. Some pots are 2' tall and the bottom half is mixed heavily with styrofoam packing peanuts and rocks.

I am incredibly into the idea of only watering from the bottom. It makes so much sense, and saves so much water. I'm just not sure the roots are long enough to reach, especially considering all the pieces I incorporated in the bottom of the pot for drainage. I think I would have to dry the plant out completely and then repot to use the bottom watering method.

I've attached more photos. Its quite a bit more of a mess. As you can see, The plants are doing just ok, but definitely doing worse after I sprayed the leaves (which had insects stuck to them). The glue traps have gotten several fungus gnats, I used blue and white sand (I read that gnats are attracted to yellow but repelled by duller colors. Who knows? I'm just willing to try anything.)

Thanks again. I know my messages are lengthy.

 

[natale]

Things to try for gnats...

If you try the potato slices, PLEASE upload photos!!

https://www.smallfootprintfamily.com/how-to-control-fungus-gnats-organically

Mary,

This is interesting for sure! Thanks! So the potato slices are like glue traps but attract the larvae, not the adults? Sounds really gross, but I'm willing to give it a try. Again, at this point, I'm game to try anything, although the more I think about it, the more I think I just need to repot and cut my losses which would include seedlings. I think I've tried all of the other methods listed on the list. Seriously! I've never had an infestation like this or even plant issue that's been such a pain to fix before!

 

[Bootsy]

With your explanation of how you have filled the bottom of the pots I don't think you would be able to water from the bottom.

I don't understand the bit about putting them in the shower until the water runs clear. Why are you doing it. It seems to me that you will be washing out all the nutrients in the soil.

If you're just growing herbs then those pots are much too deep and unnecessary. It's not worth growing herbs for indoors as perennials but do it just for annuals (too many problems can occur). As annuals you are planting seeds each year and you only need shallow pots as their roots don't go down very far.

We sell plants for charity and we sell herb and succulent pots that are all ready for people to just look after. In this shot the front row are herb pots. You don't really need anything much deeper than that.

It's better to grow them in succession if you want nice young fresh herbs. So a few of these type of pots with seeds sown a few weeks apart should work well. A similar thing can be used for salad plants.

Using the 'cut and come again' method you can grow a lot of salad leaves and herbs. It's easier for me to give you links than to explain it. You can also Google 'cut and come again' for more info.

https://www.rhs.org.uk/advice/profile?PID=618

 

[natale]

Hi Bootsy,

Thank you for the info. The shower method was to flush out fungus on some older plants in really large pots.

For the most part, I'm growing herbs in pots with a maximum depth of 8". The larger herb pots are for things such as rosemary and lavender, which I was hoping would grow to be quite large. The largest pots are for tomatoes, beans, peas, and carrots. I did sprinkle in some herbs in the tomato pot, to try to utilize companion planting. I'm using the cut and come again method for the salad greens in the window sill planter which is about 6" in depth, or trying to, but those seemed to shoot right up and then basically stop growing. I don't think the greens have grown more than a half inch in the past month. They've just stopped growing, from what I can tell.

I purchased some new planters. They're basically long, rectangular-shaped containers with a shallow depth, like the planter for the salad greens. I think I'm just going to start over with the herbs, and plant them in these containers.

As for the large containers containing vegetable seeds, my idea was to use something with a greater depth, to bypass transplanting, since I don't have a lot of space.

I think I'm just trying to grow too many things indoors. The gnats are still at large...I actually inhaled one today, because they're just everywhere. There must be something I'm overlooking. Perhaps the soil which I store underneath the table which the plants are on is infested. I know they aren't getting enough light, even though I'm using grow lights and foil. It seems the plants are drying up and dying now, as I didn't water them for a few days and the soil is dry, but there are still fungus gnats crawling all around in the soil/sand. I've also noticed some white mold in areas of the pots, like the corners of the square shaped planters, where its possible the light just never reaches. Again, these are all at a south-facing window, and I just don't think the light is getting to them at the right angle.

The gnats have become such a problem, that I feel like the best thing to do is just ditch what I've started and start the entire process over, making sure to use smaller pots for the herbs and greens and possibly not bother with the vegetables since they will eventually need large pots, but I don't have the space to use starter pods and then transplant. I'm sort of sad to give up on what's started, as some plants seem like they could make it, but I also feel like I'm not being very successful at saving these seedlings. Perhaps if I go through the pots carefully, I may be able to salvage some seedlings.

It's been fairly frustrating, seeing as how the soil dries out so quickly, which appears to damage the plants, yet still grows mold and hosts hundreds of fungus gnats. I can't seem to find the balance. Hopefully a fresh start for at least some of the plants will help.

Luckily, the very limited space I have outside seems to be treating the plants well. Most of the seeds won't grow taller than some kind of ground cover, but some seeds appear to be growing well, with very little effort on my part.

Thanks for all your advice!!

With your explanation of how you have filled the bottom of the pots I don't think you would be able to water from the bottom.

I don't understand the bit about putting them in the shower until the water runs clear. Why are you doing it. It seems to me that you will be washing out all the nutrients in the soil.

If you're just growing herbs then those pots are much too deep and unnecessary. It's not worth growing herbs for indoors as perennials but do it just for annuals (too many problems can occur). As annuals you are planting seeds each year and you only need shallow pots as their roots don't go down very far.

We sell plants for charity and we sell herb and succulent pots that are all ready for people to just look after. In this shot the front row are herb pots. You don't really need anything much deeper than that.
View attachment 36078

It's better to grow them in succession if you want nice young fresh herbs. So a few of these type of pots with seeds sown a few weeks apart should work well. A similar thing can be used for salad plants.

Using the 'cut and come again' method you can grow a lot of salad leaves and herbs. It's easier for me to give you links than to explain it. You can also Google 'cut and come again' for more info.

https://www.rhs.org.uk/advice/profile?PID=618

 

[MaryMary]

Perhaps the soil which I store underneath the table which the plants are on is infested.

You could try to sterilize the soil.

Pasteurizing Medium
Potting media mixed by home gardeners should be pasteurized to kill weed seeds, soil-borne insects, and pathogens. Pasteurization destroys most organisms and is done by applying heat until the soil reaches 180oF (82oC) for 30 minutes. When temperatures are raised above 212oF (100oC), most of the soil borne organisms are killed and the soil is considered sterile. Gardeners can pasteurize homemade potting soils using a kitchen oven; however, a long-lasting earthy odor can develop in the oven. To pasteurize soil, preheat the oven to 180oF. Then fill a pan with about 4 inches of moist soil and cover it with aluminum foil. Insert a candy or meat thermometer to monitor temperature and place the pan in the oven. When the thermometer reads 180oF, leave the pan in the oven for 30 minutes longer, then remove it and allow the soil to cool. Seeds can then be sown in the soil, or it can be used as a transplant medium for seedlings. https://extension.psu.edu/how-to-pasteurize-medium-and-sterilize-containers-and-tools

 

[natale]

You could try to sterilize the soil.

Thank you Mary.

I'm realizing that most of the soil I used is from last year. I try to be conservative wherever I can, as indoor gardening can add up in costs. Do you think I could let the soil dry out a bit so I can easily remove the top to salvage some seedlings, then pasteurize the soil in the oven in batches for reuse? Probably clean the pots while I'm at it?

I just hate to waste. Part of why I try to grow my own food is because of reusing by planting scraps or cultivated seeds. I've just never had to work around the issues that come along with limited indoor gardening.