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My aloe
My aloe  
Flowers with gnats
Flowers with gnats  
QUESTION: I have been on google over 4 months and am finally coming to you for help. I noticed today you were answering many questions on lots of different sites and thought you would be the person to ask. I moved to Cincinnati with my boyfriend and started buying a few plants, at first I bought rosemary and sage which were very small and were growing well in our kitchen window.  I then purchased a Kalanchoe and was given a couple of baby spider plants which I rooted in water that I changed every 3-4 days and my friend gave me an aloe plant. Well now I needed to repot all of my plants, so I bought a bag of generic potting soil, I don't even know what kind now, at a local discount store simply because it was the amount I needed and I happened to be there with a friend, I have MS and don't drive. I had purchased a few plastic pots in October on clearance and repotted my plants in November. Well within a couple days I noticed gnats, I thought it was the dirt. So I bought a bag of Miracle Grow and was lucky enough to get a decent afternoon to take them outside and once again repot my flowers. I took every plant out of the dirt, rinsed them all down to the roots, washed out all the pots, threw the old dirt into the woods behind our house away from my work, I even washed the windows. At first all was well I was so proud to have rid our house of those pests, but within a week or so I saw more gnats so I got online and tried sugar water, a drop of dish soap and yellow food coloring, I put in clear glass bowls, rocks glasses and candle holders anything I could get my hands on, see I also have OCD and try to keep our house immaculate and now I have gnats everywhere. I resisted the urge to water because I also saw that might help break the mating cycle and we left over Xmas for 2 weeks. When we returned I didn't notice any gnats, I believe they only move at certain times of the day and are attracted to light because I am constantly looking in the dirt every time I walk by. Now on our return home I give my plants a much needed drink and I have sprouted gnats again. When I first started getting gnats my boyfriend warned me the house was prone to get them in flowers, he said he brought home a couple of Poinsettias years ago when the church was finished with them and noticed gnats and threw them away and they died off. I've done everything I've read to do, we even bleach our drains, no standing water in dishes fruits and veggies are all in the fridge, it's only the plants that I love and want to keep so badly. I can see them crawling around the dirt, but they are tiny and fast, I kill several a day, and they are starting to go to rooms without plants and are rather annoying. We have over a foot of snow and it's very cold, I can't take them out, I was lucky they survived the first wash and repot. The plants look good just thirsty. I've been fighting this since November and am at my wits end. Now I have put out sugar water with fresh squeezed lemon in it  and have the bowls around all flowers and even sitting in the pots around the flowers, please help me save my plants and my sanity? I haven't saw any eggs, only the little yellow balls that I couldn't possibly believe a tiny gnat could lay and I read it was a slow release fertilizer in MG, I've even picked what I could get of those out of the soil and they only seem to be at the top of the dirt but it seems they multiply somehow even without water.

ANSWER: Hi Lisa,

There are three issues here. One, is unnecessary repotting. A second is lack of quality control with bagged potting soils. Third, is all of the amateurish and mostly incorrect information available on the internet.

Unnecessary repotting is the most common of all plant care mistakes. The vast majority of plants do best when kept quite potbound. Over-potting usually leads to pest problems and root rot. In addition, most folks do not know how to properly repot. For example, it is NEVER  a good idea to rinse away the soil from the roots. That damages the tiny root-hairs that everyone ignores, but that do most of the work. Had you not repotted, you would not have the problems you do now.

Just because you use a popular name brand does not mean its potting mixes are any better than other brands. Indeed, their potting mixes are quite notorious for harboring fungus gnat larvae. Unfortunately, there are no standards that potting soil companies have to subscribe to, so you usually don't know what you are getting unless you read the fine print that lists the ingredients. Avoid potting mixes that include bark chips, soil, humus, compost or moisture control ingredients. The ingredients should be limited to peat moss, perlite, vermiculite, sand and coir. Any other ingredients are likely to harbor gnat larvae.

Virtually every one of the various methods you used to eradicate the gnats are not based on any rational information. They are nothing more than silly or poorly understood methods that are ineffective and posted by amateurs.

Fungus gnats are nearly always a sign of potting soil that is being kept too moist and causing roots to rot. Gnat larvae (the eggs are too tiny to see with the naked eye) feed on decaying organic matter. That includes compost, bark chips and rotting roots. The larvae live primary in the upper layers of the soil. As the larvae mature, they develop wings and fly out, so they need to be near the surface. The winged adults only live for about a week before dying of old age. So the key is to get rid of the larvae.

The most effective way to eradicate the larvae is to deprive them of the decaying organic matter they need. That means allowing the soil to dry out deep into the pot almost to the point where the plant wilts. (Some plants can withstand drought better than others). Your plants will also benefit from drying out more. Plants that are in pots that are too large take a very long time to dry out and that is when root rot sets in and gnat larvae thrive.

By repotting and rinsing away soil, you have done a lot of damage to your plants. There is no remedy for this past mistake other than to not make it again. I suggest that you remove as much soil as possible from the surface because that is where many of the larvae live. But don't expose the roots. Then, allow the soil to dry out as much as possible before adding just enough water so that it reaches that same level of dryness again within a week. If you follow these watering instructions and are very patient for a month or so, you should see a gradual decline in the gnats. Quick and easy solutions offered online are not effective.

I have written detailed articles on repotting and on treating plant pests that I will email for free to you (or anyone else) who emails a request to me at wcreed@HorticulturalHelp.com. I have also written an indoor plant care book in a PDF format that I can sell you if you contact me at my email address.

Please let me know if any of this is unclear or if you have any additional questions.

If this information has been helpful, please click the Rate Volunteer bar below and enter a rating and NOMINATION for me. I am a volunteer on this site so Ratings are the only compensation I receive for answering plant questions.

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or email me at wcreed@HorticulturalHelp.com or call me at 917-887-8601 (EST)
 
Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

Visit my website at: A link to HorticulturalHelp.com





---------- FOLLOW-UP ----------

Aloe
Aloe  

Aloe
Aloe  
QUESTION: I'd like to thank you for such a rapid reply! I'd just like to be clear on the directions I have trouble with comprehension sometimes do to the MS. I only need to remove the dirt 1 time and then water lightly once a week so they would be as dry as the previous week. Now I'm seeing your point by having an oversized pot I'm giving the gnats more than I'm giving to my plants, a reference that came to my mind are children's shoes you don't buy them 3 sizes to large and wait for their feet to grow. The plants that seem to have the most gnats are the spider plants in the larger pots, my Kalanchoe and Aloe seem to not be bothered by gnats but I did barely water them because the Aloe root was maybe an inch and a half and the Kalanchoe roots less than that. To be fair I did put the aloe in a much smaller pot than the 1 my friend gave it to me in. So by rinsing the plant down to the roots thinking I was ridding myself of gnat larvae I was only hurting the plant, but would you recommend in a couple of months, when it warms up here, I leave the root area alone and go back to smaller pots with the recipe you gave me so this won't happen again? Are there any premixes you would recommend, am I adding to the problem by putting out the sugar and lemon water dishes or does it matter? One other concern I did have was my aloe, the ends seem to be yellowing and curling in is this the one plant getting to little water she told me very little water, lots of sun. So I've only watered it a tiny amount every 2-3 weeks as I told you the root is small and she wasn't sure there was enough there when she gave it to me but there is a new center spike that grew so I figured the root wasn't an issue. Thank you for all of your help, maybe my thumb will eventually turn green.

Answer
Hi Lisa,

Thank you for the rave review! It is much appreciated.

Yes, you only need to remove the loose soil from the surface once. You do seem to understand abut watering, which is really about allowing the soil to dry out properly. Your analogy to over sized shoes for kids is apt.

Aloes, Kalanchoes and other succulents survive drought very well and should be kept drier than most other plants. That means they are growing in an environment less habitable for the larvae than your Spider Plant which require soil that is kept moister.

Although your plants would have been better off if they were in smaller pots, I don't recommend repotting to smaller pots now or later. Just be very careful with the watering so the soil dries out properly.

Premiere's Pro-mix is a good packaged potting mix if you can find it.

Adult gnats are attracted to sweet liquids and the color yellow. Some fall in and drown. But they are all going to die in a week anyway, so why bother? Concentrate on the larvae in the soil.

Your Aloe is still a baby with a tiny root system. That is why it is a bit disfigured. In good light and with proper watering (allow the top half of the soil to dry completely before watering), new growth that comes in should be healthy.

Green thumbs are learned and earned; they are not a genetic condition. I'm sure you will achieve yours.

~Will  

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Will Creed

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I am the only expert in this category with professional hands-on experience and knowledge of all indoor plants. I can answer questions regarding light, water, fertilizer, repotting, pruning and humidity and temperature requirements. I can identify plant pests and provide information on safe, effective treatments. My answers are based on 35 years of professional experience and scientific research and are clear and easy to understand. I do NOT use search engines to find answers to your questions. If you read my previous posts here, you will get a good idea as to how thorough and professional my answers are.

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I have over 35 years of professional indoor landscaping experience caring for plants in homes, offices, building lobbies, stores, restaurants, and other adverse environments. I have written extensively on the care of indoor plants, including a 260 page book. My specialties include Ficus trees, low light plants, repotting, pest control, and re-blooming holiday plants. Be sure to check my ratings and nominations to learn why I am the top-rated indoor plant expert. I am the only House Plant expert consistently ranked in the AllExperts Top 20.

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BA, Amherst College

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