Slow, slow seedling growth, mildew gnats?

jasminehearted(8)February 14, 2013

Hello All,

I wanted to be really brave this year and start a variety of plants from seeds. I have peppers, tomatos, and a variety of flowering plants like lisianthus, begonias, and sweetpea.

I'm having a terrible time - I do as much research as I can and I try so hard, but only the water propagated weed like plants seem ok (rosemary, wandering jew, creeping jenny). I have a light about 8 inches above a covered tray (mostly blue wavelengths, it's a daylight bulb). They are planted in seed starter and I started them early January.

They aren't leggy, they just don't seem to grow at all. Some seem a bit yellow. I try to keep the humidity in there pretty good - watering when dry and the light stays on them from 8am to 9pm to simulate summer light.

Also, I have INSANE amounts of mildew gnats. I suspect they are the problem. I hand kill them every day - literally I sit there and squish them for like 20 minutes, but I can't stop them (can I?). I started the plants inside, so they must have been in the seed starter soil itself... Many seeds never sprouted and the sweetpea seems most devastated by the larva, though I have two robust looking sweetpea seedlings in spite of it.

Only the tomatos and peppers seem to even be getting close to forming the second set of true leaves. Some plants sprouted within days of planting only to look exactly the same for like three weeks.

Is there any solution for me? I'll post pictures later today or tomorrow when I can upload them. Thank you.

Thank you for reporting this comment. Undo
digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Several possible problems.

First the covers are for germination only, not growing on. Covers, if used and many don't, should be removed as soon as the seeds germinate. Failure to do so results in far too much humidity, root root and leaf yellowing, damp-off fungus which leads to stem rot, stunted growth, severe fungus gnat infestations, etc. Air circulation is vital for healthy seedlings.

Second, once the cover problems are corrected, the light is too far away. 1-2" above the tops of the plants is the norm.

So you need to uncover, dry things out, reduce the humidity, stop over-watering (water only when the soil knuckle deep is dry) and set up a small fan to increase the air circulation. Tthe fungus gnats should all die off once things dry out a bit. If they don't then get some Bt (Bacillus thuringiensis) sold in several different forms including what are called Mosquito Dunks, dissolve in water to water the plants with a couple of times to kill the gnats.

Hope this helps.


    Bookmark   February 14, 2013 at 5:19PM
Thank you for reporting this comment. Undo

Also.......Lisianthus and Begonias are very very slow growing, they stay tiny for a very long time. You should see some growth the first month, but it wont seem like much. Begonias are the one thing that you do leave covered for a while after they sprout, but you cant keep the soil drenched.

    Bookmark   February 14, 2013 at 5:57PM
Thank you for reporting this comment. Undo

Thank you for the help. Here are the photos.

Part of why I left them covered so long was the fact that I had everything in one modular tray. It seemed easier to let everything stay covered since the begonias and such hadn't sprouted yet.

Now that everything is out the the soil I can put little clear cups over the begonias and lisianthus to give them a bit extra humidity while they establish and allow everything else to dry out.

    Bookmark   February 14, 2013 at 7:38PM
Thank you for reporting this comment. Undo

Yeah.... I live in a condo without any proper space for me to sprout the seeds... I put them by the screen door so they could try and get some of the ambient natural light in addition to the lamp.

I get NO direct sunlight from anywhere but I figured maybe some of the ambient UV would supplement the lamp since it's just a daylight bulb, not a proper full spectrum one.

    Bookmark   February 14, 2013 at 7:41PM
Thank you for reporting this comment. Undo
digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Part of why I left them covered so long was the fact that I had everything in one modular tray.

Easier, true but not what is good for the plants. For future reference mixing multiple different plants within the same tray is never a good idea. Needs and germination times differ greatly. It is a common question, frequently discussed here and a lesson everyone learns the first time out.

Ideally each variety gets its own container. The solution if one uses one of those kit trays is to separate/cut the six packs/nine packs apart so as they germinate they can be removed. Never leave them covered once they germinate.

As to the begonias, millions are grown annually without cover so continuing to cover them once germinated is your choice. Since you already have fungus gnats, I wouldn't. If you feel they need more humidity then just mist them lightly or keep a bowl of water sitting near them. Either way the soil needs to be dried out more.


    Bookmark   February 14, 2013 at 7:51PM
Thank you for reporting this comment. Undo

For fungus gnats or any other flying insect problem, buy some yellow sticky strips (called white fly strips in garden centers) and hang or lay them near plants. Be careful, though, they are very sticky and will peel paint!

You will be amazed at how many bugs get stuck on them!

    Bookmark   February 20, 2013 at 6:26PM
Thank you for reporting this comment. Undo

I'm going to try and find some of those sticky things, I keep forgetting when I'm at the store.

I uncovered my tray and unfortunately a bunch of the more tender seedlings died within about a day and half (the really teeny slow growing ones, UGH!)

I removed all the stronger seedlings like the peppers, sweet pea, and tomatos, and left the baby ones in there until they get more leaves. I put them in moisture control potting soil and set them in the only west facing window I have (upstairs). They actually get OK direct afternoon sun there. They were all kind of turning yellow, so I hope the high quality potting mix will feed them a little and they'll re-greenify. I only just barely watered them in the transplant so as not to drown them.

I've put new seed in the empty tray slots to try and re-grow some of the plants I lost - they dried out and died so fast and they had taken so long to sprout! Oh well, I have until late March or April in my zone.

One day I'll get this right!

    Bookmark   February 21, 2013 at 9:11AM
Thank you for reporting this comment. Undo
digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

I uncovered my tray and unfortunately a bunch of the more tender seedlings died within about a day and half (the really teeny slow growing ones, UGH!)

Please don't make the mistake of assuming that they died because you removed the cover. The most likely cause was root rot and/or damp off due to overly wet soil. Use of such humidity domes/covers is strictly optional and seldom if ever used by experienced growers because they tend to cause more problems than they prevent.

They were all kind of turning yellow, so I hope the high quality potting mix will feed them a little and they'll re-greenify.

Yellowing of seedlings is caused by too wet soil and the root causes.

You might want to note for future reference that many report such problems when using the moisture control potting mix. While it may work fine for well established plants, most find it keeps the soil too wet for young seedlings.


    Bookmark   February 21, 2013 at 3:02PM
Thank you for reporting this comment. Undo

Thanks Dave,

I'll remove the cover. I'm one of those sorts who tends to baby things... God only knows how many orchids have died at my hand... I swear I really do try.

The seedlings didn't seem to damp off, I've done that to so many plants in the past that I feel it looked different. They shriveled up - and these were green ones. A few came back when I watered them. They are currently in seed starting mix. This is the new set up. When I was transplanting I was actually very pleased with the roots I saw in spite of the gnats and my helicopter gardening. They were lush and strong, and longer than the greenery by double (which I read was good, since roots should develop first, and greenery after...? Is that why they seem to grow to slow to me? hmm)

I'm going to do everything in my power to water the transplants only as needed.

    Bookmark   February 21, 2013 at 3:48PM
Thank you for reporting this comment. Undo
Edie(5 NY (Finger Lakes))


I noticed that the lamp reflector in your picture is round. Can you tell us more about the light you are using? In other words, is that an old-style incandescent? A cfl? Something else? One bulb? Many?

A saying I've seen many places is that "You are not a gardener until you have killed something." Congratulations, you are now a real gardener.

If you want to try something that doesn't require additional light, read up on WinterSowing. There's a forum here, with detailed FAQ's. Wintersown seeds are planted in covered containers outdoors and don't sprout until the weather is consistently warm enough. I start many plants that way, but I grow indoors under lights too. Most wintersown plants in my zone wait until April or even May to sprout. I get desperate to see green well before then. So every year I start seeds for something that needs long months of indoor care, so I have something to nurture / torture through the long winter. ;-)

I second the use of mosquito control products for fungus gnats. I keep a metal tea ball in a watering can. The tea ball holds a few of the mosquito "bits" or a quarter of a "dunk" and keeps the crumbs from clogging the spout. I replace the dunk periodically. I keep the watering can filled and use that to water anything that needs a drink, all winter.

I ask about the light because I suspect you haven't got enough light on your seedlings. I don't think that western window is going to be enough either. I've killed many seedlings thinking that winter sunlight filtered through window glass would be enough. With what you've invested in seeds, potting mix, trays, and time, it makes sense to get proper lights. You'll also want a timer and a power strip. Look for a timer that accepts a three-prong plug. Plug the timer into the wall, the power strip into the timer and the lights into the power strip. Now you can run up to six lights synchronized on one timer.

My preference is for fluorescent tubes. So far the plants are happy as well. Two of the two-bulb shoplights, or a single four-bulb fixture, are necessary to light a standard flat of seedlings. A single shoplight isn't wide enough and the plants at the edges will stretch and lean in. With four of the 4' bulbs side by side you can light two flats. I learned the hard way that if I have room for two flats, to only sow one flat with seeds. Half a flat would be even better. I'm working on my restraint. Once the seedlings in the first flat grow and need to be potted up into larger quarters, that extra space is necessary to keep them all lit.

I use the 4' size because they're easy to find (I got a pair of fixtures free through Freecycle) and the 4' bulbs come in at the lowest price, most options, and most readily available. Fluorescent tubes come in different diameters. T stands for Tube. T12 is the fattest, T5s are the skinny sort found in many "grow lights." I use T12s because I already have the fixtures. If you're light-shopping, T8s are highly recommended on the Growing under Lights forum. "Cool White" bulbs work fine.

Get them very close to your seedlings as digdirt said. You'll need to be able to adjust the height of either the lights or the trays as seedlings grow. If your household includes anyone with waggy tails, poking paws, or grabby fingers then you will want the lights mounted securely and both lights and seed trays out of reach. If that's not an issue, you can carefully prop them on something, but remember you're dealing with thin glass.

Do check the temperature as well, and check it against the preferred ranges for each plant you're growing. Any accurate thermometer with the correct range will do the job.

Good luck!


    Bookmark   February 21, 2013 at 3:55PM
Sign Up to comment
More Discussions
When to uncover seedlings?
I've successfully started seeds for years by bottom...
Thank you All
I've been on GardenWeb forever, but I lurk mostly,...
patchworkfarm (z6 CT)
Conjoined twin basil seedling
This might be pretty common and not worth making a...
arlene_82 (zone 6 OH)
Germination time for Lily of the Valley started indoors
As a newbie, this is my first year starting plants...
preventing algae/moss
I have very small fans blowing gentle air across my...
Sponsored Products
Essentials Celebrations Gold and White Wall Clock
$48.95 | Bellacor
Home Decorators Area Rug: Tendril Natural and Cocoa 5' 9" x 9' 2"
Home Depot
Regency Fountain
$1,410.00 | Horchow
Bella Stainless Steel 5-quart Programmable Slow Cooker
Nautilus Planter - Small
Grandin Road
Nourison Indoor/Outdoor Area Rug: Nourison Rugs South Beach Aqua/Brown 10 ft. x
Home Depot
Fareast Gray Outdoor Pillow
$69.00 | FRONTGATE
Safavieh Poolside Grey/ Beige Indoor Outdoor Rug (9' x 12')
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™