Indoor lighting drying out plants?

[emerald7]

There have been so many posts about using indoor lighting to grow plants that I'm thinking maybe there should be a separate forum about lighting.

Anyway, here is my question. I'm growing full-sun herbs indoors in terracotta pots in my dining room under a light (105W compact fluorescent, 6500K, equivalent to 400W of incandescent light). The plants are about 4-5 feet from the light, and the temperature is just under 70 where the plants are (69 point something). The soil has about 33% sand in it for drainage purposes.

A lot of sites say to leave the light on for 12-16 hours a day, because indoor lighting is not as good as real sunlight.

However, I have been doing this for about a week now (leaving the lights on 12-14 hrs a day), and I've noticed that having that light on for that long seems to really dry out the plants quickly... The soil in my plants is getting dry very fast, and they are getting droopy if I don't water them about every 36 hours. It is probably dry in here humidity-wise as well, because it hasn't been very humid lately and the heat system is on.

I am thinking that the terra cotta pots losing moisture, combined with the light and dryness, etc. is causing this, but does anybody have any thoughts? Are the plants supposed to get dry that fast? And, is this 12-16 hr thing really correct? I'm thinking maybe it should just stay at no more than 12 hrs for the light.

Thanks.

[rainbowgardener]

Yes, the 16 hr thing is really correct. Especially with the light 4' away from your plants! For starting seedlings I usually have the lights 4" away from the plants. Yes in a heated indoor environment plants do dry out. You might try setting them on a humidity tray (Its a tray you put pebbles in, then set the pots on top of the pebbles. Put water in the bottom, but not up to the level of the pots, so you are not watering the plant directly, you are humidifying the air around the plant.) You didn't say much about how you are watering your plants or what kind of soil they are in. If your plants are drying out that much, you might try setting them in a sink full of water and let them really soak up water for a few minutes (that would saturate the terra cotta too, which may be wicking water away from your soil) then drain the excess out. If your soil is drying out really fast, maybe it is too sandy. If you add a bit of peat moss to it, it would hold water better. But most herbs like to dry out a bit between waterings, don't want to stay moist all the time. You can always try misting the leaves a bit between waterings, see if that perks them up.

[emerald7]

Yes, the 16 hr thing is really correct. Especially with the light 4' away from your plants! For starting seedlings I usually have the lights 4" away from the plants. Yes in a heated indoor environment plants do dry out. You might try setting them on a humidity tray (Its a tray you put pebbles in, then set the pots on top of the pebbles. Put water in the bottom, but not up to the level of the pots, so you are not watering the plant directly, you are humidifying the air around the plant.) You didn't say much about how you are watering your plants or what kind of soil they are in. If your plants are drying out that much, you might try setting them in a sink full of water and let them really soak up water for a few minutes (that would saturate the terra cotta too, which may be wicking water away from your soil) then drain the excess out. If your soil is drying out really fast, maybe it is too sandy. If you add a bit of peat moss to it, it would hold water better. But most herbs like to dry out a bit between waterings, don't want to stay moist all the time. You can always try misting the leaves a bit between waterings, see if that perks them up.

I did mist them a little today between waterings and that seems to perk them up a little. I guess I will just have to make sure I water thoroughly each time, and mist a little in between... maybe I can try the humidity tray thing too. later when I transplant maybe I can change the soil composition

[emerald7]

You didn't say much about how you are watering your plants or what kind of soil they are in.

I'm just watering them with a typical plastic watering can, until the soil looks wet, or until a little water comes out into the plate under the pot. These plants are in a soil that's 33% coarse sand, 25% compost, 12.5% composted "peat humus", 12.5% composted cow manure, 17% potting soil, plus a little fertilizer.
There is also an inch of rocks in the bottom of the pot for drainage.

[applestar]

Because your plants are in clay pots (unglazed I assume), they'll need a bit more water than what you describe. Definitely water until it starts to drain out from below, but that bit will be sucked back up by the dry pot, so water again, about the same amount or maybe a little bit less. Check again in 15~30 minutes and see if the water is still in the tray. If there is, you've watered too much. If there isn't, you might want to give a little bit more.

After doing this a couple of times, you'll get a "feel" for how much each pot and plant need to be replenished.

[emerald7]

Because your plants are in clay pots (unglazed I assume), they'll need a bit more water than what you describe. Definitely water until it starts to drain out from below, but that bit will be sucked back up by the dry pot, so water again, about the same amount or maybe a little bit less. Check again in 15~30 minutes and see if the water is still in the tray. If there is, you've watered too much. If there isn't, you might want to give a little bit more.
After doing this a couple of times, you'll get a "feel" for how much each pot and plant need to be replenished.

Yes they are unglazed.
OK, I'll try this method.