Yes, they do. Use the lights 12-14 hours each day for most tropicals. To a limited extent you can compensate for lights that are a little dim by providing a couple of extra hours light. Beyond about 16 hours, plants can start to suffer. Some species are worse than others. Many seedlings and a few mature plants do well under 24 hour light but I don't know if this will work indefinitely.

what type of plants? some need a rest period others can go 24 hours straight.

Are you asking if they need darkness at night or a rest period during the winter where you reduce watering and fertilizing?

Since everyone else assumes you mean darkness, I will say that in nature plants do not get light for 24 hours around the clock, so I wouldn't recommend keeping the lights on 24-7. It's just a waste of electricity and money. My plants get 8 hours of darkness each night and 16 hours of light, unless they are daylight sensitive and need longer or shorter daylight hours, then you adjust accordingly.

thank you everyone for your help
however i really meant the winter dormancy period, that normal unlit houseplants need and i wondered if they need it under lights
i should have been clearer
but this information is really helpful aswell thank you

Many tropical plants do not need a winter dormancy, they just keep on growing so long as it is warm and bright, there are no majore seasons in the tropics. That's why many of them make great houseplants. Some of them are strongly seasonal because of things like dry season dormancies but I'll assume you're not talking about that stuff.

So theoretically you can keep right on pushing through the winter. But watch out for trying to make a plant grow when there is too little light in winter, it will stretch and become inhappy. Also, look out for some plants that might have a photperiod response, maybe to trigger flowering. Even tropical plants might need a slightly shorter day length just to let them know what's going on.

I suspected you were asking about winter dormancy. On the houseplant forum, they say you should give all plants (unless they are winter bloomers) a rest during winter by reducing watering and not fertilizing, but I find that my plants keep growing year-round even when I've stopped or reduced fertilizing. If your temps are on the warm side and light levels are good, most will keep growing. With tropical plants, I reduce fertilizing to once a month at 1/4 strength and they still put out new growth. You may want to do the same with your tropical plants. Just observe your plants. If a plant is not actively growing, it may want a rest, so in that case I'd give it one.

ok thank you very much for all of your help
just to say my anthuriums havnt stopped flowering and my cycas revoluta is sending up a new throw of leaves :D
thanks again

Hello all and Happy Holidays!(being politically correct)
I've posted this question in the pepper forum also but thought I'd also post here, becuase you folks are so smart!
I'm doing vegies indoors this year, under hid lighting. All is going well but today I noticed that my serrano is showing some darkening/brittleness on some leaves, it's not just confined to the edges of the leave either. If it were just confined to the lower leaves I wouldn't be too concerned but I see some leaves are effected in the mid section as well...Speaking of too much light, I'm giving them 18 a day and everything else in the garden seems to be thriving. The serrano looks very healthy other than this condition. They are in well drained soil and I feed high quality organic liquid nutes.
Any ideas? Too much light? Too much nute? I've never experienced this outdoors in the garden. The plant is approx 10" tall and is ready to be re-potted but I don't think being in too small a pot would cause this?
Any ideas are appreciated! I've got a new digi that should be here tomorrow and I'll post pics if I can figure it out...
Thanks folks....

JW,

"...my serrano is showing some darkening/brittleness on some leaves, it's not just confined to the edges of the leave either. If it were just confined to the lower leaves I wouldn't be too concerned but I see some leaves are effected in the mid section as well."

Well, I would be concerned even if it were just the lower leaves. Everything about your plant's appearance communicates to you the state of its health and nutrition. The darkening makes me suspect a phosphorous deficiency. This is what a phosphorous deficiency in corn looks like. I don't have a link to a similar picture for a Serrano pepper.

"They are in well drained soil and I feed high quality organic liquid nutes."

I have to admit that I am not that enthusiastic about organic nutrients for culture under lights. Do you have an analysis of your organic nutes that you can post here, so that we can determine how much available phosphorous they have?

Also, what source of water are you using? I prefer to use rainwater or melted snow. Otherwise you need an analysis of your water supply and you run the risk of salts accumulations from the water itself.

Hope you get your digital camera soon so you can post some pictures of your plants. We should be able to tell more then.

MM

Hello,
I don't have an analysis but I can tell you that I use these same ferts. outdoors in the garden each summer on everything with fantastic results. I let my water sit uncovered for days before watering so that should eliminate the chlorine and salts. Actually I think I got a bit heavy handed w/ the amounts of fert I used last feeding. One of the reasons I love oganics is because they are so forgiving, but indoors, in pots, may be a completely different story. I'm gonna back off and see what happens....I'll get the pics up asap.

thanks alot for the input.

Fern, no problem, glad we could help. :) I would fertilize any budding or flowering plants at the usual fertilizer rate. Btw, what color are the flowers on your anthurium? I've always wanted a bicolor (Obake), but I love them in any color. Lucky you, enjoy your flowers!

Jwmeyer, it sounds like a nutrient problem (or over-fertilizing) to me as well. You may want to start a new post if you upload photos instead of in this post since I doubt it's a light issue. If you need any help getting your photos on the forum, let me know.

I don't use organic ferts. or any "special" water (rain water, distilled, holy water or whatever. lol) to water plants. :) I've always used regular tap water and never had any problem with it. If salt buildup is an issue, just let the water sit out overnight and flush your pots on a regular basis.

"Organic" of course tells us nothing about a fertiliser. It has no legally enforceable meaning in the retail context and is not the same as, for example, organic produce which is certified. So you may be getting a raw organic product like a corn meal or dried seaweed, you may be getting a highly processed product like a sewage sludge, or you may be getting a chemical fertiliser that comes from a sustainable source or is considered acceptable in an organic context. I wouldn't ever consider a raw product in a pot since the ecosystem to process it into nutrients isn't there. I put them on the lawn and let the bugs get to work. And I don't use the "chemical organic" fertilisers anywhere because they are more expensive than ones that don't have that word on the label.

S&B gets so technical..Which is not a bad thing, just technical...I use, what I think is not derived from sewage sludge..At least I hope not. The plants love it and growth is excellent, fruit set is excellent too. Here's the breakdown, maybe you guys can comment...
Metanaturals...Professional organic plant nutrient
Organic fertilizer w/chelated micronutrients and natural humic acids.
Guaranteed analysis:
nitrogen..........3%
water soluble nitrogen...2.4%
water insoluble nitrogen..0.6%
available phosphoric acid...3%
soluble potash....3%
It goes on to list magnesium, copper, iron, manganese, molydbenum and zinc.
Derived from, blood meal, feather meal, bone meal, potasium sulfate, magnesium sulfate, ferrous sulfate, copper sulfate, zinc sulfate, sodium molydbate, citric acid as a chelating agent.
Also contains humic acids...0.2% Derived from seaweed and decomposed plant and animal materials...
This is the vege formula.....So there it is....

What do you think?
Ps: does anyone else love these pop ups that appear right in the middle of the screen when your wrtitting or reading?

My experience says NO!

Cacti, succulents, Geraniums, Amaryllis, Daylilies, Balloon flowers to name a few I've grown 24/7 and all florished.

I've been growing under lights for years and have tried them all at one point. I've used timers and gone the whole route playing with day lengths, etc.

I now just use cool whites 24/7 and everything I grow does great. One additional I've added is wick watering when possible. I think a lot of it is in the expectations of the grower :) (Go Luther Burbank fans!)

I am currently experimenting with Balloon flowers under lights. See "Plant Propagation" and "Perennials Discussion and Gallery" for pictures, etc.

The experts say Balloon flowers only bloom the second year and only then after at least a 6 week under 40 degree period. My experience under lights and with wick watering is 10 weeks from planting seeds I have buds and at 12-13 weeks they start opening.

I also got some first year bloom from both daylilies and Amaryllis by starting under lights (24/7) and transferring them to the greenhouse when they outgrew my lights.

Just DO IT :)

John

please help me!!
do plants grow better and stay healthier undrer constant light(24-7) or do they need rest form light?

Been growing for years using 24 hours of lighting.....never once have I encountered a problem. Actually, I get shorter, stockier specimens and in about 1/3 of the usual time it takes.

I add that some plants....particularly those that flower in spring and late fall, need a night period or shorter day to initiate flowering but even with 24 hours of light these do fine.

"I am mother nature".....well at least in my greenhouse!

Well I have been experimenting a bit w/ the light cycle for my toms, peppers and eggplant...I originally had them at 18/6 and everything was fine. I have since changed to a 14/10 schedule to see if there would be a difference. Not a huge adjustment, but enough for me to notice that they seem to be looking healthier/less stressed. It could be the strain's I'm growing or other factors but they were growing so quickly @ 18/6, almost too fast...This change has slowed them down and I'm seeing better bud retention and larger fruit....I've always felt that most plants need some amount of dark period but this little experiment has further convinced me of that.