Switching to MH last weeks of flowering?

Been reading a couple things about people switching back over to MH the last 2-4 weeks of flowering causing increased resin production and more compact buds. Anyone have any experience with this. Currently running 600w HPS in a 3x3x7 tent, 2 weeks into flowering, just wanted to get ahead of the game and see what everyone else thinks. Thanks in advance guys!

Never have done it personally, had a close friend try it and he said he felt like his buds were more frosty but got a decrease in yield. He said it wasn't worth it and he wouldn't be doing it again.

a lot of people think it helps with trichome development and ripening. But it doesn't. Changing the spectrum during flower at any time will cause growth to slow and lagg for a week or 2. The plant goes through a spectral transition and takes that week or so to adapt to the new spectrum..

the sun never changes spectrum. You want the same spectrum through veg and flower. A broad even spectrum. Mh during veg, hps during flower, mh at the end, it is a marketing scheme to get you to spend more money.

707humboldt said:

Never have done it personally, had a close friend try it and he said he felt like his buds were more frosty but got a decrease in yield. He said it wasn't worth it and he wouldn't be doing it again.

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hyroot said:

a lot of people think it helps with trichome development and ripening. But it doesn't. Changing the spectrum during flower at any time will cause growth to slow and lagg for a week or 2. The plant goes through a spectral transition and takes that week or so to adapt to the new spectrum..

the sun never changes spectrum. You want the same spectrum through veg and flower. A broad even spectrum. Mh during veg, hps during flower, mh at the end, it is a marketing scheme to get you to spend more money.

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Thanks for your input gentlemen! Will not be switching anything out, was just curious. CHEERS!

I have 2 tents , on 1 tent I start with mh, for 2 weeks then to hps, then the last 2-3 weeks back to mh ....it does increase trichromes, most resent harvest 10.6 oz on to plants lots of resin,my other tent I go straight thru with 1 bulb either mh of hps depending on what I'm growing

I'm interested in this, but I may just try 1 or 2 Days of MH before 24 hour darkness before harvest

Anyone have anymore info on this? I always thought mh in veg and hps in flower... I have done dual spec as well and just mh not seeing much of a difference

you'd be better off adding some UVB for resin production in my opinion. i use the 10.0 reptile bulbs.

sunpulse has a 10K MH bulb they say to use at end of flower. never tried it myself.

I thought it worked for me i waited until after my plants put on the bulk then the last couple weeks I'd switch it i figured it had something to do with a full spectrum i also let my plants go for a long time

rkymtnman said:

you'd be better off adding some UVB for resin production in my opinion. i use the 10.0 reptile bulbs.

sunpulse has a 10K MH bulb they say to use at end of flower. never tried it myself.

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i didn't care much for running my uvb all day i was always afraid of doing more damage then good

KarmaPaymentPlan said:

i didn't care much for running my uvb all day i was always afraid of doing more damage then good

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the more UVB, the more trichomes to protect the plant. unless you get above the level of the sun or some outrageous amount.

I am doing just that on my current grow, but I can thus only give my small-sample, newb observation. This is my third grow. The first two I did MH all the way as that is what my offline mentor uses and suggested to me. So many here said I should be using HPS for flower so this grow I started my flower with HPS. At around day 50 I thought my plants had noticeably less trichomes than previous grows. I switched back to MH. Now at day 73 and almost ready to chop (also taking longer to finish--previous grows of same strains were well-done at 70 days.). I am close to normal in trich generation. Cannot tell you whether the HPS would have ultimately got me there, but it didn 't seem like it was going to. I find it hard to believe a spectrum change confuses and slows things. That said, next grow I veg with MH and I am going with an HPS augmented with UVB and blue T5s.

depends on the amount of uvb output. Less than 5% run all day. 10% run for 5 hours a day. 15-20% run 2 hours a day.

dont go getting 20% uvb reptile bulbs. 5% is plenty of uvb. The plants will produce trichs as a defense mechanism to protect the plant against harmful rays, insects, and some predators so to speak. Light also degrades trichomes. But the trich's replenish while the plant sleeps. Sort of like skin cells. Anyway too much uvb can degrade a plant.

make sure to always wear glasses around UVb .

any hid bulbs with UV won't work in an air cooled hood with glass. When UV passes through glass it converts to infrared lighting.

partly why philips CMH bulbs are quartz crystal coated and rated for open reflectors.

Not sure about switching between them but i have used mixed spectrums with success. During bloom phase I currently use a combo of HPS and LEDs for supplemental lighting but in the past I have run both a HPS and mh simultaneously which caused heat issues but also produced some very dense & frosty bud.

hyroot said:

depends on the amount of uvb output. Less than 5% run all day. 10% run for 5 hours a day. 15-20% run 2 hours a day.

dont go getting 20% uvb reptile bulbs. 5% is plenty of uvb. The plants will produce trichs as a defense mechanism to protect the plant against harmful rays, insects, and some predators so to speak. Light also degrades trichomes. But the trich's replenish while the plant sleeps. Sort of like skin cells. Anyway too much uvb can degrade a plant.

make sure to always wear glasses around UVb .

any hid bulbs with UV won't work in an air cooled hood with glass. When UV passes through glass it converts to infrared lighting.

partly why philips CMH bulbs are quartz crystal coated and rated for open reflectors.

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Yeah, I have a CMH setup on my wish list now that I know more about them. (Thx 4 that) Running a 600w digital (quantum) now and have bulbs for a couple years so a bit reluctant to spend the $. Sometimes its nice to be a newb as there are so many areas of improvement. Oh wait!!! I think we need some porn. ...see, not ready

add a supplemental 250w metal halide to half side of the tent and see if it makes a diff. i will be running this test next cycle in my new cab with the main lighting being a 400w HPS.

If it doesn't have any benefit, fk it - I will have a cloning/baby veg/mother lamp

Thanks for all the great feedback, I wish I could take the time to respond to each of you individually but at the moment I have been working too much and need to get some sleep. I ordered a Zoo Med Reptisun 10.0 26w UVB bulb and will be adding it to my grow next week. Since Im using a cool tube I am loosing a lot of the UV light already so this seems to be the best option! Happy Growing Guys!

slinger36s said:

Thanks for all the great feedback, I wish I could take the time to respond to each of you individually but at the moment I have been working too much and need to get some sleep. I ordered a Zoo Med Reptisun 10.0 26w UVB bulb and will be adding it to my grow next week. Since Im using a cool tube I am loosing a lot of the UV light already so this seems to be the best option! Happy Growing Guys!

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good choice. make sure it's in an aluminum not white reflector. i always shut mine off when i'm working in the garden. can give a nasty sunburn/hurt your eyes.

rkymtnman said:

good choice. make sure it's in an aluminum not white reflector. i always shut mine off when i'm working in the garden. can give a nasty sunburn/hurt your eyes.

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One step ahead of you bro, got some Grow1 GRUVE Glasses Grow Room Ultra Violet Eliminators. Gotta protect them eyes boys! Also picked up a 10 in reflector for the bulb, aluminum, not ceramic.

rkymtnman said:

you'd be better off adding some UVB for resin production in my opinion. i use the 10.0 reptile bulbs.

sunpulse has a 10K MH bulb they say to use at end of flower. never tried it myself.

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Exactly mh has a percentage of uvb rays and hps has no uvb rays at all which is why experience growers switch from hps to mh for the last 2 to 3 weeks cause of the UVB rays that the mh carrys