Originally Posted by green_grow
is it a good practice to put a screen on one's intake(s) ? i am thinking of something like cheesecloth; might help keep bugs out, right ?
also, how long can you keep seedlings under a floro until they need to be transferred to HID ? i know there are people out there using floros all the way, but for my first grow i want to go with hps. experimenting with floros can wait.
Yes, putting a filter on an intake can be good, just keep in mind the more restricted you make the air flow the lower you fan's CFM (cubic feet per minute of air exchanged) will become. So I'd find a good fine mesh or screen but just do one layer. I would think cheese cloth would do. Also on a related note, if you are running something like a cool tube where the air might come in from outside and get passed thru the cool tube anb out the room without being exposed to the grow area, you should still consider filtering those too. Dust, insects and what not otherwise gets in and will dirty your bulb and the cool tube on the inside. At the least this will lower the efficiency in light output of your cool tube and require periodic cleaning, at worst the build up on the bulb could cause the bulb to explode (It would have to be pretty dirty for that though).
Now you're next question. There is no particular time limit, it depends on what you are doing and what results you want. Given you are working with fluoros and HPS, I would veg with the fluoros only and flower with the HPS. So in that scenario the time limit is dependent on how well your plants veg. Also depends on the strain and it's characteristics. A recent trend in indoor growing applies to sativa's everyone knows they flower longer and grow more in flower then indica's. This allows for fairly decent indoor results by flowering plants while very young, like two weeks or less. Essentially enough growth goes on in the early stage of flower that the plant can still manage to grow to a pretty decent size which ends up being just about perfect for indoors. So in that example the fluoros would be two weeks. Now I like to use fluoros to veg seedlings and clones. I typically grow what would be considered indoor bush/tree style in soil. At finish my plants stand about 6 to 7 feet tall. I can do this because I have 8 feet of vertical space in my grow room. This allows me to veg pretty much as long as I want so I just veg until they pre-flower so I can sex them without having to do anything special. This translates to mainly 6 to 8 weeks of veg minimum. Now I also like to use a 3 stage transplant method. 1 gallon to start, 3 gallon half way thru veg, 5 gallon just before flower. The timing on that usually has me in veg 8 sometimes 10 weeks. So like I said it depends on a number of factors. Basically when it comes to lighting it's about intensity and cooler tempurature. The more intense the light the further the light can penetrate before it grows too weak to do the plant any good. This is why HIDs are the prefered indoor light for flower because plants are usually too tall for fluoros to penetrate very far. You can offset this though by using lights on the sides as well as above the plants. The other factor, color tempurature, has to do with the light's spectrum. MH and cool whites are blue spectrum lights and is the light of choice for veg. HPS and warm whites are red spectrum and are the prefered lights for flower. So working with fluoros and an HPS this is why I say you should veg with fluoros and flower with HPS. Put your intensity where it will do the most good. However you should still ensure your fluoros are cool whites. Now red spectrum can also be used throughout the whole grow, the plant just won't grow quite as well. Not a major difference though. Same is true for blue spectrum, you can go the whole way like that if you have to but it won't be all it could be. Also you need to consider other things like, do you have enough fluoros to get sufficient veg growth? Successful results in flower are directly proportional to how strong, how leafy, and how well developed the plant is going into flower. The rule of thumb is if there is sufficient pot space a plant will grow two to three times it's height in flower, so if I want my plants no more then 6 feet I should flower around 2 feet. If all I have to veg with is one shoplight for example, then I'll likely not have a good plant going into flower. In that case I would want to either get more fluoros or if that's not possible, use the HPS for veg as well. If you get dependent on that though then you become stuck with one grow at a time rather then being able to veg some while others are flowering, so you have a new batch ready to flower come harvest time for the other batch. This would be a form of perpetual gardening. Some people like to do one crop a year so for them having the ability to veg and flower simultaniously might not be as important.
In a way it sounds like what you are really asking is how long should you veg? The standard time frame is at least until it reaches maturity by showing either alternating nodes and/or pre-flowers. This is usually 5 to 6 weeks. Again though, what lights to use, when, where and how long depends on a number of variables, your grow space, style, medium, ventilation, strain, goals, etc.