Heat. Just read some Ask Ed this weekend. Days over 85. Even though the plants can live, and even thrive in high heat, 90-100+ make for stringy plants... like Sativas. Maybe the real 'changes' to the land-races that we know.
Bad light makes them 'stretch' but, bad light will give you airy buds... but bad, airy buds to boot.
I live in a tropical climate and the above is right. The main cause is heat. We can grow some nugs the size of your fist but they are gonna be foxtailed if its a good strain. Otherwise they would die of mold most likely. I've never heard of bad light, but if the light is to far you can also get airy buds.
IMO the cause for airy buds has been overcrowding. My last grow was cool - about 70 to 75F but the plants were crowded.
They grew tall and stringy with airy buds.
I think it's the plant itself. I've had crops (that were all one strain) and had airy budded plants, right next to it's thick tight giant bud sister. So it may be heat, it may be poor lighting, or it may just be shit luck...
I read somewhere someone mentioned that any stress will stunt growth. Anyone believe deficiencies can create plant stress that contribute to this? And is temp itself the issue, or rather stress, as the result of high temps? Just wondering if staying as stress-free as possible would contribute much to correct the issue.
In my experience...heat is a big one...also the strain. sativas are good for this...cutting early as well a mostly sativa strain would need more then a regular 8-9week indica strain. mostly sativa strains have gotten nice and nuggy if given the proper time to mature for me. sativas are a bitch.
Sativa genetics will give you airy buds. But don't despair because they will light up your brain. A lack of light especially on lower budsites will give you airy buds too.
I'm not sure if there is just one cause. I have recently gone from fluff to nuggs. I seriously upgraded my 3'x3'x4' flower room from a 430 watt HPS to a 1000 watt hps, added an AC , CO2 and water chiller. Rez temps are a constant 68, day temps are 85, nite temps are 68. All these combine for a perfect environment for my girls and they thank me with huge, solid nuggs. Even at 48" below the light at the base of the plants. And that's true for my sativas, indicas and hybrids.
CovertCultivatr, did you aggressively clear out leaves so the lower nodes could have more light and give you your dense lower nuggs? I was running a 1kwatt in a 4x4 growing branches the length of my arm. Top 25-30% was prim-o bud while the rest was fox-tailing very airy (and at times, paler) bud despite insane resin production. I did not clear out leaves.