First time growers frequently:
Overwater their medium based plants. When you pot your plant, judge its weight dry by hefting. Then, water the plant thoroughly, until water runs through the drain holes. Heft it again. When your pot feels as nearly as light as it did dry, its time to water again.
Overfeed their plants. As MrSoul says, beginners rarely under do anything. When all else fails, follow the directions on the fertilizer bottle.
Overanalyze their grow. A first grow is like a first born child: you pay attention to every little thing that happens. Further, you worry at the first sign something may be wrong. Pay attention to what happens in your grow, but do not try and find a remedy for every yellow leaf. Frequently, the remedy of flushing your medium causes more problems than it solves. Be responsive when things go wrong, but be conservative in your remedies.
Overspend on grow supplies. New growers frequently commit themselves to unrealistic and expensive first grows. It is much more efficient to learn to grow and then invest in high end equipment rather than the other way around. Most experienced growers don’t have room for all of the grow paraphernalia they aren’t using.
Talk about their grow. Don’t tell anybody that does not have to know. How can you expect anybody else to keep a secret that you cannot.
Things to avoid:
1. Don’t Overwater
Overwatering kills marijuana plants. Water once the top few inches of the soil dries out. Hydroponics is harder to over-water than soil, due to the abundance of water roots.
2. Don’t Tell People
Why? They will only be jealous. People love to feel important and that is why they will tell other people; because others will listen to them. Keep it to yourself.
3. Touch/kill Germinating Seeds
It can take up to 10 days for a seed to sprout. The paper towel method is not recommended because you must handle the seeds when transferring them from the paper towel to your growing medium.
4. Grow seeds from seeded marijuana (hermaphrodite seeds)
Unless you are prepared for possible disappointments don’t use “unknown” seeds. This is why people buy seeds from seedbanks. Self-seeding MJ is produced from hermaphrodite plants or a very stunted and late flowering male the grower did not notice. Flowered hermi seeds will produce tall late flowering females coupled with early flowering males.
5. Don’t Over-fertilize
Fertilize after first 2 spiked leaves appear. Start with 25% of recommended label strengths and work your way up. If the leaves suddenly twist or fold under, Leach and Spray with pure water for several days! Don’t fertilize your plants every time you water! (Soil) A common watering schedule is to fertilize at full strength, then water at half or quarter strength. This prevents excess salt buildup, leaf and root burn. In addition, don’t water at full strength if the medium is too dry – root burn can occur. As a precaution, leach the plants with lots of pure water every 2-4 weeks.
6. Don’t Under-fertilize
Under-fertilizing is less common. If you prefer to give the plant ‘just enough nutrients’, use a organic soil mixture with blood meal and bone meal or some slow release fertilizer with micro nutrients.
7. Don’t Start with Clones
Start with seeds. Bugs are a pain, as are plant diseases. Many growers are able to grow indoors without pest problems for years. Another grower’s cuttings are almost guaranteed to have diseases &/or pests.
8. Don’t Provide A Bad Environment
Always provide air circulation and fresh air even during the night cycle. All the air indoors should be replaced every 5-10 minutes. Humidity between 30-70% temp aim for around 75-85? Even seedlings need a gentle fan to strengthen the stems.
9. Don’t Harvest Too Early
25% of the weight will form in the last 2 weeks. Begin flushing with 100% pH’d water when the pistil are 25% brown. Harvest when the plants have totally stopped growing and the white pistils are at least 50-75% brown. *NOTE: Outdoors if security is a factor make your own call on when to sacrifice the fields. Also take buds continuously in case of thieves.