Weed seeds can survive in the soil for years before they germinate and grow. It typically takes between 3-4 months to grow weed. Let’s take a look at the question of how long does it take to grow weed and the time needed for each step.
How long do weed seeds survive in the soil?
CORVALLIS – Weed seeds can survive in the soil for years before they germinate and grow, according to Jed Colquhoun, weed specialist with the Oregon State University Extension Service.
Why should home gardeners care?
“If you combine the longevity of seeds in the soil with the fact that weeds such as common lambsquarters can produce over 500,000 seeds per plant, the incentive to hand weed your garden becomes much greater,” said Colquhoun.
“Prevention is the most effective form of weed control,” he said.
Here are some basics on weed seed biology:
Undisturbed weed seeds tend to persist longer than seeds subjected to periodic tillage. Weed seeds in deeply worked soil tend to last longer than seeds in shallowly worked soil. Seeds deep in the soil are “stored” below the germination zone.
Grass seeds tend to be less persistent than broadleaf weed seeds.
The number of surviving seeds of most weed species declines rapidly the first year. But thereafter the rate of weed seed decline slows. Some seeds can persist for decades.
As many as 130 million seeds per plow acre were found in a Minnesota study.
Different species of weeds have seeds that last varying numbers of years in the soil. The scientific literature provides some information about seed longevity, including:
- Brome grass seed seldom lasts more than two years.
- Annual ryegrass – up to nine years.
- Perennial ryegrass – up to three years.
- Annual bluegrass – up to about five years.
- Wild oats – three to six years, but longer in deep soil.
- Jointed goatgrass – three to five-and-a-half years.
- Barnyardgrass – up to 13 years.
- Quackgrass – up to four years.
- Common velvetgrass – 10 years or more.
- Mustards – are long lived. Seeds excavated from a monastery in Denmark were dated to be 600 years old and 11 of them germinated. More commonly, mustard seeds last for decades.
- Lambsquarters – may last up to four decades.
- Russian thistle (tumbleweed) – short lived, most live only a year.
- Wild carrot – several years.
- Curly dock – more than a decade.
- Canada thistle – more than two decades.
- Field bindweed – more than 50 years.
- Leafy spurge – at least a few years.
- Common groundsel – most die within a year.
Scientists found lotus seeds in Manchuria that germinated after over 1,000 years, said Colquhoun.
How Long Does It Take To Grow Weed?
How long does it take to grow weed is a very commonly asked question. Usually it takes about 3-4 months to grow the average cannabis plant – but with the right tools and strategy, you can grow the weed plant you want in as little as 8 weeks. Let’s take a look at the question of how long does it take to grow weed and the time needed for each step.
How Long Does it Take to Grow Weed – Growing Timeline
The timeline below lays out a seven-stage process of a typical grow schedule. If you’ve been searching online for “how long does it take to grow weed?” you’ve likely run into a range of time periods. Generally, a marijuana plant can take 14 to 32 weeks to grow, which translates into about four to eight months to grow. This is for growing a marijuana plant from seed.
The length of time it takes to grow a weed plant can be broken down into multiple phases from seed to harvest:
- Getting your equipment (1 day to 2 weeks)
- Getting your clones or seeds (1 day to 4 weeks) (12 hours to 8 days)
- Seedling phase (1 to 4 weeks)
- Vegetative phase (2 weeks to 6 months)
- Flowering phase (6 weeks to 3 months)
- Harvesting phase (1 to 3 days)
Step 1: Getting your weed growing equipment = 1 day to 2 weeks
If you know what you are looking for then this could happen quickly. We will help you with this later on as we set up the grow-rooms and do some grows with different styles and grow mediums.
Step 2: Getting your clones or seeds = 1 day to 4 weeks
Getting clones (cuttings from healthy mother plants) is easy to do in areas that allow cannabis cultivation. But in states or countries where it is illegal to grow, obtaining healthy clones can be a challenge. Seeds, on the other hand, can be ordered on the internet and generally take 2 to 4 weeks before they arrive by mail.
Step 3: Germinate The Seeds = 12 hours to 8 days
If starting with clones this can be skipped. The average time to germinate is 2 or 3 days. Make sure to check your seeds every day because seedlings can sprout in as little as one day. You’ll know your seed has germinated when your seed has popped and displays a tap root formation.
Check out our guide on the best method to germinate marijuana seeds using paper towels and water.
Step 4: Seedling Phase = 1 week to 4 weeks
Once again, can be avoided if using clones and not seeds. As your cotyledons begin to take shape, so will your cannabis leaves in a single leaflet form. Generally, growers can give their seedling a light amount of nutrients after the third set of leaves begins to appear.
Step 5: Vegetative Phase = 2 weeks to 6 Months!
Yes, that is correct. This stage in the plants life has a huge fluctuation in how long it needs to take. You, as the grower, hold all the power and get to choose how long this phase is. Once you change the light cycle that the plant receives to 12 hours of light, and 12 hours of darkness per day, the plants will switch to the next phase, which is flowering.
If you want to, you can switch the lights to 12/12 right away and force your plants to flower! The sooner you change to 12/12, the faster your plants will flower, and the sooner you can move on to the next crop. But, keep in mind, the less amount of time you keep your plants in the vegetative phase, meaning getting at least 18 hours of light per day, the smaller your plants will be, and the less marijuana you will have to use.
If you are concerned with how big your plants will grow, maybe because you only have a small space to grow in, you can grow cannabis that only grows only a few inches tall, and you could even grow it the entire time in a little plastic cup if you wanted to!
Keep in mind that buds do not form for at least 2 to 3 weeks in the vegetative phase when beginning with seeds. Most growers allow their plants to stay in the vegetative stage from a few weeks to a few months so they get big enough and will end up with a sizable harvest. Bigger plants produce more buds!
But, many growers choose instead to grow small plants and to harvest more often with smaller yields each time. We recommend at least 3 weeks or more in the vegetative stage with at least 18+ hours of light each day for optimal yields. Even 24 hours of light per day is sometimes better, with certain strains.
The more light, the more buds!
Keep in mind that cannabis plants usually double in size from vegetative phase to when they are done flowering. This means it’s sometimes best to change to 12 hours of light and 12 hours of darkness once the plants are one-half the size that you feel your grow room has adequate space for.
During the vegetative phase, you can use a number of cultivation training techniques such as super cropping, crimping, topping, tying, bending, sea of green (SOG), screen of green (SCROG), and trellising to alter the growth, direction, height, and quality of your crop.
Autoflowering strains, however, have a different vegetative time period than regular feminized seedlings. Autoflowering strains will have at least two to three weeks of vegetative growth before they automatically start showing any bud formations regardless of photoperiod.
Step 6: Flowering Phase = 6 weeks to 3 months
In nature, cannabis plants start to flower in the fall months, when they are receiving less light. The decrease in light signifies to the plants they are nearing the end of their life cycle and its time to begin flowering.