perpetual cannabis grow

Ultimate Guide On How To Maintain A Perpetual Harvest

A perpetual harvest, also known as symbiotic rotation, is a method mostly used by commercial cannabis growers or avid smokers who don’t want to run out of cannabis and need a fixed harvest.

1. What is a perpetual harvest?

A perpetual harvest consists of having different grow tents containing plants in all stages, this way you never run out of buds because you’ll harvest plants on a schedule and have other plants ready to move and substitute the ones you’ve just harvested.

This technique uses multiple grow tents to make sure you have plants in the vegetative and flowering stage at all times with one tent running an 18/6 and the other one running a 12/12 light cycle.

Have in mind that almost every grower that does starts from clones that they took from their plants in the vegetative stage, this will allow you to save money on seeds but you will be stuck with the same strain, you can also start from seed but it can get expensive, either way, after your plants are in the vegetative stage, the process is the same.

Once your vegetative plants reach a certain height you can move them to the 12/12 tent or if your flowering plants are ready for harvest, you can move them from the 18/6 tent into the flowering tent.

2. What’s the cost of a perpetual harvest?

This method itself doesn’t require any special equipment but because you need two or more growing tents, you’ll have to double up on all equipment (like light, exhaust fan, fans) and that’s not all.

Because you have to maintain a temperature and humidity level, the electricity bill can go up, but it’s worth it if you are a commercial grower or if you benefit from the insane amounts of buds you’ll harvest.

3. Pros and cons


Scheduled harvest

Depending on the strains, plant size and number of grow tents, you can schedule your harvest from every couple of weeks to every couple of months .

By knowing when you’re going to harvest you can set up and prepare your drying room and even schedule your harvest for a weekend so you’re able to trim every plant with no hurry.

High yields

Because you’re growing in a couple of tents, you’ll have a lot of plants to harvest at a time and the yields will be huge .

Never run out of weed

With a perpetual harvest, you’ll never run out of weed and even if you do (which is really hard), you’ll probably have a harvest coming up soon so there’s no need to spend money buying flowers.


High cost

With more grow tents and growing equipment the cost will go up considerably , although it’s worth it for commercial growers, you’ll have to evaluate it if you’re a home grower.

Needs more space

The amount of space needed will depend on the number of plants you want to harvest at a time but either way, it will take more space than having just one, usually, growers use 2-3 growing tents so you’ll need a big room.

A lot of plants and weed

This is not actually a con per se but if you live in a place where cannabis is illegal it definitely is depending on the country, you can get in trouble with the police if you have professional growing equipment and a large amount of plants and cannabis.

4. Strain and timing

A big factor that will influence your harvest schedule is the strains you’ll be growing.

Photoperiodic strains may take 8-13 weeks from seed to harvest so having approximately when your harvest is gonna be is crucial, normally, you would grow just one strain at a time and how long it takes to flower would be your schedule.

So, for example, if your seeds take 10 weeks to flower you know you’re going to harvest in 10 weeks but if you grow more than one it can be hard to control, another good way is to have one strain per tent, so you have one strain flowering and another one vegetating to make it easier to keep track.

5. Perpetual harvest with autoflowering strains

If you want to spend less money and time or maybe learn how it works before investing in more equipment, you can have a perpetual harvest with autoflowering cannabis plants, because you don’t need to change the light cycle you can do this with just one growing tent.

This is because autos vegetate and flower under the same light cycle (18/6) so you can have plants in all stages in the same tent, the down side is you’ll have to germinate seeds every time you harvest.

When growing autos this way, the problem isn’t coordinating when you’ll move the plants to the flowering tent but controlling the height, because autoflowering cannabis are hybrids they can be Sativa or Indica -dominant and their structure and height will vary a lot so you’ll have to train them either with a trellis net like a Scrog or by tying down the branches so all of them receive the same amount of light.

6. Vegetative and flowering growing spaces

When you’re setting up the growing spaces for a perpetual harvest you need at least 2 growing tents (unless you’re growing autoflowering strains), each one of them must have an optimal environment for the stage the plants are in.

The vegetative tent must have a higher humidity (around 60%) and an 18/6 light cycle with a blue light spectrum while the flowering tent must have a relative humidity of around 45% and a 12/12 light cycle with a red spectrum.


Vegetative grow tent Flowering grow tent
To shorten the veg. Stage, grow smaller plants. Make sure your tent is light-proof, if there are light leaks they can become hermaphrodites .
It’s recommended you have one strain per grow tent to avoid problems. Have a carbon filter ready, a large number of plants will smell up the whole room.
Use weaker lights than in the flowering tent. Ensure you control the temperature and humidity to prevent getting bugs or mold . in the buds.

Because you don’t need more than one tent when growing autoflowers, you will have to adjust the environment in your grow tent as your autos grow, have in mind the appropriate temperature and humidity can vary from strain to strain but you can use the same as for photoperiodic cannabis and adjust accordingly.

7. Perpetual harvest step-by-step

After you have your growing spaces set up you just need to start growing, by following these simple steps you can successfully run a perpetual harvest without hassle.

Step 1: Seeds or clones

First of all, you need plants. You can start a perpetual harvest with seeds or clones, starting from clones will take less time and will save you around 2-3 weeks, but if you don’t have a way to get clones you’ll just have to germinate the desired number of seeds.

Step 2: Let them vegetate

Although it’s not obligatory, it’s recommended you have one strain per tent, this way you avoid having problems, if you are vegetating different strains in the same tent, some may grow taller and overshadow the smaller ones, and you’ll have to train them.

Having the same strain means you’ll transfer all of them to the flowering tent at the same time instead of having to move one by one when they’re ready.

Step 3: Move them to the flowering tent

After your plants have reached the desired height, you can move them to the flowering tent, make sure you have plants to move into the veg. Tent also.

If this isn’t your first growing cycle, this is when you’ll be harvesting the plants in the flowering tent but if it’s the first you don’t have to worry about that.

It’s extremely important to clean your tents before moving your plants.

Step 4: Harvest and repeat

After your first harvest, you’ll have everything ready to continue your perpetual harvest.

When you harvest your plants, you’ll transfer more plants from the veg. tent to the flowering tent and you’ll have clones or germinated seeds ready to move into the veg. tent.

All you have to do now is keep moving plants from one tent to another when they’re ready and keep harvesting forever.

8. In conclusion

Perpetual harvest is the best way to keep your jars always full if you smoke too much or if you’re a commercial grower and despite being more world because of the number of plants, it’s worth it.

We hope this article helps you start your own never-ending harvest and if you are already running a perpetual harvest tell us how it’s going, please leave us a comment below!

A perpetual harvest is a way to have a scheduled harvest and is mostly used by commercial growers or avid smokers who don't want to run out of weed.

Perpetual Harvest Method: Ensure Multiple Harvests Of Ripe Buds Per Year

The perpetual harvest method can result in more weed than you could ever smoke. Read on to find out how to create a bud overload.


Growing cannabis using the perpetual harvest method means a continuous supply of buds. Doing a perpetual harvest just requires a little more space, some extra gear, and some good timing. Once you get into the flow of things, you will realise just how easy having a steady supply of buds can be.

At its simplest, the perpetual harvest is when one set of plants is harvested in a flowering space, then is replaced immediately by plants that have already completed vegetation in a separate space. The vegetation space is then replenished with freshly sprouted seed stock or clones. Once the timing is mastered, it is possible to ensure a harvest every 8–12 weeks depending on species flowering time.


Vegetative and flowering cannabis plants are exposed to different types and amounts of light. With the exception of autoflowers, it is impossible to have infant and mature plants in the same area. The solution is having two separate growing spaces, or a single growing space split into two in some fashion. Two rooms, two grow tents, two cupboards, you get the picture—in perpetual use, one for vegetation and one for flowering.


The perpetual harvest experience has two distinct advantages. First and foremost is never running out of weed. With many contemporary hybrids, maturing time is only around 8 weeks. This means a fresh batch of replacement nuggets every two months. Being caught out with no weed and resorting to buying it can be a real bummer and burn a hole in your pocket pretty quickly. So with a little extra effort and good timing, rapid turnover can mean 6 harvests per year.

Second is disaster insurance. If something goes bad in the flowering room and a crop is lost for any reason—such as pathogens like bud or root rot, accidental poisoning from a nutrient or pH mistake, etc.—then there are quick replacements available from the veg space and you don’t have to go right back to the start. Losing a few weeks is tolerable, but losing 10 weeks or more of work is heartbreaking.


There are added costs of course—not doubled though, as plants in the vegetative phase require less of everything to grow well. Smaller pots in a smaller space under weaker lights, like T5s for example, require fewer resources to maintain. But they are still extras, and there will be an increase in power, nutrients, and grow medium costs to consider. The added setup cost with all the hardware balances out in the end when the jars are overflowing, all the time.

It goes without saying that perpetual harvests mean additional time requirements from you, the grower. Maintaining twice as many plants will require your extra attention with each stage. A perpetual vegetation chamber will typically demand regular topping and training, or other actions that promote vigorous growth. But who doesn’t enjoy spending time with their plants?

Whoops, too many buds! Perpetual harvesting can often mean lots of buds leftover when a new harvest is dried and ready. This opens up some exploration doorways into the many uses of cannabis. Extra green can mean that edibles, hash, and any number of extractions become a part of your repertoire.


Create two spaces. By nature, a smaller vegetation space is needed, while a larger flowering space allows plants plenty of room to stretch.

Of course, the size of each space is relative to the room available. A small and a large grow tent are awesome if you have a spare room, but a cupboard with a light-sealed smaller space within it serves the purpose just as well. Configure each chamber appropriately for vegetative or flowering growth.


The first crop will take a standard amount of time for a veg-to-flower grow, but once the first vegetative cycle is complete, you are in full-swing.

  • Create plants for the vegetation chamber either from seed or clones. When they are appropriately sized, place them into the flower chamber.
  • Immediately prepare more plants—clones or freshly germinated seeds—to refill the vegetation space.
  • After 8 weeks of loving care, the flowers will be ready for harvest again, with replacement plants ready to go.


Depending on the size of your setup, beginning another cycle can be done in an afternoon.

  • Harvest existing plants in the flower space.
  • Remove pots and clean the area.
  • Fill flower space with the plants from the veg space.
  • Refill vegetation space with new stock from seed or clones.
  • Begin again, and so ad infinitum.

Perpetual harvests need two areas operating simultaneously so fresh plants can be cycled through when they are ready. Try these hints for an efficient setup.


  • During the vegetative phase, plants are smaller and take up far less space and resources. As such, a lower area with less-intense lights than the flowering area will do, such as a raised shelf in a cupboard for the flowering plants to sit on, with the veg chamber below.
  • If separating a space into a two-in-one setup, ensure that each is light-tight from the other. Light pollution during the flowering lights-off period can cause poor flower growth, swap plants back to veg, or stimulate hermaphroditism.
  • Consider a number of smaller plants, rather than only a few big ones. This shortens the vegetative phase while still filling up the grow space with a reasonable canopy.


  • The flowering area must be completely light-proof. Again, light pollution can damage your hard work.
  • Heat and humidity control are equally important, especially in smaller spaces, as is vigorous air circulation. Too hot or too cold can affect proper bud formation, while high humidity and poor air circulation can encourage mould. Get the right gear for your situation and a robust oscillating fan.
  • With cannabis, contemporary high-terpene hybrids in particular, the smell can be very strong. If discretion dictates odour control, then make sure extract fans and carbon filters are all working properly.


Timing is key, and this comes with experience, especially experience with your selected strains. When flowers are harvested, you want ideally sized veg plants to put in the flower space right away. Getting appropriately sized plants at the right time means knowing about strain characteristics. Some might grow so quickly that a full 8 weeks isn’t needed for veg, and the veg chamber can be rested for a while. Some may need the full 8 weeks to get to an acceptable size for the 12/12 flip—it’s a pheno wonderland out there.

Strains with a shorter flowering time are ideal for the perpetual harvest method. Many contemporary strains will mature in 8 weeks, and 8 weeks is enough time to get well-vegged plants. An 8-week harvest also means a refill every two months, which is a lovely turnover.

If you do want to grow longer-maturing sativas like the Hazes, for example, then the harvest frequency drops to 4 per year because of the 12-week flowering time. This also means less time is needed for the vegetation period, and money and time are saved while the veg area rests.

Alternatively, you could change the light schedule to 12/12 in the veg chamber when plants are big enough and give them a flowering head start, moving them over to the flower space already pre-flowered. Then, you can simply change the veg space lights back to 18/12 and prepare a new batch of plants.


Separate spaces aren’t needed for autoflowering strains, as young or mature plants are all exposed to the same light regimen. So squeezing some infant plants in the spaces between older plants, or around the circumference where light is weaker can give them a head start.

The complete life cycle of many auto strains is only 8–10 weeks, so needing a veg space becomes irrelevant. You can grow from seed to flower in the same amount of time as perpetual harvests. Most contemporary autoflowering varieties have a cannabinoid content in line with photoperiod seed cultivars, so there is no need for concern on quality.

In addition to the quick turnover of autoflowers, there is also another way to speed things up if you’re dealing with feminized photoperiod strains. When seeds are only given 12 hours of light right from germination, they go immediately into flower. The complete vegetative phase is bypassed, resulting in more controlled heights. Flowering from seed also means no veg space, but a number of cannabis species don’t like the treatment very much.


With two appropriately kitted out growing spaces, or an equally well-appointed cupboard and some extra hours spent in the grow-op, the perpetual harvest can see any grower with more buds than they need every 8 weeks. It is an ideal way to try a number of different strains in a year, and find ones that suit your setup and suit your mind!

The perpetual harvest system of growing cannabis can return up to 6 harvests per year. Find out more at Royal Queen Seeds.