How to achieve perpetual harvests with cannabis

Perpetual cannabis harvesting means having several plants at different stages of growth (early, medium & late life) so that there is a repeatable supply of harvest-ready cannabis plants at regular intervals. You can do this with photoperiod feminised cannabis seeds, requiring two tents (one for veg, one for bloom).

Or, if you use autoflower seeds, you can enjoy perpetual harvests with just one tent and several plants at different stages of growth all under the same light schedule (typically 20/4). If you’re a medical cannabis grower or simply a connoisseur recreational grower that doesn’t want to see your jars run empty, then perpetual cannabis harvests are a great strategy. Read on for precise instructions for both feminised & autoflower seed growers.

What does perpetual harvest mean?

Perpetual harvests using autoflower seeds is the easiest approach. Using just one tent with the standard autoflower light schedule (around 18-20 hours of daily light) allows you to have a seedlings, plants in late bloom and some half-way between. All in the same indoor grow room. This can be achieved simply by germinating a couple of new autoflower seeds every 25 days (or so) and harvesting the mature plants once they are ready.

Perpetual harvests using feminised seeds necessitates the use of two grow tents. That single reason (an extra tent, another LED, more required space etc) is the main factor that deters perpetual harvesters from using feminised seeds.

Feminised strains need one tent for cannabis vegetative growth, often with 18-24 hours of daily light. The other grow tent requires a 12/12 cannabis light cycle for the cannabis bloom phase. With this technique the grower simply transfers plants from their veg tent to the bloom tent and then germinates a new batch of cannabis seeds (or gets some more clones).

Whether growing with autoflower seeds or feminised seeds, perpetual harvests are a smart option for any grower that likes a steady stream of fresh buds. With autoflower seeds the smart indoor grower can enjoy perpetual harvests from a single indoor grow tent.

Can you achieve perpetual harvests outdoors?

Not really. But growers at/around Mediterranean latitudes can get up to 3 successive outdoor auto crops each year.

Unless you live at (or very near) the equator it’s not possible to grow successive crops from feminised seeds. However, many growers can get two, or even three, successive outdoor autoflower crops - local climate permitting.

Growers with short grow seasons (e.g. Northern Europe and similar latitudes) can cheat by starting their first autoflower crop of the season indoors, growing them for a few weeks, and putting them outdoors once the weather has warmed up sufficiently.

Similarly, the last autoflower harvest of the outdoor season can be protected from the worst of the weather by a tarpaulin cover, or similar. Those with greenhouses can use greenhouse heaters and (where possible) supplemental self-adjusting LED lighting to great effect and extend the effective length of their grow season.

Key supplies for a perpetual harvest of cannabis

Feminised seed growers

If you’re growing with feminised seeds, you will need 2 grow tents (or 2 grow areas):

• 1 grow tent for veg - complete with light (18-24 hours of daily light), carbon filter, extraction fan etc.
  
  
• 1 grow tent for bloom - with a more powerful LED light (12/12 light cycle), fan, filter etc. Usually this is larger than the veg tent.

It’s not worth the risk of using a veg tent without odour control. Often the veg tent, with shorter plants, can be smaller with a lower power light compared to the bloom tent light. The flowering tent tends to be larger than the veg tent to accommodate monster plants.

Autoflower seed growers

• 1 grow tent - complete with powerful LED, carbon filter, extraction fan etc.

Using a fixed period of around 18-20 hours of light each day, you just need a single grow area to cultivate autoflower plants of all ages. This maximises convenience and minimises equipment cost for the perpetual harvest grower.

Autoflower plants of all ages and sizes can be comfortably grown together in a single tent. If any shorter plants need more light, they can be easily placed on top of a bucket/stand. In a typical 1.2m x 1.2m / 4ft x 4ft indoor tent you could comfortably accommodate a couple of large harvest-ready plants, a few mid-life autoflowers and a couple of seedlings. After each harvest, another couple of autoflower seeds are germinated.

Does perpetual harvesting cost more?

It depends. If you are growing feminised cannabis seeds you will need two tents, both with lights, fans etc. So inevitably you will use more energy than a single-tent feminised seed grow. But your reward is a harvest every 8-9 weeks.

For most growers, electricity costs are an unavoidable cost-of-growing. Comfort yourself in the knowledge that your homegrown weed is far better, and cheaper, than that bought elsewhere. Even with the energy costs included.

If you are growing from autoflower seeds you only have a single grow tent to power. However, it will probably be running all year round. A grower with a 1.2m x 1.2m, 4ft x 4ft indoor grow tent will typically be running around 400W of LED for 90% of the time.

Whether you’re a home grower or licensed-pro, there are certain costs that are difficult to avoid: nutrient costs, energy costs and cannabis seed/clone costs.

Why autoflower seeds are best suited for perpetual harvests

Perpetual harvest cannabis growers (often commercial growers) historically had no choice other than to use feminised seeds or regular seeds. They also had no choice other than to use two grow rooms.

The arrival of high quality autoflower seeds was a complete game changer for many perpetual harvest growers. Often these were commercial growers, and they leapt at the opportunity to use both their bloom room and veg room for production of high-THC weed.

Cannabis perpetual harvest step-by-step guide for autoflower seeds

Assuming a typical 1.2m x 1.2m, 4ft x 4ft tent with a good quality LED grow light. Typically, around 400W in power. Here we assume a 75 day grow cycle from autoflower seed to harvest.

• Step 1. Germinate 2-3 autoflower seeds. Some use small 1-2 litre containers and gradually transplant them into large containers. This can help with efficient use of floor area. More cautious growers will germinate seedlings in their final grow containers, perhaps around 12-15 litres in capacity. Wait 25 days.
  
  
• Step 2. Germinate another couple of autoflower seeds. You should now have a few plants at 25 days old and some new seedlings. Wait 25 days.
  
  
• Step 3. Germinate a couple more autoflower seeds. Your tent now contains plants at 50 days old, 25 days old and some new seedlings. Wait 25 days.
  
  
• Step 4. Germinate a couple more autoflower seeds. Your tent now has plants at 75 days old, 50 days old, 25 days old and some new seedlings. You can now harvest the 75-day old plants or give them an extra week if needed.

Simply repeat the process, harvesting a couple of plants every 25 days and germinating another 2-3 autoflower seeds at the same time. It’s a simple process which means you need never run out of weed again!

If you have a larger tent, you can accommodate more plants and will need to germinate more seeds than the 2-3 suggested above.

One useful tip, in the event of short plants requiring extra light, is to lift them to a higher elevation. Placing them higher on a small stand (e.g. on an upside-down bucket) ensures the plant will sit nearer the optical sweet-spot and receive higher light levels. Smaller seedlings tend to be shorter, further from the light and will receive much lower PPFD light levels than the mature blooms nearer the light.

Cannabis perpetual harvest guide for feminised seeds

With feminised seeds you will need 2 grow rooms/tents. In one you will have plants in veg getting ready to be moved into the bloom room, once it is available.

After you harvest the feminised strains in the bloom room, you transfer the plants from your veg tent into the bloom room. At that point you may also want to germinate more feminised seeds to put in the veg tent, where they will have up to 8-9 weeks to grow until the bloom tent is free once again.

One other option is to keep a couple of special mother plants in the veg room and use them for clone production. Mother plants can be kept alive for several years with the right care.

Perpetual harvest: grow unlimited weed!

Never running out of cannabis again is the main reason that so many home growers use a perpetual harvest grow. Buy autoflower seeds and organise your grow according to the 4-step plan above and you will always have fresh buds going in the jars from just a single tent!

Once experienced, many growers comment on how intuitive and natural (just like cannabis low stress training) it feels to have regular, predictable harvests of top quality weed from perpetual harvests using autoflower seeds.

For many, it’s easier and more convenient than having 2-3 traditional separate harvests. The only downside is that your grow room will be on and running all year round, with energy usage considerations. Many will accept these costs as a legitimate, unavoidable cost of growing with the bonus of regular harvests every 25 days or so.

Other tips include:

• Use of aerated grow containers, such as airpots, felt-sacks or similar produces a more oxygenated root zone and healthier, larger, plants.
  
  
• Use of slow-release organic nutrients allows you to grow your plants adding only water for much of the time. This so called ‘water-only’ methodology greatly simplifies matters, allowing your plants to grow in the nutrient sweet-spot free from the yield/quality limiting effects that result from over/under feeding. BioTabs are market leaders and highly recommended!
  
  
• Check the strain description carefully from your chosen autoflower seed supplier. If your strain takes longer than 75 days, you can adjust the timings in the 4-step guide accordingly (perhaps waiting a few days longer than the suggested 25-day interval to germinate new autoflower seeds)
  
  
• If you’re on a budget check out the Dutch Passion cannabis seed sale. Get some of Dutch Passion’s top strains for bargain prices and enjoy your next grow!