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When people ask, “When should I harvest cannabis?” they are usually asking one or both of two questions:
- What time of year should I harvest my cannabis?
- At what stage in the flowering cycle is the right time to harvest my cannabis?
To answer both questions briefly before we go into more detail:
- Harvest time depends on when you planted and whether you’re in the Northern or Southern hemisphere.
- The best time to harvest marijuana plants depends on its growth pattern (indica, sativa or hybrid) and how well the trichomes have developed (glandular hairs that contain cannabinoids and terpenes).
Read on below for more detailed information.
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How to Tell Cannabis Is Ready for Harvesting
It’s inaccurate to assume that a cannabis plant is ready to harvest just because it’s in its flowering period and has started to produce buds. The better way is to look at the color and development of trichomes.
- Clear trichomes –- The hairs are translucent and the plant is still producing resin in its glands. This is not the ideal time to harvest, and the plant’s cannabinoids and terpenes are not at peak concentration.
- Milky/cloudy trichomes –- This indicates that cannabinoid production is at its peak. A cannabis plant is usually ready to harvest when half of its trichomes are cloudy. This can result in a more uplifting, energizing effect for some users.
- Amber trichomes –- Amber trichomes tend to indicate that the THC/THCA in cannabis has started to deteriorate, meaning there may be more cannabinol (CBN) in the flower. CBN can have sedative effects, and many report feeling those effects with amber trichomes.
Many users like a mix of milky and amber trichomes, although the proportions of the split are down to personal preference. Some prefer all or mostly cloudy with few amber trichomes for a more cerebral effect. Others prefer closer to a 50:50 split between cloudy and amber trichomes for a balanced head and body effect. Others prefer 60% to 70% amber trichomes for a less stimulating, more sedative effect.
Healthy cannabis plants should be a vibrant green color. A color change to yellow or brown leaves is are a sign that the plant has some nutritional deficiencies or root rot. Feeding the plant too many nutrients (“overfeeding” or “nutrient burn”) is also a problem that can discolor and dry out the plant’s leaves. If growing in soil or a soil-coco mix, it is best to be sparing with nutrients and let the soil do most of the work.
If your plant is starting to brown after all the trichomes have developed the plant is probably dying. These plants should be harvested as soon as possible!
Different strains of cannabis can produce different bud shapes and densities. In general, cannabis buds are ready to harvest when they thicken and the white pistils start to darken.
Tips and Tricks for Harvesting
There are many different tips and tricks for harvesting, and these can depend very much on the growing environment and medium. Here are some tips and tricks that can help regardless of your growing environment:
- Do not feed the plant any nutrients in the last week of flowering. You will want to flush out all nutrients in the growing medium so it doesn’t end up tainting the buds.
- Low stress training (LST) can help increase yields and the vigor of the plant. LST is the practice of gently bending stems and tying them in place to increase the amount of bud production. Think of LST as “exercise” for your plant, where providing a little resistance can help it grow stronger.
- Pruning the bottom leaves during flowering can help the plant focus its energy on bud production.
- For those new to growing cannabis, pick a forgiving variety that is well suited to your environment. For instance, if you can only grow in small, indoor spaces in a cold climate, growing an equatorial sativa should be avoided.
Unless you’re an outdoor grower in a tropical or subtropical climate (or you’re growing indoors), where cannabis can be planted year-round, you will usually start growing cannabis outdoors during the spring months and harvest during the fall. In the Northern Hemisphere, the spring months are March, April and May, and the Fall months are September, October and November. In the Southern Hemisphere, the seasons are swapped.
In general, the spring and summer months constitute the vegetative period of growth, during which the cannabis plant establishes its roots and starts accumulating resources needed for flowering and reproduction. Flowering is triggered when the days start to get shorter, usually by the end of summer or beginning of fall.
Depending on location, 1 to 2 outdoor cannabis harvests are possible annually.
You can generally grow cannabis indoors year-round, although it is still wise to monitor the ambient temperature outside of your grow space. Hotter weather may require more fans, for example. People regularly growing indoors can expect 4 to 8 or more harvests per year, depending on how often they plant and what strain of cannabis they’re growing. This is called “perpetual harvesting.”
How Long Does It Take for Cannabis to Grow?
Cannabis growth is divided into four stages:
- Seed germination stage – Seeds start sprouting, usually between 7 and 14 days, although sprouting can sometimes take just a few days if the seeds are fresh.
- Seedling stage – lasts about 2-3 weeks. This is when the seed opens and the cannabis plant starts producing leaves, starting with small, round leaves (cotyledons), then serrated leaflets. As the plant develops, it eventually produces the digitate leaves we visually associate with cannabis.
- Vegetative stage – For 3 to 16 weeks, the plant starts to establish and grow stronger roots, stores energy and prepares for the flowering stage.
- Flowering stage – lasts about 6 to 16 weeks, depending on genetics. The first 5 weeks of flowering are when the plant starts to produce flowers and buds, and the rest of the flowering period is when the cannabis ripens. Depending on genetics, the plant is ready to harvest after 8 to 16 weeks.
The flowering period for both indoor and outdoor cannabis plants is generally the same, lasting between 8 and 16 weeks, depending on the plant’s genetics. Indoor plants usually have shorter vegetative periods, as plants can be forced into flowering by switching to a 12/12 cycle (12 hours light, 12 dark) within a few weeks.
- The flowering period for indica strains (varietals) is usually about 8 weeks, although some may have shorter flowering periods (around 6 to 7 weeks) and others longer (up to 12 weeks).
- Sativa strains, with plants that tend to be tall and lanky, can take between 12 and 16 weeks to flower.
- Hybrid strains/varietals are a blend of short, stout, quick-growing indicas and tall, thin, long-growing sativas, and can exhibit characteristics of both. Hybrids can take between 6 and 12 weeks to finish flowering.
Strains That Grow the Fastest
Cannabis indica and Cannabis ruderalis varieties tend to grow fast, usually ready to harvest after 8 weeks of flowering. Some varieties may take as little as 6 or 7 weeks, others 9 or 10 weeks. Some examples of fast-growing cannabis cultivars include:
- Lowryder, White Ryder, Hobbit and many other ruderalis-indica crosses
- Early Girl
- Red Dwarf
- Bruce Banner #3 Fast
- Speed Queen
Strains That Take the Longest to Grow
Sativa and sativa-dominant hybrids often take the longest to grow, usually taking between 12 and 16 weeks to reach maturity. Cannabis strains that can take a long time to grow include:
- Neville’s Haze
- Colombian Gold
- Chocolate Thai
- San Fernando Valley OG
- Malawi Gold
- Durban Poison
The Bottom Line
Knowing the best time to harvest cannabis is an art, and it can take a few tries to find out the best time to harvest a particular variety. You may also have personal preferences regarding how many milky trichomes and amber ones you want on your plant at harvest.
Frequently Asked Questions
How do you know when to harvest cannabis?
Cannabis buds are ready to be harvested when 50% or more of their trichomes are cloudy or milky.
How many months does it take to harvest cannabis from seeds?
This can depend on whether you grow indoors or outdoors. Indoors can take 3 to 4 months to harvest cannabis from seed. Outdoors is usually around 6 months.
How often can you harvest a cannabis plant in a year?
Many people think that you can only harvest a cannabis plant once. However, it is possible to harvest from the same plant twice or more by a process called “revegging” or “regeneration.”
To do this, you must prune for a bushy plant, not trim during flowering, harvest good buds a little earlier than usual (6 or 7 weeks instead of 8 or 9) keeping all the leaves and less-developed buds intact, feed the plant nitrogen throughout its flowering period, and then put the plant back on a 24 hour light cycle to revegetate. You will eventually be able to harvest again. This process is recommended for more experienced growers.
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