In the last few weeks of flowering, buds keep filling out and small mistakes can cost a lot. Humidity that was fine in early bloom can now lead to bud rot. Overfeeding can leave very dark, clawing leaves. And harvest timing affects how mature the buds are when you cut. This guide walks through what to watch, what to change and how to decide when to cut. It draws on hemp research from NC State Extension, Oregon State University Extension and University of Vermont Extension. As always, check your state’s home grow law before you start a grow.

How to tell you are in the final stretch

Most photoperiod plants flower for roughly eight to ten weeks after the switch to 12 hours of darkness, but this varies a lot by strain. Autoflowers follow their own clock from seed. Signs you are in the last weeks include:

• Pistils (the hairs) darkening and curling in.
• Buds filling out and getting denser rather than growing longer.
• Older fan leaves fading to yellow as the plant moves nutrients into the flowers.
• Trichomes turning from clear to cloudy under magnification.

Use weeks after the flip, not just looks

NC State Extension notes that judging harvest by trichome and pistil color alone “is rather vague,” and that “increasingly, seed companies and breeders recommend harvesting based off of weeks after floral initiation.” NC State explains that “cannabinoid production and accumulation is so tightly regulated by the plant’s genetics” that counting weeks is “a more objective means of harvesting.”

For home growers, that means writing down the date you switched to 12/12 and comparing it with the breeder’s stated flowering time. Then use the plant itself to fine tune the date.

Read the trichomes

NC State Extension describes how “trichomes start off clear and turn an opaque white when maturing. After that the trichomes start to turn amber.” Because they “do not mature at the same time,” NC State’s best guess for hemp grown for CBD was to harvest when about 20 to 30% of the trichomes have turned amber. That is a hemp finding. Growers commonly use the same color sequence as a visual cue on cannabis, but it is not a universal harvest rule. You need a jeweler’s loupe or a clip on phone lens to see it.

Look at trichomes on the buds themselves, not the sugar leaves, which tend to change color earlier.

Climate in the last weeks

Dense buds trap moisture, so humidity matters a lot now. Keep air moving through and around the canopy, and aim for lower humidity than you ran in veg. In its drying guidance, NC State notes that hemp should be kept “at 60% or less” humidity, and that after drying “you have to keep it dry or it will absorb moisture and may mold.” Growers often aim for something in the 40 to 50% range in late flower. That is common grower practice, not an Extension figure.

Keep temperatures moderate, too. Very hot rooms in late flower can fade aroma. Big swings between day and night can also push condensation onto buds.

Feeding in the last weeks

As flowers finish, plants need less nitrogen. Yellowing on older fan leaves late in bloom is normal and expected. Dark green, clawing leaves late in flower can be a sign of too much feed. Follow the label on whatever nutrient line you use, and do not chase every pale leaf with more fertilizer in the final two weeks. For background on what each nutrient does, see our feeding schedule for soil.

The final weeks: step by step

1. Count the weeks. Note your flip date and the breeder’s stated flowering time.
2. Check trichomes twice a week. Use magnification on the buds, not the leaves, and look at several sites on each plant.
3. Inspect for bud rot every few days. Gently part the densest colas and look for gray fuzz or brown, mushy spots inside.
4. Lower humidity and boost airflow. Add a small fan if air is still around the top colas.
5. Ease off nitrogen. Let older leaves fade naturally rather than pushing extra feed.
6. Keep the light schedule steady. Do not interrupt the dark period, since light leaks can stress plants late in bloom.
7. Harvest by plant, not by calendar. If plants finish at different times, cut each one when it is ready.
8. Plan the dry room in advance. Oregon State University Extension advises that for slow drying the room should be well ventilated, at about 64 to 70°F and 50 to 55% relative humidity.

What happens after harvest

The final weeks set up the dry. University of Vermont Extension explains that drying “boils down to removing water from plant matter by evaporating it into the air,” and that lowering moisture “inhibits growth of microorganisms such as mold.” Oregon State University Extension adds that “storing flowers in the presence of light, exposure to air and high temperature can negatively affect some cannabinoid concentrations.” Have jars and a dark, cool spot ready before you cut.

Troubleshooting the final weeks

Gray fuzz or brown mush inside a bud. This is likely bud rot. Cut the affected bud out well below the damage, bag it and remove it from the room. Do not smoke, eat or use moldy material, and do not try to save it. Wear a mask and gloves when handling heavily molded plants, then wash your hands and tools. Lower humidity and improve airflow right away.

Fan leaves yellowing fast in the last two weeks. Some yellowing is perfectly normal. If new growth at the top is also yellow, check runoff pH and your feeding.

Trichomes are all clear at the breeder’s finish date. The plant may need more time. Keep checking every few days rather than cutting early.

Foxtailing (new spires on top of buds). This can come from heat or too much light close to the tops. Raise the light or lower the temperature.

Seeds appearing in buds. A stressed plant may have produced pollen sacs, or pollen came from elsewhere. Check for male flowers and remove them carefully. Our guide on how to tell if a plant has been pollinated can help.

Next steps

If you are not yet at the final stretch, see our guides on moving from veg to flower and reading trichomes.

FAQ

How long are the final weeks of flowering?

Most growers count the last two to three weeks before harvest as the final stretch. The exact length depends on the strain’s stated flowering time, so count the weeks from your switch to 12/12 and check the plant itself.

Should I lower humidity in late flower?

Yes. Dense buds hold moisture, so lower humidity and steady airflow help reduce the risk of bud rot. Many growers aim for about 40 to 50% in late flower, which is common grower practice.

What trichome color means harvest time?

Trichomes go from clear to cloudy to amber. NC State Extension’s best guess for CBD hemp was to harvest when 20 to 30% of trichomes have turned amber. That is hemp research, not tested on home grown cannabis. Check buds, not sugar leaves.

Is it normal for leaves to turn yellow before harvest?

Some yellowing of older fan leaves is normal in the last weeks, as the plant moves nutrients into the flowers. Yellowing at the top of the plant is worth checking.

What should I do if I find mold on buds near harvest?

Cut out the affected bud well below the damage, bag it and remove it from the grow space. Throw it away and do not use it. Wear a mask and gloves, then lower humidity and improve airflow.

Sources

• NC State Extension, Visual Guide to Floral Hemp Maturation. https://hemp.ces.ncsu.edu/visual-guide-to-floral-hemp-maturation/ (opened 2026-10-16)
• NC State Extension, Hemp Harvest Timing and Drying. https://hemp.ces.ncsu.edu/hemp-harvest-timing-and-drying/ (opened 2026-10-16)
• Oregon State University Extension, Post-harvest processing of hemp flowers. https://extension.oregonstate.edu/catalog/post-harvest-processing-hemp-flowers (opened 2026-10-16)
• University of Vermont Extension, Drying and Curing Herbs and Flowers. https://blog.uvm.edu/cwcallah/2021/02/23/drying-and-curing-herbs-and-flowers-hops-hemp-and-everything-else/ (opened 2026-10-16)