CannaGLAP
Grow cannabis in Littleton, CO
Growing cannabis in Littleton: a harvest that dries too fast in 41 percent air
Littleton's fall is kind to flowers and hard on the finished crop. September and October average about 41 percent humidity, low enough that bud rot pressure stays light, and dry enough that a branch hung in an open spare room can turn brittle before it ever cures.
You spent four months growing that plant. How many days are you giving it to dry?
Adults 21 and over: yes (residents). Plant limit: 6 per resident, 3 or fewer flowering; 12 per residential property unless local law allows more.
Enclosed, locked area not openly visible; separate locked space if anyone under 21 lives there; local rules can be stricter. Source: Colorado home grow laws; 12 plant cap: HB 17-1220. Local rules (landlords, HOAs, city codes) can add more; this is a summary, not legal advice.
Indoors in Arapahoe County: dry air at both ends of a run
Begin at the end, because that is where the dry air costs the most. Drying wants slower air than this town supplies in fall. A dark closet or a spare tent, a small humidifier on a humidistat set near 60 percent, and a fan that stirs the room rather than blowing on the buds all slow things down. When the small stems snap instead of bending, the jars come next.
Seedlings feel the same air. June averages about 40 percent humidity and July about 37, so a fresh clone in a downtown apartment near Main Street loses water through its leaves faster than its new roots can replace it. Keep clones under a dome for the first week, then run a small humidifier in the tent through early veg.
Heat is the summer job. The Marston Filter Plant station, 2.7 miles away and 5,610 feet up, logs about 15 afternoons of 90°F or more in July, 9 in August and 7 in June. July nights cool to about 60°F, so from June through August the lamps belong in the overnight hours, with the dark period across the afternoon.
Winter turns the job around. December and January lows sit near 20°F, and about 147 nights a year reach freezing. A basement or garage tent chills fast once the light shuts off, so run the light through the coldest hours, keep pots off the slab, and give the tent a heater on a thermostat.
Heater safety: use one with tip-over and overheat shutoff, plug it straight into a wall outlet (not an extension cord or power strip), and keep it a few feet from tent fabric and plants.
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 46 | 47 | 55 | 60 | 69 | 81 | 86 | 85 | 77 | 64 | 53 | 45 |
| Avg low °F | 19 | 20 | 28 | 35 | 44 | 53 | 60 | 58 | 49 | 37 | 28 | 20 |
| Humidity % | 67 | 40 | 37 | 44 | 40 | 41 |
Highs and lows: NOAA 1991 to 2020 normals, Marston Fltr Plt station (2.7 miles away). Humidity: Open-Meteo historical model data, average daily humidity in 2024, for the months shown. Planning averages, not a forecast.
Your Littleton outdoor window
Colorado lets residents grow up to 6 plants each, no more than 3 of them flowering at a time, and caps a residential property at 12 unless local law allows more. Every plant has to be in an enclosed, locked space that is not openly visible, and if a person under 21 shares the house, the plants need a locked space of their own. Local rules in Littleton or Arapahoe County can be stricter, so check them first.
If you have a space that qualifies, start seeds April 7 to 21; plants go outside on May 19, two days after the safe frost date of May 17 and the day nights first average 45°F. A typical first frost waits until about October 11, but an early one arrives by September 27, which leaves about 131 days. Pick autoflowers or photoperiod plants bred to finish by late September.
| Last spring frost | May 2 in a typical year, May 17 to be safe (later only 1 year in 10) |
|---|---|
| First fall frost | Oct 11 typical, as early as Sep 27 (1 year in 10) |
| Frost-free season | about 160 days |
| Nights stay 50°F or warmer | Jun 5 to Sep 11 |
| Start seeds or clones indoors | Apr 7 to Apr 21 |
| Move plants outdoors | May 19 or later |
| Season note | Frost can arrive before mid October here: long flowering plants may not finish outdoors |
Your drying notes, kept to yourself
Western Welcome Week, the Wine Walks and the Candlelight Walk all fill downtown Littleton, and a town of about 46,000 is small enough that you may end up trading grow tips with someone you met between Sterne Park and the light rail station. How much of your harvest you describe in that talk should be your call.
Canna GLAP scrambles each grow entry on the phone itself, before upload. Someone who forced a way into our servers would turn up grow records nobody can read, and nothing to unlock them. The drying schedule that saved your last harvest is yours to keep or to share.
What is encrypted: your plants, notes, photos, feed logs and harvests. What is not: account details (such as your email, name and plan), a grow name or town if you type one, your team, and your sensors' names. The full list: what a hacker would get.
Questions growers in Littleton ask
Do I need a dehumidifier to grow cannabis in Littleton?
Seldom in flower. September and October average about 41 percent humidity, so a humidifier for clones and for the drying room usually earns its place first.
When can I plant cannabis outside in Littleton?
Move plants out on May 19, after the safe frost date of May 17 and once nights average 45°F. Seeds go in from April 7 to 21.
How late can I harvest outdoors in Littleton?
Plan to finish by September 27, the date by which an early first frost has already arrived. A typical year holds off until about October 11, but a plant timed for that date is taking a chance.
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