When to plant watermelons in Grand Junction: 6 May – 18 July

In Grand Junction, watermelon: sow for seedlings from 18 March to 20 June; plant into a greenhouse from 15 April to 18 July; plant out into open ground from 6 May to 18 July. For plants and seeds, the places nearby include Mesa Mycology Center (garden centre, 4 km) and Upland Gravel LLC (garden centre, 5 km); addresses and opening hours are below.

Watermelon in Grand Junction: soil, season and weather

In Grand Junction the soil, not frost, sets the date: the last frost is over around 18 April, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 6 May, 18 days later.

Last spring frost	18 April
Top 7 cm of soil at 18 °C	6 May, 18 days after the last frost
Into an unheated greenhouse	15 April – 18 July; April outside: 4.6 °C at night, 19.9 °C by day; card 18–35 °C
First autumn frost	27 October, 174 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	4 July – 15 September
Days left for picking	115
Daylight	12:55 on 8 April, 14:00 on 6 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, June, has 3 rainy days

The same dates in Grand Junction hold for Cucumber, Bell Pepper, Eggplant, Zucchini and Pumpkin.

Watermelon in Grand Junction: care after planting

Planted on 6 May: in the first weeks water every 5 days.

Feeding, by the card’s schedule from that day:

6 May — feed: balanced (NPK)

Pests and diseases of watermelon to watch for:

Dates count from the first planting day of the window above; a later planting moves them by as many days.

Weather in Grand Junction during the watermelon season

Days average above the watermelon card's 18–35 °C in July (35.1 °C). Nights average below 18 °C in May, June and September, October (6.1–16.4 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	25.4	9.7	30	6	14:18
June	32.8	16.4	13	3	14:54
July	35.1	19.8	15	2	14:40
August	33.3	18.3	24	5	13:44
September	28.9	13.8	28	5	12:29
October	19.6	6.1	54	7	11:14

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Grand Junction, Pueblo is 3 days earlier and Cheyenne 33 days later.

City	Distance	Date	Difference
Denver	316 km	28 May – 6 July	22 days later
Colorado Springs	326 km	6 June – 6 July	31 days later
Salt Lake City	339 km	19 May – 17 July	13 days later
Fort Collins	340 km	7 June – 12 July	32 days later
Pueblo	356 km	3 May – 19 July	3 days earlier
Cheyenne	392 km	8 June – 4 July	33 days later

Where to buy watermelon plants and seeds near Grand Junction

Buy plants ready to set out from 6 May to 18 July (from 15 April to 18 July for an unheated greenhouse); seed for raising your own is sown from 18 March to 20 June. Within 15 km of Grand Junction OpenStreetMap lists 5 garden centres, 1 farm-supply shop, 1 market and 1 farm shop (collected 28 October 2026).

Upland Gravel LLC — garden centre
28 1/2 Road 454, 81501 Grand Junction · Mon closed; Tue–Fri 07:00–17:00; Sat 09:00–15:00; Sun closed · 5 km · uplandgravel.com
Meadowlark Garden — garden centre
Broadway 2259, 81507 Grand Junction · Tue–Sun 08:30–17:30 · 6 km · meadowlarkgardencenter.com
Mount Garfield Greenhouse & Nursery — garden centre
F Road 3162, 81504 Grand Junction · Mar, Jul–Oct Mon–Sat 09:00–17:30; Mar, Jul–Oct Sun 10:00–16:00; Apr–May Mon–Sat 08:00–18:00; Apr–May Sun 10:00–17:00; Jun Mon–Sat 09:00–18:00; Jun Sun 10:00–16:00; Jul 04 closed · 9 km · mtgarfieldgreenhouse.com
Mesa Mycology Center — garden centre
North Avenue 2863, 81501 Grand Junction · Mon–Fri 10:00–18:00; Sat 12:00–16:00; Sun closed · 4 km

Each window starts on the Greenly calendar date and ends on the last day that still leaves the crop’s days to harvest (from its card) before the average first autumn frost, plus six weeks of picking for crops harvested over weeks (tomatoes, peppers, aubergines, cucumbers, courgettes, pumpkins, watermelons, beans) — our rule; earlier in the window is safer.

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