Planting calendar for Denver, Colorado

Dates from 30 years of records at the Denver Water Dept weather station, 1.4 miles from Denver, worked out crop by crop with the same method as the Year Round Garden app.

Denver at a glance

Weather station: Denver Water Dept · 1.4 mi
USDA zone: 6a
Last spring frost: typically Apr 30; 1 year in 10 after May 13
First fall frost: typically Oct 12; 1 year in 10 before Sep 28
Frost-free season: about 165 days
Hottest month: July: highs 91°F, nights 62°F
Coldest month: December: highs 47°F, nights 21°F
Rain: 16 in. a year, most in April, May and July

What shapes the seasons here

The last spring frost in Denver typically comes around Apr 30, but 1 year in 10 it comes after May 13. The first fall frost typically arrives around Oct 12. That leaves about 165 frost-free days for tender crops like tomatoes, peppers and squash.

Denver gets about 16 inches of rain a year, most of it in April, May and July.

140 of the 174 crops in the app grow here; 34 need a different climate (listed near the bottom).

When to plant the most popular crops

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Tomato (slicing)

Tomato (cherry & grape)

Pepper (sweet / bell)

Pepper (hot / chili)

Eggplant

Cucumber (slicing)

Summer squash & zucchini

Watermelon

Bean (bush snap)

Sweet corn

Okra

Potato

Pea (snap & snow)

Lettuce (leaf & mesclun)

Spinach

Kale

Collard greens

Broccoli

Cabbage

Carrot

Radish

Onion (bulbing)

Garlic

Basil

Cilantro

Strawberry

Best Can plant Start indoors

Get these dates as reminders for your exact yard

The free Year Round Garden app uses the weather station nearest your own address, not just the city. It reminds you when to start seeds, plant and harvest, sends frost and storm alerts from the National Weather Service, and keeps a garden journal. No account needed, in English and Spanish.

Download on the App Store Free for up to 5 plants on iPhone and Android.

What to plant in Denver, month by month

January0

Too cold to plant outdoors. Plan beds, order seeds and start the ones listed indoors.

Start seeds indoors

Onion (bulbing), Pansy / viola

February0

Too cold to plant outdoors. Plan beds, order seeds and start the ones listed indoors.

Start seeds indoors

Artichoke, Broccoli, Cabbage, Celeriac (celery root), Celery, Leek, Parsley, Stock

March11

Best time to plant

Vegetables: Arugula, Kale, Mustard greens, Onion (bulbing), Pea (shelling / English), Pea (snap & snow), Shallot, Spinach

Flowers: Larkspur, Pansy / viola, Sweet pea (flower)

Start seeds indoors

Cardoon, Cauliflower, Celeriac (celery root), Celery, Onion (bulbing), Pepper (hot / chili), Pepper (sweet / bell), Tomato (early / short-season), Catnip, Lavender, Lemon balm, Lovage, Rosemary, Purple coneflower (echinacea), Statice, Strawflower

April52

Best time to plant

Vegetables: Artichoke, Arugula, Asparagus, Beet, Broccoli, Broccoli raab (rapini), Cabbage, Carrot, Cauliflower, Celeriac (celery root), Chickpea / garbanzo, Chinese broccoli (gai lan), Collard greens, Daikon radish, Garden cress, Green onion / scallion, Kale, Kohlrabi, Leek, Lettuce (leaf & mesclun), Mache (corn salad), Mustard greens, Onion (bulbing), Radicchio, Radish, Rhubarb, Salsify, Spinach, Swiss chard, Turnip, Watercress

Herbs: Borage, Caraway, Catnip, Chamomile, Chervil, Dill, Lemon balm, Lovage, Mint, Parsley, Sorrel (French / garden)

Fruit: Blackberry, Grape (bunch), Raspberry, Strawberry

Flowers: Bachelor's button (cornflower), Calendula, California poppy, Pansy / viola, Stock, Sweet alyssum

Can also plant

Pea (shelling / English), Pea (snap & snow), Potato, Shallot, Sunchoke (Jerusalem artichoke), Coreopsis (tickseed)

Start seeds indoors

Brussels sprouts, Eggplant, Leek, Onion (bulbing), Pepper (hot / chili), Pepper (sweet / bell), Tomatillo, Tomato (cherry & grape), Tomato (heat-set varieties), Tomato (paste / determinate), Tomato (slicing), Anise hyssop, Bee balm (bergamot), Chives, Feverfew, Garlic chives, Lavender, Lovage, Marjoram, Oregano, Rosemary, Sage, Shiso (perilla), Thyme, Winter savory, Cucamelon / mouse melon, Ground cherry, Annual salvia, Milkweed (native), Purple coneflower (echinacea)

May37

Best time to plant

Vegetables: Armenian cucumber, Bean (bush snap), Bean (dry / shelling), Bean (pole), Bitter melon, Cardoon, Celery, Cucumber (pickling), Cucumber (slicing), New Zealand spinach, Parsnip, Pepper (sweet / bell), Popcorn, Pumpkin, Salsify, Summer squash & zucchini, Sunchoke (Jerusalem artichoke), Sweet corn, Tomatillo, Tomato (cherry & grape), Tomato (early / short-season), Tomato (paste / determinate), Tomato (slicing), Winter squash

Herbs: Borage, Catnip, Epazote, Lemon balm, Lovage, Mint, Shiso (perilla), Sorrel (French / garden), Summer savory

Fruit: Cucamelon / mouse melon, Ground cherry

Flowers: Statice, Strawflower

Can also plant

Asparagus, Beet, Celeriac (celery root), Chickpea / garbanzo, Chinese broccoli (gai lan), Collard greens, Garden cress, Green onion / scallion, Kale, Kohlrabi, Leek, Onion (bulbing), Potato, Radish, Shallot, Swiss chard, Turnip, Watercress, Anise hyssop, Bee balm (bergamot), Chamomile, Chives, Dill, Fenugreek (methi), Feverfew, Garlic chives, Lavender, Lemon verbena, Marjoram, Oregano, Parsley, Rosemary, Sage, Tarragon (French), Thyme, Vietnamese coriander (rau ram), Winter savory, Blackberry, Grape (bunch), Strawberry, Annual salvia, Black-eyed Susan, Calendula, Cleome (spider flower), Coreopsis (tickseed), Marigold, Milkweed (native), Nasturtium, Purple coneflower (echinacea), Sunflower, Sweet alyssum

Start seeds indoors

Brussels sprouts, Cabbage, Malabar spinach, Tomato (cherry & grape), Tomato (early / short-season), Tomato (heat-set varieties), Tomato (paste / determinate), Tomato (slicing), Anise hyssop, Basil, Bee balm (bergamot), Chives, Garlic chives, Marjoram, Oregano, Parsley, Winter savory, Annual salvia, Globe amaranth (gomphrena), Marigold, Milkweed (native), Pentas (Egyptian star cluster), Statice, Strawflower

June54

Best time to plant

Vegetables: Amaranth greens / callaloo, Armenian cucumber, Bean (dry / shelling), Bean (lima), Bitter melon, Brussels sprouts, Celeriac (celery root), Celery, Edamame, Eggplant, Leek, Onion (bulbing), Pepper (hot / chili), Pepper (sweet / bell), Potato, Purslane, Shallot, Sweet corn, Tomato (heat-set varieties), Tomato (paste / determinate), Tomato (slicing), Winter squash

Herbs: Anise hyssop, Basil, Bee balm (bergamot), Chives, Cuban oregano, Feverfew, Garlic chives, Lavender, Lemon verbena, Marjoram, Oregano, Papalo, Rosemary, Sage, Stevia, Tarragon (French), Thyme, Vietnamese coriander (rau ram), Winter savory

Fruit: Cantaloupe & melons, Watermelon

Flowers: Annual salvia, Black-eyed Susan, Cleome (spider flower), Coreopsis (tickseed), Cosmos, Globe amaranth (gomphrena), Marigold, Milkweed (native), Purple coneflower (echinacea), Sunflower, Zinnia

Can also plant

Bean (bush snap), Bean (pole), Cabbage, Carrot, Chickpea / garbanzo, Chinese broccoli (gai lan), Collard greens, Cucumber (pickling), Cucumber (slicing), New Zealand spinach, Parsnip, Popcorn, Summer squash & zucchini, Swiss chard, Tomatillo, Tomato (cherry & grape), Tomato (early / short-season), Borage, Caraway, Chamomile, Epazote, Parsley, Shiso (perilla), Summer savory, Cucamelon / mouse melon, Ground cherry, Statice, Strawflower

Start seeds indoors

Broccoli, Cabbage, Cauliflower, Lettuce (romaine & head), Basil, Pansy / viola, Stock, Strawflower

July48

Best time to plant

Vegetables: Amaranth greens / callaloo, Armenian cucumber, Bean (bush snap), Bean (pole), Beet, Bitter melon, Broccoli, Brussels sprouts, Cabbage, Carrot, Cauliflower, Chinese broccoli (gai lan), Cucumber (pickling), Cucumber (slicing), Leek, Lettuce (romaine & head), Napa / Chinese cabbage, New Zealand spinach, Okinawa spinach, Okra, Pea (shelling / English), Pea (snap & snow), Purslane, Shallot, Summer squash & zucchini, Tomato (cherry & grape), Tomato (early / short-season), Tomato (heat-set varieties), Tomato (paste / determinate)

Herbs: Basil, Borage, Caraway, Chamomile, Cilantro, Cuban oregano, Dill, Epazote, Parsley, Vietnamese coriander (rau ram)

Flowers: Annual salvia, Calendula, Coreopsis (tickseed), Marigold, Nasturtium, Pentas (Egyptian star cluster), Statice, Strawflower, Zinnia

Can also plant

Arugula, Broccoli raab (rapini), Collard greens, Kale, Kohlrabi, Komatsuna (mustard spinach), Lettuce (leaf & mesclun), Swiss chard, Turnip, Fenugreek (methi), Shiso (perilla), Summer savory, Ground cherry, Bachelor's button (cornflower), California poppy, Cosmos, Globe amaranth (gomphrena), Sweet alyssum

August27

Best time to plant

Vegetables: Amaranth greens / callaloo, Arugula, Beet, Broccoli raab (rapini), Chinese broccoli (gai lan), Collard greens, Garden cress, Kale, Kohlrabi, Komatsuna (mustard spinach), Lettuce (leaf & mesclun), Lettuce (romaine & head), Mache (corn salad), Mustard greens, Pea (shelling / English), Pea (snap & snow), Swiss chard, Turnip

Herbs: Chamomile, Chervil, Cilantro, Dill, Fenugreek (methi)

Flowers: Calendula, Pansy / viola, Stock, Sweet alyssum

Can also plant

Radish, Spinach

September4

Best time to plant

Vegetables: Elephant garlic, Garden cress, Garlic, Radish

Can also plant

Spinach

October2

Best time to plant

Vegetables: Elephant garlic, Garlic

November0

Too cold to plant outdoors. A good month to plan beds and order seeds.

December0

Too cold to plant outdoors. A good month to plan beds and order seeds.

Every crop that grows in Denver

140 of 174 crops in the app fit this climate. Dates are for planting outdoors; “Start indoors” is for seeds you grow into transplants.

Vegetables

Crop	Best time to plant	Also possible	Start indoors	How
Amaranth greens / callaloo	Jun 5–19, Jul 25–Aug 10	Jun 20–Jul 24	—	Sow seeds
Armenian cucumber	May 19–Jun 2, Jun 23–Jul 13	Jun 3–22	—	Sow seeds
Artichoke	Apr 16–25	—	Feb 12–21	Set out plants
Arugula	Mar 25–Apr 21, Aug 15–Sep 4	Mar 19–24, Apr 22–May 7, Jul 19–Aug 14	—	Sow seeds
Asparagus	Apr 2–24	Apr 25–May 28	—	Set out plants
Bean (bush snap)	May 19–Jun 2, Jul 7–28	Jun 3–Jul 6	—	Sow seeds
Bean (dry / shelling)	May 19–Jun 23	—	—	Sow seeds
Bean (lima)	Jun 5–28	—	—	Sow seeds
Bean (pole)	May 19–Jun 2, Jun 27–Jul 18	Jun 3–26	—	Sow seeds
Beet	Apr 2–23, Jul 23–Aug 13	Apr 24–May 14, Jun 23–Jul 22	—	Sow seeds
Bitter melon	May 19–Jun 2, Jun 25–Jul 16	Jun 3–24	—	Sow seeds
Broccoli	Apr 2–16, Jul 16–Aug 5	Apr 17–26	Feb 19–Mar 5, Jun 4–24	Set out plants
Broccoli raab (rapini)	Apr 2–16, Aug 10–23	Apr 17–22, Jul 19–Aug 9	—	Sow seeds
Brussels sprouts	Jun 2–16, Jun 27–Jul 7	Jun 17–26	Apr 21–May 5, May 16–26	Set out plants
Cabbage	Mar 26–Apr 9, Jul 3–24	Apr 10–27, Jun 17–Jul 2	Feb 12–26, May 22–Jun 12	Set out plants
Cardoon	Apr 30–May 14	May 15–30	Feb 26–Mar 12	Set out plants
Carrot	Apr 9–30, Jul 13–Aug 3	May 1–8, Jun 15–Jul 12	—	Sow seeds
Cauliflower	Apr 9–23, Jul 16–22	Apr 24–30	Feb 26–Mar 12, Jun 4–10	Set out plants
Celeriac (celery root)	Apr 18–May 2, May 29–Jun 19	May 3–28	Jan 31–Feb 14, Mar 13–Apr 3	Set out plants
Celery	May 4–18, May 25–Jun 15	—	Feb 16–Mar 2, Mar 9–30	Set out plants
Chickpea / garbanzo	Apr 18–May 2	May 3–Jun 12	—	Sow seeds
Chinese broccoli (gai lan)	Apr 9–30, Jul 21–Aug 10	May 1–22, Jun 8–Jul 20	—	Sow seeds
Collard greens	Apr 2–16, Jul 27–Aug 17	Apr 17–Jul 26	—	Sow seeds
Cucumber (pickling)	May 19–Jun 2, Jun 30–Jul 21	Jun 3–29	—	Sow seeds
Cucumber (slicing)	May 19–Jun 2, Jun 28–Jul 18	Jun 3–27	—	Sow seeds
Daikon radish	Apr 9–23	—	—	Sow seeds
Edamame	Jun 5–30	—	—	Sow seeds
Eggplant	Jun 5–Jul 3	—	Apr 3–May 1	Set out plants
Elephant garlic	Sep 21–Oct 26	—	—	Sow seeds
Garden cress	Apr 16–May 6, Aug 25–Sep 8	May 7–22, Aug 5–24	—	Sow seeds
Garlic	Sep 21–Oct 26	—	—	Sow seeds
Green onion / scallion	Apr 2–16	Apr 17–May 28	—	Sow seeds
Kale	Mar 19–Apr 9, Aug 9–29	Apr 10–May 15, Jun 22–Aug 8	—	Sow seeds
Kohlrabi	Apr 2–16, Jul 31–Aug 20	Apr 17–May 17, Jul 10–30	—	Sow seeds
Komatsuna (mustard spinach)	Jul 27–Aug 28	Jun 25–Jul 26	—	Sow seeds
Leek	Apr 2–15, Jun 17–Jul 8	May 2–Jun 16	Jan 29–Feb 11, Apr 15–May 6	Set out plants
Lettuce (leaf & mesclun)	Apr 2–19, Aug 6–25	Apr 20–30, Jul 11–Aug 5	—	Sow seeds
Lettuce (romaine & head)	Jul 16–Aug 8	—	Jun 11–Jul 4	Set out plants
Mache (corn salad)	Apr 2–8, Aug 24–Sep 6	—	—	Sow seeds
Malabar spinach	Jun 28–Jul 4	—	May 10–16	Set out plants
Mustard greens	Mar 21–Apr 15, Aug 19–Sep 2	Mar 19–20, Apr 16–28, Jul 25–Aug 18	—	Sow seeds
Napa / Chinese cabbage	Jul 17–Aug 3	Jun 26–Jul 16	—	Sow seeds
New Zealand spinach	May 19–Jun 2, Jun 30–Jul 20	Jun 3–29	—	Sow seeds
Okinawa spinach	Jun 28–Jul 12	—	—	Set out plants
Okra	Jun 28–Jul 10	—	—	Sow seeds
Onion (bulbing)	Mar 19–Apr 9, May 31–Jun 29	Apr 10–May 30	Mar 15–Apr 13, Jan 1–22	Set out plants
Parsnip	Apr 27–May 18	May 19–Jul 3	—	Sow seeds
Pea (shelling / English)	Mar 19–Apr 2, Jul 21–Aug 10	Apr 3–30, Jul 16–20	—	Sow seeds
Pea (snap & snow)	Mar 19–Apr 2, Jul 21–Aug 10	Apr 3–29, Jul 16–20	—	Sow seeds
Pepper (hot / chili)	May 26–Jun 26	—	Mar 24–Apr 24	Set out plants
Pepper (sweet / bell)	May 19–Jun 2, Jun 15–Jul 6	Jun 3–14	Mar 17–31, Apr 13–May 4	Set out plants
Popcorn	May 19–26	May 27–Jun 10	—	Sow seeds
Potato	May 27–Jun 25	Apr 2–May 26	—	Sow seeds
Pumpkin	May 19–Jun 1	—	—	Sow seeds
Purslane	Jun 5–19, Jul 6–27	Jun 20–Jul 5	—	Sow seeds
Radicchio	Apr 2–9	—	—	Sow seeds
Radish	Apr 1–30, Aug 27–Sep 16	Mar 26–31, May 1–19, Aug 2–26	—	Sow seeds
Rhubarb	Apr 2–25	—	—	Set out plants
Salsify	Apr 9–30, May 9–30	May 1–8	—	Sow seeds
Shallot	Mar 19–Apr 2, Jun 22–Jul 13	Apr 3–Jun 21	—	Sow seeds
Spinach	Mar 19–Apr 12	Apr 13–19, Aug 8–Sep 11	—	Sow seeds
Summer squash & zucchini	May 19–Jun 2, Jul 3–23	Jun 3–Jul 2	—	Sow seeds
Sunchoke (Jerusalem artichoke)	Apr 30–May 21	Apr 9–29	—	Sow seeds
Sweet corn	May 19–26, Jun 15–Jul 5	May 27–Jun 14	—	Sow seeds
Swiss chard	Apr 9–30, Jul 28–Aug 18	May 1–Jul 27	—	Sow seeds
Tomatillo	May 19–Jun 2	Jun 3–Jul 3	Apr 7–21	Set out plants
Tomato (cherry & grape)	May 19–Jun 2, Jun 30–Jul 20	Jun 3–29	Mar 31–Apr 14, May 12–Jun 1	Set out plants
Tomato (early / short-season)	May 7–14, Jul 5–25	May 15–Jul 4	Mar 19–26, May 17–Jun 6	Set out plants
Tomato (heat-set varieties)	Jun 5–Jul 8	—	Apr 17–May 20	Set out plants
Tomato (paste / determinate)	May 19–Jun 2, Jun 17–Jul 8	Jun 3–16	Mar 31–Apr 14, Apr 29–May 20	Set out plants
Tomato (slicing)	May 19–Jun 2, Jun 15–Jul 5	Jun 3–14	Mar 31–Apr 14, Apr 27–May 17	Set out plants
Turnip	Apr 2–16, Aug 2–23	Apr 17–May 17, Jul 10–Aug 1	—	Sow seeds
Watercress	Apr 9–23	Apr 24–May 25	—	Sow seeds
Winter squash	May 19–Jun 11	—	—	Sow seeds

Herbs

Crop	Best time to plant	Also possible	Start indoors	How
Anise hyssop	May 31–Jun 25	Apr 30–May 30	Apr 16–May 11	Set out plants
Basil	Jun 5–12, Jun 28–Jul 18	Jun 13–27	May 1–8, May 24–Jun 13	Set out plants
Bee balm (bergamot)	May 31–Jun 25	Apr 30–May 30	Apr 12–May 7	Set out plants
Borage	Apr 23–May 9, Jul 1–Aug 4	May 10–Jun 30	—	Sow seeds
Caraway	Apr 9–23, Jul 3–24	Apr 24–30, Jun 1–Jul 2	—	Sow seeds
Catnip	Apr 16–May 7	May 8–28	Feb 26–Mar 19	Set out plants
Chamomile	Apr 2–16, Jul 18–Aug 8	Apr 17–May 10, Jun 15–Jul 17	—	Sow seeds
Chervil	Apr 9–15, Aug 8–23	—	—	Sow seeds
Chives	May 29–Jun 25	Apr 30–May 28	Apr 10–May 7	Set out plants
Cilantro	Jul 16–Aug 15	—	—	Sow seeds
Cuban oregano	Jun 23–Jul 17	Jun 5–22, Jul 18–23	—	Set out plants
Dill	Apr 16–23, Jul 19–Aug 9	Apr 24–May 21, Jul 2–18	—	Sow seeds
Epazote	May 19–Jun 2, Jul 12–Aug 2	Jun 3–Jul 11	—	Sow seeds
Fenugreek (methi)	Jul 29–Aug 21	Apr 30–May 10, Jul 14–28	—	Sow seeds
Feverfew	May 31–Jun 18	Apr 23–May 30	Apr 12–30	Set out plants
Garlic chives	May 29–Jun 25	Apr 30–May 28	Apr 10–May 7	Set out plants
Lavender	Jun 1–25	May 7–31	Mar 16–Apr 9	Set out plants
Lemon balm	Apr 16–May 7	May 8–28	Mar 12–Apr 2	Set out plants
Lemon verbena	Jun 1–25	May 7–31	—	Set out plants
Lovage	Apr 16–May 28	—	Feb 26–Apr 9	Set out plants
Marjoram	Jun 1–25	May 7–31	Apr 13–May 7	Set out plants
Mint	Apr 16–May 7	May 8–28	—	Set out plants
Oregano	May 28–Jun 25	Apr 30–May 27	Apr 9–May 7	Set out plants
Papalo	Jun 5–19	Jun 20–Jul 8	—	Sow seeds
Parsley	Apr 9–23, Jul 3–24	Apr 24–Jul 2	Feb 5–19, May 1–22	Set out plants
Rosemary	Jun 1–25	May 7–31	Mar 16–Apr 9	Set out plants
Sage	May 29–Jun 18	Apr 23–May 28	Apr 10–30	Set out plants
Shiso (perilla)	May 19–26	May 27–Jul 15	Apr 14–21	Set out plants
Sorrel (French / garden)	Apr 9–May 7	May 8–Jun 4	—	Sow seeds
Stevia	Jun 5–23	—	—	Set out plants
Summer savory	May 4–18	May 19–Jul 18	—	Sow seeds
Tarragon (French)	Jun 4–25	Apr 30–Jun 3	—	Set out plants
Thyme	May 28–Jun 25	Apr 30–May 27	Apr 2–30	Set out plants
Vietnamese coriander (rau ram)	Jun 16–Jul 14	May 19–Jun 15	—	Set out plants
Winter savory	Jun 4–25	Apr 30–Jun 3	Apr 16–May 7	Set out plants

Fruit

Crop	Best time to plant	Also possible	Start indoors	How
Blackberry	Mar 26–Apr 16	Apr 17–May 28	—	Set out plants
Cantaloupe & melons	Jun 5–23	—	—	Sow seeds
Cucamelon / mouse melon	May 19–Jun 2	Jun 3–Jul 8	Apr 14–28	Set out plants
Grape (bunch)	Apr 2–30	May 1–14	—	Set out plants
Ground cherry	May 19–Jun 2	Jun 3–Jul 13	Mar 31–Apr 14	Set out plants
Raspberry	Apr 2–16	Apr 17–26	—	Set out plants
Strawberry	Apr 2–30	May 1–28	—	Set out plants
Watermelon	Jun 5–21	—	—	Sow seeds

Flowers

Crop	Best time to plant	Also possible	Start indoors	How
Annual salvia	Jun 16–Jul 23	May 19–Jun 15, Jul 24–Aug 2	Apr 7–May 14	Set out plants
Bachelor's button (cornflower)	Apr 2–16	Apr 17–23, Jun 30–Jul 7, Jul 16–Aug 5	—	Sow seeds
Black-eyed Susan	Jun 2–Jul 5	Apr 30–Jun 1	—	Sow seeds
Calendula	Apr 16–May 1, Jul 23–Aug 20	May 2–17, Jun 25–Jul 22	—	Sow seeds
California poppy	Apr 2–16	Apr 17–23, Jun 30–Jul 7, Jul 16–Aug 5	—	Sow seeds
Cleome (spider flower)	Jun 11–Jul 3	May 19–Jun 10	—	Sow seeds
Coreopsis (tickseed)	Jun 4–Jul 14	Apr 2–Jun 3	—	Sow seeds
Cosmos	Jun 17–Jul 6	Jun 5–16, Jul 7–13	—	Sow seeds
Globe amaranth (gomphrena)	Jun 17–Jul 6	Jun 5–16, Jul 7–13	Apr 29–May 18	Set out plants
Larkspur	Mar 19–30	—	—	Sow seeds
Marigold	Jun 15–Jul 20	May 19–Jun 14, Jul 21–28	Apr 27–Jun 1	Set out plants
Milkweed (native)	May 28–Jun 25	Apr 30–May 27	Apr 23–May 21	Set out plants
Nasturtium	Jul 8–Aug 2	May 4–19, Jun 27–Jul 7	—	Sow seeds
Pansy / viola	Mar 19–Apr 9, Aug 17–Sep 4	Apr 10–May 1	Jun 1–19, Jan 1–22	Set out plants
Pentas (Egyptian star cluster)	Jun 28–Jul 26	—	Apr 26–May 24	Set out plants
Purple coneflower (echinacea)	Jun 4–25	Apr 30–Jun 3	Mar 19–Apr 9	Set out plants
Statice	Apr 30–May 14, Jul 4–25	May 15–Jul 3	Feb 26–Mar 12, May 2–23	Set out plants
Stock	Apr 16–30, Aug 8–23	—	Feb 12–26, Jun 6–21	Set out plants
Strawflower	May 4–18, Jul 12–Aug 1	May 19–Jul 11	Mar 16–30, May 24–Jun 13	Set out plants
Sunflower	Jun 8–28	May 19–Jun 7	—	Sow seeds
Sweet alyssum	Apr 9–May 2, Jul 29–Aug 22	May 3–19, Jun 27–Jul 28	—	Sow seeds
Sweet pea (flower)	Mar 19–Apr 6	—	—	Sow seeds
Zinnia	Jun 18–Jul 8	Jun 5–17, Jul 9–15	—	Sow seeds

Crops that struggle in Denver

These need a climate Denver doesn't have. Pots, shade cloth or a greenhouse can stretch the rules.

Banana: Has to live outdoors through winter and needs nights no colder than about 45°F; the coldest month here averages 21°F.
Bay laurel: Has to live outdoors through winter and needs nights no colder than about 32°F; the coldest month here averages 21°F.
Blueberry: It needs acid soil, and dry-climate soil is usually alkaline. Grow it in a large pot of acid potting mix.
Bok choy / pak choi: The frost-free season (about 165 days) is shorter than the 52 days it needs.
Bottle gourd / cucuzza: The frost-free season (about 165 days) is shorter than the 70 days it needs.
Cassava (yuca): Has to live outdoors through winter and needs nights no colder than about 40°F; the coldest month here averages 21°F.
Celosia: The frost-free season (about 165 days) is shorter than the 80 days it needs.
Chaya (tree spinach): Has to live outdoors through winter and needs nights no colder than about 40°F; the coldest month here averages 21°F.
Culantro: The frost-free season (about 165 days) is shorter than the 70 days it needs.
Endive & escarole: The frost-free season (about 165 days) is shorter than the 85 days it needs.
Fava bean: The frost-free season (about 165 days) is shorter than the 90 days it needs.
Fennel (bulb): The frost-free season (about 165 days) is shorter than the 75 days it needs.
Fig: Has to live outdoors through winter and needs nights no colder than about 22°F; the coldest month here averages 21°F.
Ginger: The frost-free season (about 165 days) is shorter than the 270 days it needs.
Jicama: The frost-free season (about 165 days) is shorter than the 180 days it needs.
Lemongrass: The frost-free season (about 165 days) is shorter than the 88 days it needs.
Luffa gourd: The frost-free season (about 165 days) is shorter than the 105 days it needs.
Moringa: The frost-free season (about 165 days) is shorter than the 75 days it needs.
Muscadine grape: Has to live outdoors through winter and needs nights no colder than about 26°F; the coldest month here averages 21°F.
Papaya: Has to live outdoors through winter and needs nights no colder than about 48°F; the coldest month here averages 21°F.
Passion fruit: Has to live outdoors through winter and needs nights no colder than about 44°F; the coldest month here averages 21°F.
Peanut: The frost-free season (about 165 days) is shorter than the 130 days it needs.
Pigeon pea: The frost-free season (about 165 days) is shorter than the 150 days it needs.
Pineapple: Has to live outdoors through winter and needs nights no colder than about 45°F; the coldest month here averages 21°F.
Roselle: The frost-free season (about 165 days) is shorter than the 165 days it needs.
Rutabaga: The frost-free season (about 165 days) is shorter than the 95 days it needs.
Seminole pumpkin / calabaza: The frost-free season (about 165 days) is shorter than the 108 days it needs.
Snapdragon: The frost-free season (about 165 days) is shorter than the 90 days it needs.
Southern pea / cowpea: The frost-free season (about 165 days) is shorter than the 75 days it needs.
Sweet potato: The frost-free season (about 165 days) is shorter than the 105 days it needs.
Taro (dasheen): The frost-free season (about 165 days) is shorter than the 225 days it needs.
Winged bean: The frost-free season (about 165 days) is shorter than the 105 days it needs.
Winter melon / wax gourd: The frost-free season (about 165 days) is shorter than the 105 days it needs.
Yardlong bean: The frost-free season (about 165 days) is shorter than the 70 days it needs.

Nearby planting calendars

Cheyenne, WY 97 mi · last frost around May 14
Albuquerque, NM 334 mi · last frost around Apr 6
Salt Lake City, UT 371 mi · last frost around Mar 31
Wichita, KS 436 mi · last frost around Apr 11
Billings, MT 454 mi · last frost around May 10
All Colorado cities

How these dates are worked out

Each crop has temperature limits and timing from university extension guides: how cold a night it can take, how much heat it can stand, how long it takes to mature, and how far before or after the last frost it goes in. Those are checked day by day against the Denver Water Dept station's NOAA 1991–2020 climate normals (average highs, lows, rain and frost dates). Dates are estimates for a typical year; a sheltered yard, a slope or a cold pocket can shift them by a week or two.

Weather: NOAA National Centers for Environmental Information, 1991–2020 U.S. Climate Normals. Crop timing: university extension guides (sources listed for each crop in the app). City locations: GeoNames (CC BY 4.0).