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The best time to plant herbs in Denver is after the last frost in spring, typically between mid-May and early June.
But planting herbs in Denver isn’t a simple one-size-fits-all answer because our unique high-altitude climate, dramatic temperature swings, and semi-arid conditions change the rules compared to other regions.
When you plant herbs in Denver depends heavily on whether you’re growing cold-hardy perennials like mint and chives, or warm-season annuals like basil and cilantro.
You also have to factor in our famously unpredictable late snowstorms, which can sneak up on you even in late May.
So, if you’ve been wondering when to plant herbs in Denver, this guide will break down the exact timing for each type of herb, plus the best practices to keep them thriving in our Mile High City.
Let’s dig into the details so your herb garden gets off to a strong start.
When to Plant Herbs in Denver: The Ultimate Timing Guide
When to plant herbs in Denver really comes down to understanding our two distinct growing windows.
We have a short, intense spring that warms up quickly, followed by a long, mild fall that’s perfect for a second planting round.
Let’s look at the key factors that determine the best planting herbs in Denver schedule for your garden.
1. Know Your Last Frost Date
Your absolute starting point for planting herbs in Denver is our average last frost date.
For most of the Denver metro area, that falls around May 5th to May 15th.
But I’m not going to sugarcoat it: we’ve seen snow as late as June in some foothill neighborhoods.
So, while mid-May is a good rule of thumb, always watch the 10-day forecast before you commit to planting herbs in Denver.
If a cold snap is coming, hold off on tender herbs and cover your hardy ones with a frost cloth overnight.
2. Cold-Hardy Herbs Can Go In Early
When to plant herbs in Denver for cool-season varieties is actually much earlier than you might think.
Herbs like chives, thyme, oregano, sage, and mint are tough as nails and can handle light frosts.
You can plant these in early April, or even late March if the ground has thawed and isn’t waterlogged.
These perennials will survive a few chilly nights, and they’ll reward you with early growth that kicks off as soon as the soil warms.
For these, planting herbs in Denver in early spring gives them a long season to establish deep roots before summer heat arrives.
3. Warm-Season Herbs Need Patience
The tricky part about deciding when to plant herbs in Denver is for the sun-loving annuals.
Basil, cilantro, dill, and parsley are warm-season herbs that absolutely hate cold soil and frost.
If you plant these too early, they’ll either rot in the ground or get zapped by an overnight freeze.
The safest window for planting herbs in Denver of this type is after May 15th, once soil temperatures reach at least 60°F.
I’ve learned the hard way that a beautiful 70°F day in early May can be followed by a 28°F night that wipes out your basil entirely.
So, patience is your best friend when you’re figuring out when to plant herbs in Denver for these delicate varieties.
4. Fall Planting for a Second Harvest
Here’s a secret that many Denver gardeners miss: when to plant herbs in Denver isn’t just a spring question.
Our cool fall weather is ideal for a second round of planting herbs in Denver, especially for cilantro, dill, and arugula.
You can sow these directly in the ground in late August or early September.
The shorter days and cooler nights will actually make these herbs sweeter and less likely to bolt (go to seed).
This fall window is one of the best times to plant herbs in Denver because you get a fresh harvest well into October.
Just keep in mind that your first hard frost usually arrives around mid-October, so you have a solid 6-8 week window.
Denver-Specific Challenges for Planting Herbs
Even if you nail the timing for planting herbs in Denver, our unique environment will throw some curveballs at you.
Here’s what you need to watch out for when you’re planting herbs in Denver.
1. Intense UV Radiation
Denver sits at 5,280 feet, which means we get about 25% more UV radiation than at sea level.
This intense sun can scorch tender herb leaves, especially young transplants.
When you’re planting herbs in Denver, consider giving them partial shade for the first week or two.
You can use a shade cloth or just plant them on the east side of a taller plant.
Once they’re established, most herbs will handle the sun fine, but that initial shock is real.
2. Dry Air and Rapid Evaporation
Our semi-arid climate means the air sucks moisture out of everything.
If you’re planting herbs in Denver, you absolutely must mulch the soil to retain water.
A 2-inch layer of straw, wood chips, or even grass clippings will protect the roots and keep the soil from drying out in a single afternoon.
Also, be prepared to water more frequently than you would in a humid climate.
Check the top inch of soil daily during hot spells.
Herbs like rosemary and thyme prefer drier soil, but they still need a consistent drink during our hot, dry summers.
3. Unpredictable Temperature Swings
A 40-degree swing between day and night is common in Denver.
This fluctuation stresses plants, so when you’re timing when to plant herbs in Denver, choose varieties that are known for resilience.
Oregano, tarragon, and sage are absolute champs in this climate.
They shrug off the cold nights and still produce well in the hot days.
Avoid tender herbs like lemongrass or stevia, as they simply can’t handle these swings.
Best Herbs to Grow in Denver and When to Plant Them
Let’s get specific about which herbs to plant and the exact calendar for planting herbs in Denver.
This list covers the most reliable performers for our region.
Early Spring (April) Plantings
Chives can go in the ground in early April, and they’ll come back year after year.
Thyme and oregano are also great early choices, and they’re extremely drought-tolerant once established.
Sage is another perennial that thrives with early spring planting herbs in Denver.
Mint should be planted in a container though, because it will take over your entire garden if you give it ground space.
These hardy herbs don’t mind cooler soil, and they’ll handle a surprise snow shower without complaint.
Late Spring (Late May to Early June) Plantings
Basil should be your last herb to go in the ground, as it’s the most frost-sensitive.
Cilantro can be planted in late May, but it will bolt quickly in our June heat, so stagger your sowing every two weeks.
Dill is another warm-season herb that’s best planted after the soil warms.
Parsley is a biennial that can actually handle a light frost, so you can push it to mid-May.
When you’re planting herbs in Denver during this window, water them in well and apply a light layer of compost.
Fall (Late August) Plantings
For a fall crop, you can plant cilantro, dill, and parsley again.
These cool-season herbs will actually taste better in the fall than they did in the heat of early summer.
You can also plant garlic chives and sorrel in early September for a late-season harvest.
This fall planting herbs in Denver schedule works because the soil is still warm from summer, which encourages fast germination.
Once the seedlings are up, the cooler temps keep them tender and slow to bolt.
So, When Is the Best Time to Plant Herbs in Denver?
The best time to plant herbs in Denver is a two-part answer because it depends on the herb type.
For cold-hardy perennials, you should plant herbs in Denver in early April.
For warm-season annuals, you should wait until after mid-May, ideally late May or early June.
And for a bonus round, you can plant herbs in Denver again in late August for a fantastic fall harvest.
The key is to respect our frost dates, protect against intense sun, and keep the soil consistently moist.
If you follow this timing for planting herbs in Denver, you’ll have a lush, productive herb garden from spring through fall.
So, get your soil ready, mark your calendar for mid-May, and enjoy the best flavors your Denver herb garden can offer.
Happy planting!