Colorado’s high altitude and cool nights actually benefit arugula, allowing for extended spring planting. Finding the best time to plant arugula in Colorado depends on your specific region and the unpredictable mountain weather. This guide will walk you through every detail so you can enjoy fresh, peppery leaves from your garden.
Arugula thrives in cool weather, making it a perfect crop for Colorado gardens. The key is to plant early enough to beat the summer heat but late enough to avoid a hard freeze. Let’s break down the timing for each part of the state.
Best Time To Plant Arugula In Colorado
The ideal window for planting arugula in Colorado is from late March through early May for spring harvest. For a fall crop, aim for late July through early September. This timing takes advantage of the cool soil and air temperatures that arugula loves.
Colorado’s climate varies widely. The Front Range, Western Slope, and high mountain valleys all have different last frost dates. Your local microclimate matters more than a general state-wide date.
Spring Planting Window
Start planting arugula seeds outdoors as soon as the soil can be worked in spring. The soil temperature should be at least 40°F, but 50-65°F is ideal. Arugula seeds can germinate in soil as cold as 35°F, though it will be slower.
- Front Range (Denver, Boulder, Colorado Springs): Late March to mid-April
- Western Slope (Grand Junction, Montrose): Early March to early April
- High Mountains (Leadville, Breckenridge): Mid-May to early June
- San Luis Valley (Alamosa): Late April to mid-May
For a continuous harvest, plant a new batch of seeds every 2-3 weeks until the weather gets consistently warm. This is called succession planting. It ensures you have fresh arugula all spring.
Fall Planting Window
Fall arugula often tastes sweeter because cool temperatures reduce bitterness. Plant seeds 6-8 weeks before your first expected fall frost. In most of Colorado, that means late July to early September.
- Front Range: Late July to mid-August
- Western Slope: Early August to early September
- High Mountains: Late June to mid-July
- San Luis Valley: Late July to mid-August
Arugula can handle light frosts and even snow. In fact, frost improves the flavor by converting starches to sugars. You can often harvest well into October or November with some protection.
Soil Preparation For Success
Arugula grows best in well-drained soil rich in organic matter. Colorado soil is often clay-heavy or sandy, so amending is key. Work in 2-3 inches of compost before planting.
Test your soil pH. Arugula prefers a pH between 6.0 and 7.0. Colorado soil tends to be alkaline, so you might need to add sulfur or peat moss to lower the pH.
Rake the soil smooth and remove rocks. Arugula seeds are tiny, so a fine seedbed helps with germination. Water the soil lightly before planting to settle it.
How To Plant Arugula Seeds
Sow seeds directly in the garden about 1/4 inch deep. Space seeds about 1 inch apart in rows 10-12 inches apart. You can also broadcast them in a patch for a cut-and-come-again harvest.
- Make a shallow trench with your finger or a stick
- Drop seeds every 1/2 to 1 inch
- Cover lightly with soil or vermiculite
- Water gently with a fine spray
- Keep soil consistently moist until seeds germinate (4-7 days)
Thin seedlings to 4-6 inches apart once they have two sets of true leaves. Thinning is important for good air circulation and larger leaves. You can eat the thinnings in salads.
Watering In Colorado’s Dry Climate
Arugula needs consistent moisture to grow tender leaves. Colorado’s low humidity and intense sun can dry out soil quickly. Water deeply once or twice a week, depending on weather.
Check soil moisture by sticking your finger an inch into the soil. If it feels dry, it’s time to water. Mulching with straw or grass clippings helps retain moisture and keeps roots cool.
Drip irrigation or soaker hoses work best. They deliver water directly to the roots without wetting the leaves, which reduces disease risk. Avoid overhead watering in the evening.
Sunlight Requirements
Arugula grows best in full sun, but in Colorado’s intense summer heat, partial shade is better. Plant in a spot that gets 4-6 hours of sun per day, especially morning sun.
In spring and fall, full sun is fine because temperatures are cooler. If you plant in summer, choose a location that gets afternoon shade. This prevents bolting and bitterness.
Consider using shade cloth if you’re planting in June or July. A 30-40% shade cloth can extend your harvest by several weeks. You can also plant arugula on the north side of taller crops.
Fertilizing Arugula
Arugula is a light feeder, but it benefits from a little nitrogen. Apply a balanced organic fertilizer at planting time. Fish emulsion or compost tea work well as a side dressing.
Too much nitrogen can make leaves tough and overly spicy. Stick to a light application every 3-4 weeks. If your soil is rich in compost, you may not need any fertilizer at all.
Watch for signs of nutrient deficiency. Yellowing leaves may indicate a need for nitrogen. Stunted growth could mean poor soil structure or pH issues.
Common Pests In Colorado
Flea beetles are the most common pest for arugula in Colorado. They create small holes in leaves. Use row covers right after planting to keep them out.
Aphids can also be a problem, especially in spring. Spray them off with a strong stream of water. Ladybugs and lacewings are natural predators that help control aphids.
Slugs and snails appear in wet weather. Hand pick them at night or use diatomaceous earth around plants. Keep the garden clean of debris where they hide.
Harvesting Arugula
You can start harvesting arugula when leaves are 3-4 inches long, usually 3-4 weeks after planting. Pick outer leaves first, leaving the center to keep growing. This method gives you multiple harvests.
For a cut-and-come-again approach, use scissors to cut the whole plant about 1 inch above the soil. It will regrow for another harvest in 2-3 weeks. You can do this 2-3 times per planting.
Harvest in the morning when leaves are crisp and full of water. Rinse gently and pat dry. Store in a plastic bag in the refrigerator for up to a week.
Extending The Season
Use cold frames or row covers to plant arugula earlier in spring and later in fall. These simple structures trap heat and protect from frost. You can start seeds 2-3 weeks earlier with protection.
In winter, arugula can survive under a cold frame or in an unheated greenhouse. Some Colorado gardeners grow it all winter with minimal protection. The flavor is excellent after a frost.
Consider growing arugula in containers. You can move pots to sheltered locations when weather turns extreme. Containers also warm up faster in spring, giving you an earlier start.
Best Arugula Varieties For Colorado
Choose varieties that are bolt-resistant and adapted to cool conditions. Standard arugula works well, but some hybrids perform better in Colorado’s climate.
- ‘Astro’ – Fast growing, mild flavor, good for spring
- ‘Sylvetta’ – Wild arugula, more heat tolerant, spicier
- ‘Wasabi’ – Extra spicy, great for fall
- ‘Apollo’ – Slow to bolt, good for succession planting
- ‘Dragon’s Tongue’ – Pretty purple veins, mild taste
Try a mix of varieties for different flavors and harvest times. Some are ready in 20 days, others take 40. This gives you a longer harvest window.
Companion Planting Tips
Arugula grows well with many vegetables. Plant it near carrots, onions, and lettuce. It also helps repel pests from tomatoes and peppers.
Avoid planting arugula near strawberries or other brassicas like cabbage and broccoli. They compete for nutrients and attract similar pests. Keep arugula in a different bed each year to prevent soil-borne diseases.
Plant arugula as a living mulch under taller crops. It shades the soil and suppresses weeds. Just make sure it gets enough light to thrive.
Troubleshooting Common Problems
If your arugula bolts (goes to seed) quickly, it’s likely too hot or stressed. Plant earlier in spring or later in fall. Provide shade and consistent water to delay bolting.
Bitter leaves are usually a sign of heat or drought stress. Harvest in the morning and water regularly. Older leaves are more bitter than young ones, so pick often.
Yellow leaves can indicate overwatering or poor drainage. Colorado clay soil holds water, so make sure your bed drains well. Raised beds help with drainage in heavy soil.
Leggy growth means the plant isn’t getting enough light. Move to a sunnier spot or thin plants to reduce competition. Arugula needs at least 4 hours of direct sun.
Using Arugula In Your Kitchen
Arugula is versatile in the kitchen. Use it fresh in salads, on sandwiches, or as a pizza topping. It also wilts nicely into pasta dishes or soups.
Try arugula pesto as a change from basil. Blend arugula with garlic, nuts, Parmesan, and olive oil. It’s peppery and delicious on pasta or bread.
Arugula can be sautéed like spinach. Heat olive oil, add garlic, then toss in arugula until just wilted. Season with salt and lemon juice for a quick side dish.
Store arugula properly to keep it fresh. Wrap in a damp paper towel and place in a plastic bag in the crisper drawer. Use within 5-7 days for best flavor.
Fall And Winter Care
In late fall, cover arugula with a thick layer of straw or leaves. This insulates the soil and protects plants from hard freezes. You can harvest through early winter with this method.
If you have a cold frame, plant arugula in September for winter harvests. Open the frame on sunny days to prevent overheating. Close it at night to trap warmth.
Some Colorado gardeners grow arugula indoors in winter. Use a sunny windowsill or grow lights. It’s slower growing but still productive in cool rooms.
Frequently Asked Questions
Can I plant arugula in summer in Colorado?
It’s possible but challenging. Choose a heat-tolerant variety and provide afternoon shade. Expect smaller leaves and more bitterness. Succession planting every 2 weeks helps.
How late can I plant arugula in fall?
You can plant as late as early September in most areas. With protection like row covers, you can plant into October. Arugula can survive light frosts easily.
Does arugula come back every year?
Arugula is an annual, not a perennial. It completes its life cycle in one season. However, it self-seeds readily if you let some plants go to flower. You’ll get volunteer plants next spring.
What temperature is too hot for arugula?
Arugula stops growing well above 80°F. Leaves become tough and bitter. It will bolt quickly in sustained heat. Stick to spring and fall for best results.
Can I start arugula indoors?
Yes, but it’s not necessary. Arugula transplants poorly due to its delicate roots. Direct sowing is easier and more reliable. If you start indoors, use peat pots to minimize root disturbance.
Final Thoughts On Timing
Colorado’s unique climate is actually perfect for arugula if you time it right. The cool nights and bright days produce leaves with excellent flavor. Don’t be afraid to experiment with planting dates.
Keep a garden journal to track your planting dates and results. Over time, you’ll learn the best window for your specific location. Microclimates vary even within the same city.
Remember that arugula is forgiving. Even if you plant a bit early or late, you’ll likely get a harvest. The key is to avoid the hottest part of summer and provide consistent moisture.
Start with a small patch and expand as you gain confidence. A 4×4 foot bed can provide enough arugula for a family of four. Succession planting ensures you never run out.
Enjoy the process of growing your own food. There’s nothing quite like fresh arugula from your Colorado garden. The peppery bite is a reward for your effort.