What to Plant in June: Your Summer Microgreens Growing Guide

Quick answer: In June's heat and humidity, focus on heat-tolerant microgreens like sunflower, amaranth, buckwheat, and basil that thrive at 75-85°F temperatures. Avoid cool-season varieties like pea shoots and cilantro, which become bitter and bolt quickly in summer heat. Sunflower microgreens are your best bet, growing faster in warm conditions and ready to harvest in just 7-9 days.

June in Milton brings 85°F days and humidity that can make your growing trays feel like a greenhouse — even indoors.

Most microgreen varieties struggle when temperatures climb above 75°F, but some actually prefer the warmth. The trick is matching your seed choices to summer conditions while managing the extra moisture in the air.

Heat-Tolerant Varieties for June Planting

Sunflower microgreens handle summer heat better than almost any other variety. They germinate reliably at temperatures up to 80°F and actually grow faster in warm conditions — usually ready to harvest in 7-9 days versus 10-12 in cooler weather.

Amaranth thrives in June heat. The seeds germinate at 75-85°F, making them perfect for our Georgia summers. Their deep red stems and leaves add color to summer salads when other greens might wilt.

Buckwheat offers another heat-friendly option. These triangular-leaved microgreens prefer temperatures between 70-80°F and maintain their crisp texture even when grown in warm conditions.

Basil microgreens love summer warmth. While regular basil takes weeks to mature, microgreen basil delivers intense flavor in just 14-16 days when grown at 75-80°F.

Varieties to Avoid in Summer Heat

Pea shoots become stringy and bitter when grown above 75°F. Save these for fall and winter growing when you can maintain cooler temperatures.

Cilantro bolts quickly in heat, turning bitter before you can harvest the tender leaves. The seeds also have poor germination rates when temperatures exceed 75°F.

Most brassicas — including broccoli, kale, and cabbage microgreens — struggle in summer heat. They prefer temperatures between 60-70°F and often develop a sharp, unpleasant flavor when grown warmer.

Managing Summer Growing Conditions

Your biggest challenge in June isn't just temperature — it's humidity. North Georgia's summer humidity can push indoor levels above 70%, creating perfect conditions for mold and damping-off disease.

Run a dehumidifier in your growing space to keep humidity below 60%. This single change prevents more crop failures than any other summer adjustment.

Position your growing trays away from south-facing windows. Even indirect sunlight through glass can push tray temperatures into the 90s, killing seeds before they germinate.

Water less frequently but more thoroughly. Summer heat makes soil dry faster, but higher humidity means water doesn't evaporate as quickly from the surface. Check soil moisture with your finger before watering.

Use a small fan to improve air circulation around your trays. Moving air helps prevent fungal issues and keeps leaf temperatures closer to ambient room temperature.

Step 1: Adjust Your Seed Density

Plant summer varieties 25% less densely than winter crops. Heat-stressed plants need more space for air circulation. For sunflower microgreens, use about 1 ounce of seeds per 10×20 inch tray instead of the typical 1.3 ounces.

Step 2: Modify Your Germination Setup

Skip the blackout period for heat-sensitive varieties. While most microgreens benefit from 2-3 days in darkness, summer heat can turn a covered tray into an oven. Check your trays daily and remove covers as soon as you see green shoots.

Step 3: Time Your Harvests Earlier

Harvest summer microgreens 1-2 days earlier than usual. Heat accelerates growth but can also trigger early flowering or bitter flavors. Amaranth microgreens are particularly prone to this — harvest them as soon as the first true leaves appear.

Seasonal Advantages of June Growing

Summer's longer daylight hours actually benefit microgreen growth once you manage the heat. Most varieties develop more intense flavors when grown with 14+ hours of natural light.

The warm soil temperatures that challenge some varieties help others germinate faster. Sunflower seeds that might take 3-4 days to sprout in winter often germinate in just 24-48 hours during June.

Planning Your Summer Succession

Plant new trays every 5-7 days instead of the typical weekly schedule. Summer's faster growth means you'll harvest more frequently, and the shorter growth cycle helps you avoid the worst heat waves.

Keep notes on which varieties perform best in your specific growing space. Every setup handles summer heat differently — what works in a basement growing room won't necessarily work in a spare bedroom.

By August, you can start planning your fall transition back to cool-weather varieties like pea shoots and brassicas. But for now, embrace the summer heat and grow what thrives in these conditions.

June's challenges teach you more about microgreen growing than any other month. Once you master summer production, you'll handle every other season with confidence.

Other articles from the farm

• Microgreens 101: Everything You Need to Know
• Explore All Microgreen Varieties (Plant Database)
• Recipe: Sunflower Microgreen Salad
• Recipe: Microgreen Pesto

What Most Guides Get Wrong About Summer Microgreens

Most microgreens guides treat summer growing like a scaled-down version of spring planting, but that approach sets you up for frustration. The biggest misconception is that you can grow the same varieties year-round if you just adjust watering schedules.

Here's what actually happens: Cool-season microgreens don't just grow slower in heat — their entire physiology changes. Pea shoots that normally produce tender, sweet leaves will develop thick, fibrous stems when temperatures hit 80°F. The plant rushes to reproduce, skipping the tender microgreen stage entirely.

Another common mistake is thinking indoor growing eliminates weather concerns. Your house might feel comfortable at 72°F, but those black plastic growing trays can reach 85-90°F near windows, even with air conditioning running. Dark-colored containers absorb heat from any light source — LED grow lights, fluorescent fixtures, or indirect sunlight.

Many growers also underestimate how dramatically germination rates drop for cool-season varieties. Cilantro seeds that show 85% germination at 65°F might only hit 30% at 78°F. You're not doing anything wrong — the seeds literally can't handle the heat.

The Seed Company Problem

Seed companies often provide temperature ranges that sound more flexible than reality. When a packet says "60-75°F," most home growers assume anywhere in that range works equally well. In practice, varieties perform best in the lower two-thirds of their stated range.

Broccoli microgreens labeled for 60-75°F growing will be sweet and mild at 65°F, sharp and bitter at 73°F, and nearly inedible at 75°F. That five-degree difference matters more than most guides acknowledge.

Tradeoffs Worth Knowing for Summer Growing

Summer microgreens growing involves several unavoidable compromises. Understanding these tradeoffs helps you set realistic expectations and make better variety choices.

Speed vs. Flavor Intensity

Heat-tolerant varieties like sunflower and buckwheat grow faster in summer — sometimes 30-40% quicker than their spring growing times. But this rapid growth can produce milder flavors compared to slower, cooler-weather development.

Sunflower microgreens grown at 80°F have a pleasant, nutty taste but lack the rich complexity they develop at 70°F. If you're using microgreens as garnish, the speed advantage wins. For dishes where microgreens carry significant flavor weight, you might prefer the deeper taste of slower-grown varieties.

Basil microgreens show the opposite pattern. Heat actually intensifies their essential oils, producing stronger flavor in less time. Summer-grown basil microgreens often taste more peppery and aromatic than their cool-season counterparts.

Convenience vs. Variety

Summer's limited variety selection forces you to get creative with flavor combinations. Instead of growing five different brassicas with subtle flavor variations, you might focus on three heat-tolerant varieties with distinct taste profiles.

This limitation can actually improve your growing skills. When you can only grow sunflower, amaranth, and buckwheat, you learn to perfect each variety instead of spreading effort across marginal performers.

Energy Costs vs. Growing Success

Maintaining ideal growing conditions in summer requires more energy input. Running dehumidifiers, fans, and air conditioning to keep growing areas cool can double your monthly electricity usage during peak summer months.

Some growers solve this by shifting to basement growing during summer months. Basements typically stay 10-15°F cooler than main floors and have lower humidity. The tradeoff is less convenient access and potentially requiring artificial lighting even during daylight hours.

Timing Your June Plantings

June's long days and intense heat create unique timing challenges that require different strategies than spring growing. The key is working with natural temperature cycles instead of fighting them.

Taking Advantage of Overnight Cooling

Even during Georgia's hottest summers, nighttime temperatures drop 15-20°F below daytime highs. This natural cooling period provides the best germination window for heat-sensitive varieties.

Start your trays in the evening, around 7-8 PM when indoor temperatures begin dropping. Place them in the coolest part of your house during their first 48 hours — usually a north-facing room or basement level. This gives seeds the cool, stable conditions they need for strong germination.

For amaranth and buckwheat, this evening start timing can improve germination rates from 60-70% to 85-90%. The seeds anchor themselves during cool overnight hours, then handle the next day's heat much better.

Staggered Succession Planting

Summer's faster growing times allow for more frequent succession plantings, but they require careful timing to avoid overwhelming yourself with simultaneous harvests.

Plant sunflower microgreens every 5 days instead of every 7-10 days used in cooler seasons. Their accelerated 7-day growing cycle means you can maintain continuous harvest without the gaps that often happen with longer-cycle crops.

For slower varieties like basil microgreens (14-16 days), start new trays every 6-7 days. This creates overlapping harvests that provide steady supply without flooding you with more microgreens than you can use fresh.

Heat Wave Strategies

When temperatures hit 95°F+ for multiple days, even heat-tolerant varieties struggle. Plan around weather forecasts to avoid starting new trays right before predicted heat waves.

If you have trays already growing when extreme heat hits, move them to the coolest available location — bathroom floors, basement stairs, even refrigerator tops where the appliance's cooling system creates slightly lower ambient temperatures.

Advanced Summer Growing Techniques

Once you master basic summer varieties, several advanced techniques can expand your growing options and improve success rates with challenging crops.

Pre-Chilling Seeds

Some cool-season varieties become summer-viable with 24-48 hour seed pre-chilling. Store seeds in sealed containers in your refrigerator before planting. This technique works particularly well for lettuce varieties that normally bolt in heat.

Pre-chill lettuce seeds at 35-40°F for 48 hours, then plant immediately in pre-cooled growing medium. Keep trays in the coolest available location for their first 3-4 days. This process can extend lettuce microgreens viability into early summer, though success rates drop compared to spring growing.

Spinach responds even better to pre-chilling. Forty-eight hours at refrigerator temperatures followed by cool-location growing can produce harvestable spinach microgreens even when ambient temperatures reach 80°F.

Evaporative Cooling Setup

Create a simple evaporative cooling system using wet towels and fans. Place damp towels around (not under) your growing trays and position a small fan to blow air across the wet fabric. This can reduce local temperatures by 5-8°F through evaporation.

Change towels every 2-3 days to prevent bacterial growth. This technique works best in lower-humidity conditions — when relative humidity exceeds 70%, evaporative cooling becomes ineffective.

Modified Blackout Periods

Extend natural blackout periods for heat-sensitive varieties by keeping them in dark, cool locations for an extra 12-24 hours beyond normal recommendations. This slower development pace helps prevent heat stress during the critical early growing phase.

Buckwheat microgreens normally need 2-3 days of darkness, but extending this to 4 days during summer heat waves often produces stronger, more flavorful final crops. The extra day of root development helps plants handle subsequent heat exposure.

Ice Cube Watering

For established trays showing heat stress, place 2-3 ice cubes at the corners of growing trays during the hottest part of the day. As they melt, they provide both cooling and gradual hydration without shocking plant roots.

This technique works best with larger microgreens like sunflower shoots that can handle slight temperature variations. Avoid using ice with delicate varieties like basil that prefer consistent conditions.