When Is It Safe To Plant Summer Annuals In Montgomery County, MD?

You’ve just walked into the garden center and—bam!—there they are. Bright, bold, blooming summer annuals lined up like candy in a store window. It’s tempting to grab a cart and start planting the moment the first warm day arrives. But hold on.

In Montgomery County, MD, timing is everything.

Planting too early can lead to disappointment—wilted flowers, stunted growth, or worse, a surprise cold snap that wipes out all your hard work. On the other hand, waiting just a bit longer can mean healthier plants, fuller blooms, and a garden that thrives all season long.

So when is it safe to plant your summer annuals in Montgomery County? Let’s break it down.

The Magic Date: When the Frost Is Gone

In Montgomery County, the average last frost date falls between April 15 and April 25. This means that most years, you’re safe to plant your summer annuals sometime after the last week of April.

But keep an eye on the weather. A few warm days in early April doesn’t mean frost is behind us. One rogue cold front can do a lot of damage to tender annuals. A good rule of thumb? Wait until after Mother’s Day, which usually lands around the second weekend of May. By then, the danger of frost is typically gone, and the soil has started to warm up.

Soil Temperature Matters Too

Even if the air feels warm, your soil might still be chilly. And summer annuals are picky—they prefer soil temperatures of at least 60°F. Cold, wet soil can lead to root rot and stressed plants right from the start.

To check your soil temperature, stick a soil thermometer 2–3 inches into the ground in the morning. If you don’t have one, pay attention to nighttime lows. If they’re consistently above 50°F, you’re probably in the clear.

Still unsure? Start with container plantings. Pots warm up faster than garden beds and give you a little more flexibility to move plants indoors if needed.

Best Timeframe to Plant Summer Annuals in Montgomery County

• Late April to Mid-May: This is the sweet spot.

• After Mother’s Day: A reliable seasonal milestone.

• Avoid planting before April 15 unless you’re ready to cover plants or bring containers inside.

By sticking to this window, you give your summer annuals the best possible chance to thrive.

Don’t Skip the Hardening Off Process

If you’ve started your plants indoors or purchased them from a greenhouse, don’t rush them straight into the ground. They need to adjust to outdoor conditions gradually.

Here’s how to do it:

1. Place plants outside in a shaded, sheltered spot for a few hours each day.

2. Slowly increase their time outdoors over 7–10 days.

3. Avoid windy days and direct sunlight early on.

4. Bring them in at night until the lows are consistently above 50°F.

This gentle transition helps avoid shock and sets your plants up for success.

What Happens If You Plant Too Early?

We get it—you’re eager. But rushing things rarely pays off.

Planting summer annuals too early can lead to:

• Cold damage or frostbite

• Stunted growth from chilly soil

• Increased risk of disease in damp spring conditions

• More work protecting them with covers or replanting entirely

It’s better to wait a little and get it right than to rush and have to start over.

Favorite Summer Annuals for Maryland Gardens

When it’s finally safe to plant, here are a few tried-and-true favorites that thrive in our local climate:

• Petunias – Great for full sun and containers.

• Impatiens – Perfect for shady spots.

• Marigolds – Hardy and pest-resistant.

• Zinnias – Love the heat and attract pollinators.

• Begonias – Versatile and easy-going.

• Salvia – Adds height and color to sunny beds.

Mix and match for a colorful, season-long show.

Be Patient, Reap the Blooms

It’s easy to get swept up in spring fever, but a little patience now will lead to a thriving, colorful garden all summer long. In Montgomery County, the safe window to plant summer annuals opens in late April and hits full swing by mid-May. Use the last frost date, nighttime temperatures, and soil warmth as your guides.

When the timing’s right, your summer annuals will thank you—with a season full of color, vibrancy, and beauty that lasts.