When To Plant Flowers In Delaware

Knowing when to plant flowers in Delaware is the key to a garden that thrives from spring through fall. Getting the timing right means your plants establish strong roots and bloom beautifully, adapted to our unique coastal climate.

This guide breaks down the optimal schedule for annuals, perennials, and bulbs. We’ll cover how to use frost dates and simple tips to make your planting a success.

Delaware’s planting calendar is shaped by its USDA Hardiness Zones, which range from 7a in the north to 7b along the coast. The average last spring frost date is around April 15–30, and the first fall frost typically arrives between October 15–30. These dates are your anchor for all planting decisions.

Spring Planting (After the Last Frost)

This is the main event for most summer-blooming flowers. Tender plants cannot survive a surprise cold snap, so patience is essential.

Annuals (Petunias, Marigolds, Zinnias): Plant these after the last frost date, usually from early to mid-May. They need warm soil and air to grow quickly.
Summer-Blooming Bulbs (Dahlias, Gladiolus, Cannas): These go in the ground at the same time, around mid-May. They love the heat of a Delaware summer.
Warm-Season Perennials (Coneflower, Black-Eyed Susan, Salvia): While established plants are hardy, new perennials do best when planted in May after the soil has warmed up considerably.

Fall Planting (6–8 Weeks Before the First Frost)

Fall is a secret weapon for gardeners. Cooler air and warm soil reduce plant stress and encourage root growth.

Spring-Blooming Bulbs (Tulips, Daffodils, Crocus): Plant these in October through early December. They need a period of cold dormancy to bloom in spring.
Many Perennials and Shrubs: Early September to mid-October is ideal. This gives them time to settle in before winter and they’ll often outperform spring-planted ones.
Hardy Annuals (Pansies, Ornamental Kale): Put these in from late September to October. They’ll often survive the winter to provide early spring color.

Early Spring & “As Soon As Soil is Workable”

Some tough plants can go in before the frost danger is completely over. This means when the soil is no longer frozen or soggy.

Hardy Annuals (Sweet Pea, Larkspur): These seeds can be sown directly in March or early April. They tolerate light frosts.
Cold-Tolerant Perennials (Daylilies, Peonies, Iris): You can plant or divide these as soon as you can work the soil, often in late March or April.

Reading Your Garden’s Microclimate

Your specific yard may have microclimates. A south-facing wall heats up faster, allowing for slightly earlier planting. A low, shady spot might hold frost longer. Observe these areas to fine-tune your schedule.

A Seasonal Flower Planting Calendar for Delaware

Here’s a quick-reference month-by-month guide to keep you on track.

March – Early April

Start seeds indoors for warm-season flowers like tomatoes and peppers (though those are veggies, the principle is the same!).
Direct sow hardy annual seeds if the soil is workable.
Divide and transplant summer- and fall-blooming perennials.

Mid-April – May

Harden off indoor-started seedlings for 7–10 days before planting.
Plant bare-root perennials.
After last frost (mid-May), plant all tender annuals and summer bulbs.
Set out nursery-bought perennial plants.

June – July

Focus on watering, weeding, and deadheading spent blooms.
You can still plant container-grown perennials and annuals, but they will need extra water to beat the heat.
Sow seeds for fall-blooming annuals like zinnias directly in early July.

August – September

Order spring-blooming bulbs for fall planting.
In early September, begin planting perennials, trees, and shrubs.
Divide and replant peonies and iris if needed.

October – November

Plant spring-flowering bulbs.
Plant hardy annuals like pansies for fall and spring color.
Add a layer of mulch around new perennials after the ground freezes to prevent heaving.

Step-by-Step: How to Plant Correctly

Timing is half the battle; proper planting is the other half. Follow these steps for healthy flowers.

Test and Amend Soil: Delaware soils vary. Loosen soil to 12 inches deep. Mix in 2–3 inches of compost to improve drainage and nutrients.
Dig the Right Hole: For potted plants, dig a hole twice as wide as the pot but no deeper. The top of the root ball should be level with the soil surface.
Water Thoroughly: Water the plant in its pot before planting. After placing it in the hole, backfill and water deeply again to settle the soil and eliminate air pockets.
Apply Mulch: Spread 2–3 inches of mulch (shredded bark, leaves) around the plant, keeping it away from the stem. This conserves moisture and suppresses weeds.

Common Mistakes to Avoid

Planting Too Early: Eagerly planting tender flowers in April can lead to frost damage. Wait for reliable warmth.
Ignoring Soil Prep: Poor soil leads to poor growth. Compost is your best friend in sandy or clay-heavy Delaware soils.
Overcrowding: Follow spacing guidelines on plant tags. Good air flow prevents disease.
Forgetting to Harden Off: Seedlings started indoors need a gradual transition to outdoor sun and wind over a week to avoid shock.

FAQ: Planting Flowers in Delaware

What is the best month to plant flowers in Delaware?

For most summer flowers, May is the safest best month after the last frost. For long-term health, September is excellent for planting perennials, trees, and shrubs.

Can I plant perennials in the fall in Delaware?

Yes! Fall is an excellent time to plant perennials in Delaware. The warm soil and cool air encourages strong root development before winter.

When should I plant spring bulbs like tulips?

Plant spring bulbs in the fall, from October through early December. They need cold soil to trigger their spring bloom cycle.

Is it okay to plant annuals in summer?

You can, but container-grown annuals planted in June or July will require diligent watering to establish. It’s better to plant them in the optimal window of May if possible.

How do I protect early-planted flowers from a late frost?

Keep old sheets, frost cloth, or even cardboard boxes handy. Cover tender plants overnight when a frost is forcasted, and remove the cover in the morning.

By aligning your gardening tasks with Delaware’s natural rhythms, you set your flowers up for success. Remember to keep a simple garden journal each year, noting what you planted and when. This personal record becomes your most valuable tool for creating a beautiful, resilient garden that reflects your unique piece of the First State.