7 Ways Garden Experts Keep Their Zinnias Thriving All Summer Long

With their vibrant blossoms and layered, intricate petals, zinnias are one of the most cheerful flowers you can sow in your garden. This annual plant typically blooms from late spring to early summer, but with the right care can push through all the way to the first frost of the season.

So what’s the secret to keeping zinnias blooming all summer long and beyond? We asked pro gardeners to share their best tips and tricks so you can enjoy this gorgeous flower as long as possible. 

Water at the Base

Instead of spraying water over the top of your zinnias, give them a good soaking at the base. “Zinnias are susceptible to powdery mildew, especially in humid climates. To prevent this, water early in the day and aim for the soil, not the foliage,” advises Rebecca Sears, gardening expert for Ferry-Morse. She says a drip hose is ideal since it provides even watering at the roots, which can help reduce foliar fungal growth. 

Give Them Space 

To prevent fungal issues, Sears recommends giving your zinnias room to breathe when planting. This allows for improved air circulation and prevents stagnant water or excess humidity. It also allows each plant enough room to grow fully and produce gorgeous, vibrant blooms. 

Zinnias generally need about six to 18 inches of space between plants, depending on the variety. Compact types can be spaced closer (around nine inches), while taller or bushier varieties need more room (about a foot).

Deadhead as Needed 

Deadheading is the process of removing “spent” blooms, and it encourages plants to produce more flowers. If you notice a zinnia blossom is past its prime, go ahead and give it a snip just above the first set of healthy leaves or budding growth. Sears says, “This simple habit can make a big difference in how full and colorful your zinnias stay throughout the season.”

Use the Pinching Technique 

While deadheading removes spent flowers to encourage more blooms, pinching involves snipping off growing tips of young plants. “Pinching is a technique used with many plants; it encourages faster bushier growth for the plant overall but also promotes more blooms,” explains Joshua Salaiz, landscape designer at Moon Valley Nursery. When new growth is emerging from the stems (not flowers), he says you can simply pinch or cut the new growth above a set of leaves. 

Keep an Eye on Pests

Zinnias are prized for being low-maintenance, but just like any garden plant they’re susceptible to pests such as aphids and spider mites. These can quickly sap energy from your zinnias, so it’s important to nix the issue ASAP. Check the undersides of leaves regularly, and if pests are present then apply a gentle spray of insecticidal soap.

Plant Them in Full Sun 

Zinnias thrive in bright, direct sunlight and need ample sunlight daily to deliver A+ blooms, Salaiz says. The more sun they get, the more flowers you’ll see. Plus, sun exposure helps prevent mildew and moisture accumulation on the leaves, which reduces fungal risk. 

Fertilize Your Zinnias Monthly 

This optional step is one of the best ways to keep zinnias blooming all season. “Zinnias are fast growers, and a regular boost of nutrients helps support continuous blooming,” Sears notes. “Use a balanced, all-purpose fertilizer once a month, and you’ll notice stronger stems and more vibrant flowers.”