11 Container Flower Mistakes That Are Ruining Your Blooms

Container gardening is a wonderful way to bring interest to patios, porches, balconies, and other areas of the landscape. While it's a relatively low-maintenance practice, there are some pitfalls you may encounter when growing flowers in pots and containers. To help you avoid these issues, we spoke to experts who shared the most common container flower mistakes gardeners make and how to avoid them for beautiful blooms.

Using the Wrong Container Size

Using the wrong container size is one of the most common pitfalls people make when growing flowers in pots. "A pot that's too small can restrict root growth, dry out too quickly, and stress the plant," says Tabar Gifford, master gardener and partnership cultivator at American Meadows. "A pot that’s too large can stay soggy around a young rootball and invite rot."

To avoid this, match the container to the plant's mature root system. Most annuals and herbs are happy in 10- to 14-inch pots, while small shrubs and dwarf perennials need 16- to 24-inch pots. "When in doubt, size up just one pot size—not three," Gifford says. If you already planted flowers in a container that's the wrong size, repot the plant to avoid potential issues.

Choosing Containers Without Drainage Holes

Even if you find the most beautiful vessel for your flowers, choosing a pot without a drainage hole will cause problems. "Without an escape route, excess water drowns roots and invites fungus," says Gifford. If you fall in love with a container that lacks a drainage hole, she says to drill one using a masonry bit. Alternatively, you can use it as a decorative outer container and place the plastic nursery pot with drainage holes inside.

Over or Underwatering

Container plants dry out faster than those in the ground, so they need to be watered more often. Gifford says to learn your plant's specific needs and always feel the soil before watering. "You can test the soil moisture by sticking a finger 2 inches into the soil," she says. "If it’s dry, water thoroughly until it runs out the bottom, then let the top inch dry before watering again."

That said, be careful not to overwater, which may cause root rot. "If you start seeing drooping or yellowing leaves, check the soil," says Linda Langelo, horticulture specialist at Colorado State University. "Ease the flowering plant out of the container and check the roots. If the roots are soft and mushy or the stems are soft and mushy, then you have root rot. There is nothing you can do but start over."

Not Providing Enough Sunlight

Plants need adequate sunlight to thrive. "Insufficient light leads to leggy growth and few blooms," says Gifford. "Most flowering plants need six or more hours of direct light. If your planting location is shaded, pick plants that thrive in shade so you’re not disappointed by poor blooms." Be sure to observe the area where your plants will go before making your selections. If you notice that your plants look leggy or wilted, double-check their sun requirements and move them to a more suitable location.

Using the Wrong Soil

Garden soil doesn't have the same composition as potting soil. "Garden soil or heavy mixes don’t drain well in containers, leading to compaction and root issues," says Gifford. "Always use high-quality potting mix designed for containers. You can add perlite or coconut coir to improve drainage and aeration, depending on your plant’s preferences." If you have already planted your flowers in garden soil, repot them using potting soil to avoid root rot and other issues.

Not Providing Support for Climbing Flowers

Vining flowers, like sweet peas or mandevilla, need support even when they're planted in containers or they will sprawl and tangle, causing broken stems. "I’ve lost my fair share of climbing vines that I planted with every intention of coming back to add support later, only to find they were all coiled up together and unable to be untangled without damaging them," says Gifford. She recommends adding a small trellis, bamboo stakes, or even a tomato cage when planting vining plants.

Choosing the Wrong Varieties

Some plants won't thrive in containers, no matter how much attention you give them. "Sunflowers will not reach their full potential in a container because they need space to grow," says Langelo. She recommends considering alternative plants that thrive in containers, such as begonias, marigolds, and petunias. Before choosing varieties, do research to ensure they can thrive in containers. "Look for plants that say 'compact,' 'patio,' or 'container-friendly,'" Gifford suggests.

Adding Too Many Plants

A full planter offers maximum impact, but overfilling it will cause issues for your plants. "The flowering plants will not have enough space for their roots and will compete against each other for nutrients and water," says Langelo. Instead, choose a few complementary plants and give them room to grow. Gifford recommends using the thriller, filler, spiller design, and choosing one focal plant, one or two fillers, and a trailing variety.

Not Repotting Your Plants

Plants outgrow their containers over time and will eventually need a bigger home. "Ignoring this leads to poor growth and declining health," says Gifford. "Perennials and even long-lived annuals will circle the pot, deplete nutrients, and slow growth after a season or two." It's likely time to repot your plants when you notice the soil is drying out faster than usual or roots poking out of drainage holes. Move your plants into a slightly larger container filled with fresh potting mix.

Not Checking for Pests or Disease

Container gardens aren't immune to pests, and it's important to inspect your plants regularly for signs of aphids, mealybugs, and other insects. "Inspect leaves (top and bottom) weekly. Look for signs like sticky residue, webbing, or discolored spots. Address issues early with insecticidal soap or pruning," says Gifford.

Not Fertilizing

Nutrients wash out of pots more quickly because the water drains freely from the drainage holes. "Feed plants every two to four weeks with a balanced liquid fertilizer or slow-release granules, depending on the plant type," says Gifford. "Mix a slow-release fertilizer into potting soil at planting, then supplement with a balanced liquid fertilizer every two to four weeks during peak bloom."

Not Companion Planting

If you're growing multiple flowers together in one pot, Langelo says to make sure you choose varieties with similar growing conditions. "People pick plants that they like without considering that one might like it drier or need more shade than another," she says. "Ask for assistance or research the plants you like. Look for other plants that can be good companions."