8 common mistakes for new gardeners to avoid

As a garden designer, I often meet with clients who’ve tried to beautify their yard with plants but end up frustrated. A little border along the fence may sit with a few anemic perennials and a half-dead sapling on dry dirt. “We realized we needed your help,” they say.

They tried with good intentions to design a garden, and somehow it didn't work out. I get that. But hiring a professional gardener isn't always necessary. You can create a happy garden on your own as long as you avoid the mistakes novice gardeners often make.

Here are eight of the most common.

Soils are the most overlooked, yet integral element of a successful garden. I often come across detailed advice about amending soils with bone meal and chicken manure, and all else. While this may be useful for more experienced gardeners, simply knowing what kind of soil you have goes a long way toward a garden’s success.

Pick a spot where you want to plant, and, with a full-size shovel (not a trowel), dig up one scoop. From that scoop, take a handful and squeeze. If the soil is reddish-brown and stays clumped together, you probably have clay, which is dense and holds too much water. If it immediately falls apart after a squeeze, you probably have sand, often tan or grayish, which drains too easily. If the clump crumbles after a few seconds and is dark in color, you could have silty or loamy soil, which means it's fairly healthy.

A usually reliable way to fix clay, sandy, or really any soil is to mix in a bag of organic compost for every few square feet of dirt. Compost contains a variety of particle sizes and nutrient-rich organic matter, which helps plants thrive.

Often in client yards, I encounter a shallow border with giant shrubs or a deep border with tiny annuals. If you want that lush, layered look, create a deep border with shrubs at the back and perennials in the foreground. If your yard is small, you can create a shallow border with alternating perennials and a few dwarf shrubs.

Roses like full sun; ferns do not. When you shop for plants, don’t only check the tag, but also ask a nursery employee for placement advice. If you don’t plant the right plant in the right place, it won’t be happy — and neither will you.

“The plant might either die or suffer unnecessarily, grow too large for the space, or be invasive,” says Erin Lau of Erin Lau Design in Seattle.

Dave Whitinger, executive director of the National Gardening Association, suggests mail-order collections as a simple way to get started. “My favorite is Bluestone Perennials,” he says. “They have whole garden collections, and you can pick the theme, and they’ll send you all the plants that are properly grouped for that kind of garden.”

Figuring out how many plants to put in a border is tricky business. New gardeners often plant flowering perennials, then later wonder why the border looks sickly — usually, it’s because they didn’t buy enough for the space. In other cases, they overbought, put the plants in the ground six inches apart, and now the area is a tangled mass of greenery.

When I design, I use markers to stand in for plants before installing them — palm-sized rocks, pots, bamboo sticks, bricks, and irrigation flags all work. My rough rule is to leave two to three feet between shrubs and one foot between perennials. A plant’s label may tell you that less space is fine, but always err on the side of more.

There’s a reason I frequently see roses, lilacs, and mums in newbies’ yards: When they’re in flower, they’re stunning. But tea roses can turn gangly, most lilacs only bloom for one month a year, and mums are amped up on fertilizer every fall so we can deny that winter is coming. Instead of gravitating to flowers (and, believe me, the urge is difficult to resist), focus on foliage.

There are so many interesting variations of leaf shape, texture and color. Some lovely choices include bear’s breeches, heartleaf brunnera, and coral bells.

In winter, plants go to sleep. They lose their blooms and leaves, and turn brown. If you haven't included trees and shrubs, your garden could wind up looking meager and forlorn.

Even small ones create architectural beauty. “I will never tire of witch hazel,” Lau said. “They bloom in the depth of winter — yellow, orange, or red — and they have the most beguiling spicy aroma.” What’s more, small trees and shrubs provide seeds, and hiding and nesting places for birds.

Dogwoods, paperbark maples, and Japanese maples can form not only a design’s backbone but offer interest with fall leaf color, summer flowers, and peeling bark. Shrubs such as spiraea, weigela, and butterfly bush bloom for long periods while adding color to the garden with their foliage.

Large trees are strong and mighty because they’re good at hogging water, nutrients, and space. They have extensive root systems that drain nutrients from the surrounding soil, and their crowns suck up the sun while creating shade for others. This presents a problem: Even a shade-loving perennial won’t thrive if it doesn’t receive its own light, water and nutrients. Install your new plants about a foot beyond the tree’s canopy, amending the soil with compost to further strengthen the plants against the reach of the tree’s root system.

After I’ve installed designs for clients, they often water every few days, then drop off after a couple weeks. Or they wrongly assume one day of light rain is enough to refresh a plant. New plants are babies — they need extra love, particularly if they’re in full sun. When the weather is warm, you’ll probably need to water more regularly than you think necessary. Otherwise, that lovely redbud you planted will slowly turn to a scaffold of dry sticks, and you’ll be out a hundred bucks.