There are lots of good reasons for mulching your flower garden. Covering the soil with a layer of mulch helps control weed growth, reduce moisture loss and moderate soil temperature. In winter, mulch helps to insulate the root zone and protect your perennials from extreme cold.
In a flower garden, mulch also has aesthetic value. Gardens always look better when framed by a lawn that’s lush and neatly trimmed. A carpet of mulch works in a similar way to set off your plants and make the entire garden look more pulled together.
Best Mulch for Flower Gardens
A vegetable garden can be mulched with just about anything — from carpet remnants to black plastic. Flower gardens call for more restraint. The best mulch for flower gardens is neutral in color so it doesn’t compete with the flowers. Black and dark brown make the plants really pop.
You also want a mulch that’s finely textured so it doesn’t look rough and messy, and so it’s easier to spread around plants of many different shapes and sizes. Here are the mulch materials that work best for flower gardens:
Compost (made from kitchen and garden scraps or well-rotted animal manure)
Leaf mold (moist and crumbly, partially decomposed leaves)
Shredded leaves (leaves that are dry and in pieces)
Cocoa shells or buckwheat hulls
Salt hay or seaweed
Over time, these organic mulches will gradually break down into the soil and need to be reapplied. Whenever you add fresh mulch, be sure to check the depth so the layer is never more than about 2” thick. If mulch gets much thicker than that, it can start to deflect rain and overhead irrigation, depriving plant roots of both moisture and oxygen. A thick layer of mulch is also an appealing environment for voles and other pesky rodents.
Which Mulches Are Not the Best for Flower Gardens?
Shredded bark, sawdust, wood chips and bark nuggets are generally not recommended for flower gardens. These high carbon materials are fine for landscaping, but as they break down, they can alter soil pH and reduce nitrogen levels. Perennials are not heavy feeders, but the loss of soil nutrients can reduce their growth and vigor.
Pine needles (pine straw) are an attractive mulch, but are also naturally acidic. Reserve them for mulching around acid loving-plants such as azaleas and rhododendrons. Well-rotted straw can be a good mulch, but the texture is clumpy. This makes it difficult to spread and the appearance can be too rough for a flower garden.
Dry grass clippings can be an OK mulch if your lawn has not been treated with chemicals. But if you live in a rainy climate, the clippings can fuse together into a dense, soggy mat that inhibits the movement of air and water.
Polyester weed fabric and black plastic are also not recommended for flower beds. These materials are OK for mulching large landscaped areas, but difficult to use in a flower bed. The growth of shallow-rooted perennials can also be inhibited when they are surrounded by fabric or plastic mulch. Shredded rubber mulch, lava rocks and stone are also not recommended. As plants are moved in and out of your flower gardens, these materials inevitably get mixed into the soil.
Other Factors to Consider When Choosing Mulch for a Flower Garden
Weather. In hot climates, perennials benefit from a loose, relatively dry mulch such as shredded leaves. These high-loft materials trap air and help insulate roots from extreme heat. Where summers are cool and rainy, shredded leaves, compost and leaf mold are good options because they don’t get soggy in wet weather. This means fewer problems with fungal disease and pests like slugs and earwigs. In cold climates, give the soil some time to warm up in the spring before applying mulch.
Soil Type. If the soil in your flower garden is heavy and poorly drained, avoid thick, moisture-retentive mulches. It’s important for the soil and the roots of your plants to breathe. If your soil is sandy or stony, mulching with compost or shredded leaves is doubly good. As these materials decompose, they will add nutrients and organic matter to the soil and help improve water retention.
It’s also good to know if the soils in your area are typically acidic or alkaline. Shredded leaves and compost can help to moderate pH issues, while materials such as pine straw and certain types of bark mulch can exacerbate them.
Tips for Mulching Flower Gardens
• When mulching perennials, keep the material an inch or two away from the crown of the plant. Trapping moisture against the stems can invite pest and disease problems.
• Be careful when mulching around peonies. These perennials sprout from roots that lie just below the soil surface. Covering the surface roots with more than 1 or 2” or soil or mulch can reduce or inhibit flower production.
•Ground covers and other low-growing perennials can be used as a living mulch. Examples are creeping phlox, sedum, candytuft, ajuga and liriope. Other low-growing perennials that can blanket large areas include bergenia, black mondo grass and lamb’s ears. These plants are not an all purpose solution, because they need to work with the garden design and be compatible with neighboring plants. But they can be extremely effective.
• In a densely planted flower garden you can often get away without using mulch. Once the plants leaf out, the foliage creates a canopy of shade that reduces moisture loss and controls weed growth.
For other ideas, you may be interested in reading: How to Control Weeds in Your Flower Garden