Create Depth with a Foreground, Middle-ground and Background
If you have the space, create a foreground, middle-ground and background. Tallest plants go in the back and the lowest growing plants go into the front of the garden bed. This is why you need so much depth in your garden beds.
A Fabric Barrier is the Best Barrier
Purchasing a fabric barrier to prevent weeds in your flower beds is the best way to prevent them from growing.
Arrange in Odd Numbers
Some people are die-hards about organizing items in trios, but any odd number will work for houseplants. If you're after that extremely full and lush plant Instagram look, start by bunching your plants in threes, and then bump up to other odd numbers.
Select Complementary Flowers and Foliage
For example, gardens planted in shades of the same hue, like pink, are pleasing to the eye. Colors next to each other on the color wheel, like purple and red, look good together. So do colors across from each other, like purple and yellow.
If your flower or vegetable bed gets dried out or is exposed to organic matter that increases acidity (such as pine needles), adding fresh topsoil will improve its composition and raise the soil pH closer to neutral. To ensure optimal growing conditions, replenish topsoil as needed.
Over time, mulch will break down and effectively become topsoil but it shouldn't be used in lieu of topsoil. That said, while you could leave your topsoil uncovered, it is wise to cover it with mulch to avoid erosion from the rain and overheating from our hot sun.
Using premium soil is faster and easier than adding compost to your planting beds. On the other hand, if you enjoy hands-on gardening and would rather have complete control over the composition and consistency of your growing medium, compost is probably the right choice for you.
Look online and you'll find that opinions differ when it comes to what soil to put in raised beds. However, it's generally accepted that the optimum raised bed soil mix includes a blend of topsoil, compost and organic matter.
The best way to make planting beds is to keep the soil at or below the original level. Beside the sidewalk it should be 3 inches below the level of the sidewalk so that mulch can be added. Being lower than the lawn grass also works better than being too high.
Keep in Clusters ("the Rule of Three")
Select plants of differing heights for a stronger impact and look for a uniting element to promote a natural vibe. And steer clear of grouping plants with the same textures, shapes, and colors; otherwise, they'll blend into one another.
Three plants creates balance
If you have enough space, group them in an equilateral triangle. This looks particularly good with mounding or vertical plants. Be sure to leave some space between the plants, especially if they are three different kinds.
The most important tip of all in creating a low maintenance flower bed is mulch. If someone asks me for my number one most important gardening tip, it's always mulch. Mulch is a gardener's best friend. After planting your flower garden and watering it well, always apply a 2 – 3 inch layer of a good, shredded mulch.
The Pros of Mulch:
Mulch keeps rain from washing away your soil. As it decomposes over time, bark mulch adds nutrients to your soil. And, maybe everybody's favorite mulch benefit: it discourages weeds from popping up, keeping everything dark so the weed seeds can't sprout.
Your garden will need to receive six or more direct sunlight hours per day, all year. Really though, you're aiming for as much sun as possible. Ideally, you'll position your garden on the south side of any tall structures, such as homes, garages, tall sheds, and fences.
The soil should be loosened to a depth of at least 12-inches for annuals and 18-inches for perennials. Smooth the soil with a ground rake. Plant the flowers at the same soil level as they were in the container. Each year add more organic matter to the soil, or top a bed each year with a 2-inch layer of compost.
As a general rule of thumb, you can aim for a depth of 8'' of fresh topsoil when you start this project. There is nothing magical about the 8'' number, but it's a good starting point and will give you a number to do some calculations with based on the size of your garden.
If you're planning on adding a garden to your landscape, fresh topsoil is a must. The best course of action requires you to mix around 3 inches of topsoil into your garden before planting any flowers. After the topsoil is in place, you'll need to use a tiller to thoroughly combine the garden dirt with the new topsoil.