A knot garden is a formal style of landscaping. A traditional knot garden requires planning, grooming, and a fair amount of patience. However, the result is a beautifully symmetrical jewel in your yard. Because a knot garden typically consists of box shrubs used to create geometric shapes, it's best-viewed from above. Choose a flat spot you can see from above, for example a view from a second-story window, and have a charming knot garden planted.
Boxwood shrubs are the foundational plant for a knot garden. In Tudor England, landscape architects used the shrubs to create interwoven designs reminiscent of Celtic knots. That's an ambitious plan, but it would be beautiful if you can enjoy the grand view from a top floor of your home. Such an ambitious plan would require at least consulting with a landscape designer.
However, you could replicate the historical knot garden on a smaller scale. The Tudor-style garden required the box shrubs appear to be weaving in and out. Instead, look at a simple Celtic knot, and make it even simpler by breaking it down to its base geometry. This should yield a pattern of triangles, diamonds, and semi-circles. Use this as the pattern for your modernized knot garden.
Once you have your parterre, which is the system of geometric shrubs, you can either leave the interior empty or fill it with flowers. Naturally, adding flowers adds color and even scent. Since symmetry is a hallmark of knot gardens, you'll want to choose a deliberate plant palette that's repeated throughout the garden.
So, let's say you want to plant beautiful flowers such as zinnia, tulips, asters, and peonies. First, stick within a set color scheme, say only red and white or purple and yellow. As you plan your garden, make sure you balance both colors and flowers. For instance, plant red zinnias in all four corners and white peonies in central triangles. Echo both the red and white with another flowers in a different part of the knot garden.
As Gardening Knowhow points out, knot gardens don't require boxwood shrubs to create the parterre. In fact, you could create a knot garden out of herbs. For this, start with an herbal shrub, such as jumbo rosemary or bay laurel. Use this to create your parterre. From there, choose a set herbal plant palette for symmetry. The site recommends planting the herbs in lines. You could also follow the above technique of filling in the geometric shapes with symmetrical plantings of your chosen herbs.
Design a knot garden to create a beautifully formal effect in your yard. Contact a landscape design professional for more help.