Foliage is most plants' primary organ for drawing energy from the sun to convert carbon dioxide and water into sugars and oxygen through photosynthesis. In the garden, foliage also contributes to the visual appeal with a variety of textures, shapes and sizes. If the leaves are the typical green, then they can act as negative space - a foil, if you will, against which colourful flowers and structures are highlighted. If the leaves themselves are other than green, then the whole plant stands out. The advantage coloured plants have over flowers is the colour typically lasts most of the season. One common non-green leaf colour is yellow.
In the garden, yellow helps to direct your eye to an area of interest, convincing visitors to investigate and drawing them along a prescribed path. It also helps to brighten an otherwise shady area. Yellow is a great choice to highlight its complementary colour purple, especially in a shady area where purple can literally disappear. Yellow can be combined with the other two primary colours, red and blue, to create interesting colour effects as they play off each other. But a little goes a long way. Avoid creating a circus effect. When working with yellow plants don't forget flowers create periodic and ephemeral contrasts or complements against the foliage.
You have several choices when it comes to yellow plants.
Yellow-leafed spireas (Spiraea spp.) are typically 1.5 to 2.5 feet uniformly globular shrubs with delicate pink, red or mauve flowers in early to mid-summer. Some yellow cultivars produce red leaves to start that mature to gold (e.g. Goldflame). My favourite is Mini Sunglo, aptly named for its shape and bright yellow hue. It will be most colourful in full sun, tending towards limey-yellow in light shade. Tip: trim to four inches in spring to create a perfect mound. Also, give your plants a light shear right after flowering to encourage a second bloom.
Golden hostas (Hosta spp.) come in many shapes and sizes. Hostas in general are shade tolerant. In too much shade, gold hostas will be more lime than yellow. But given too much sun, they can burn. Hostas like evenly moist soil at all times. Their worst enemy is the slug. Golden cultivars include Midas Touch, Gold Standard, August Moon and many, many more varying in size, leaf shape and hue.
Golden ninebark (Physocarpus opulifolious), a medium shrub (four to six feet tall and wide) with shaggy bark, produces not-so-special white flower clusters in early summer. Grow in full sun (for best colour) to part shade. Individual branches may experience winter dieback - just prune these out in the spring. Available cultivars include Luteus and Dart's Gold.
Golden hops (Humulus lupulus Aureus), a vigorous vine that grows 15 to 20 feet, dies to the ground at the end of the season like most perennials. The stems and leaves have short prickles, so wear long sleeves when working around the vines. This vine actually produces hops. If you make your own beer from scratch you could try using your own home grown hops, but I offer no guarantees on the resulting brew.
Finally, there are two dependably yellow junipers. The first one is yellow common juniper (Juniperus communis Depressa Aurea). New growth is bright yellow, fading to bronze in the fall and returning in the spring as lime. The short awl-shaped leaves are sharp and may irritate the skin when brushed against. Reaching 1 to 2 feet tall, it may spread four to six feet if left unchecked. The other juniper is Motherlode (Juniperus horizontalis Motherlode). It is a ground hugger, reaching only six inches tall but spreads to form a dense mat up to 10 feet wide. Both junipers are easily controlled with judicious pruning.
- This column is provided courtesy of the Saskatchewan Perennial Society (www.saskperennial.ca; email: [email protected]).
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