In horticultural circles, the term ‘perennials’ is bandied about as if everyone knows what these… Read more
For the professional
The advantages of perennials
Perennials stimulate the senses, improve the urban climate, require little maintenance, and are very attractive to bees and butterflies. A diverse planting that includes many different varieties also has a beneficial impact on our well-being. Public green spaces planted in perennials can thus be colourful, ecologically valuable and easy to maintain.
Perennials make it happen
A colourful look, an enrichment of public space and low management costs: perennials live up to all of these promises. They reappear every spring to begin another cycle of growth and flowering. Some varieties are even evergreen or feature a beautiful winter silhouette. These advantages make a planting plan composed of perennials perfect for almost all situations such as under tree canopies and in verges, parks and roundabouts that require an attractive as well as a long-lived planting.
Low maintenance costs
Landscaping that uses perennials would seem to involve more work and higher costs than a planting that uses plants such as shrubs. Nevertheless, perennials will demonstrate more advantages within a few years due to their low maintenance costs. Many studies have been conducted into long-lived perennials suitable for use in public green spaces. Appropriate varieties include stonecrops (e.g. Sedum ‘Herbstfreude’), yellow coneflowers (Rudbeckia), lady’s mantles (Alchemilla), Japanese Anemone (Anemone hupehensis), Kalimeris, knotweeds (Persicaria), Hardy Jerusalem Sage (Phlomis russeliana) and catmints (Nepeta). Good evergreen groundcovers would include Japanese Spurge (Pachysandra terminalis), Elephant’s Ears (Bergenia crassifolia), Cranesbill (Geranium macrorrhizum) and Caucasian stonecrop (Sedum spurium). Long-lived ornamental grasses for use in public green spaces would include fountain grasses (Pennisetum), moor grasses (Molinia), sedges (Carex) and silver grasses (Miscanthus).
The right place
It is important that the planting location provides for the requirements of the selected varieties, so the soil type, amount of sunlight and the moisture retention of the soil should be considered. If the right plant is chosen for the right location, a healthy, trouble-free planting should remain attractive for at least ten years. Perennials can be used in large groups of the same kind or in combinations. In any case, the goal should be to create a planting that completely covers the soil surface as quickly as possible so that weeds are kept at bay. Making the right combinations will display the plants to even better advantage.
Tips for creating successful perennial combinations:
- Catmints (Nepeta), Hardy Jerusalem Sage (Phlomis russeliana) and fountain grasses (Pennisetum)
- Knotweeds (Persicaria), coneflowers (Rudbeckia) and stonecrops (e.g. Sedum ‘Herbstfreude’)
- Kalimeris, knotweeds (Persicaria) and Japanese Anemone (Anemone hupehensis)
- Caucasian stonecrop (Sedum spurium), Hardy Japanese Sage (Phlomis russeliana) and moor grasses (Molinia)
Perennials can be planted at any time of year as long as temperatures are above freezing, but either autumn or spring are the best times to plant perennials. Perennials begin to grow once the soil starts to warm up in February. The first varieties start to flower as early as March, and the last to bloom can be flowering until the first ground frosts. On average, seven plants per square metre are needed. Small varieties will require 9-11 plants, and large varieties will require 3-5 plants per square metre. Most perennials can be mown with a grass trimmer early in the spring.