By: Jim Klett, Alison Stoven and Carl Wilson, Colorado State University Extension
With proper choice of low-water use annual and perennial flowers, combined with water-wise garden practices, flowers can be grown with economical amounts of water. The following practices will help keep your flowers healthy while conserving water.
Soil preparation prior to planting will help conserve water
- Prepare soil before planting by loosening soil to a depth of 12 inches. Most Colorado soils, including heavy clay and sandy soil, benefit from adding three inches of compost on the soil surface and tilling to a 12-inch depth.
- Some perennials are more water-efficient than others. Choose your plants to match the site conditions. Many Colorado garden centers are carrying xeric or low water-use flowers.
- Annuals and perennials with gray or silver foliage are often more drought tolerant. Spring bulbs are drought avoiders as they complete their life cycle prior to the onset of hot weather.
Some Drought Tolerant Annuals
- Annual fountain grass – (Pennisetum setaceum)
- Bachelor button – (Centaurea cyanus)
- Cockscomb – (Celosia plumosa)
- Coreopsis – (Coreopsis tinctoria)
- Cosmos – (Cosmos sulphureus)
- Creeping zinnia – (Sanvitalia procumbens)
- Cup flower – (Nierembergia hippomanica var. violacea)
- Dusty miller – (Senecio cineraria)
- Gazania – (Gazania rigens)
- Globe amaranth (Gomphrena globosa)
- Johnny-jump-up – (Viola tricolor)
- Mealy cup sage – (Salvia farinacea)
- Mexican sunflower – (Tithonia rotundifolia)
- Moss rose – (Portulaca grandiflora)
- Periwinkle – (Catharanthus roseus)
- Rocket larkspur – (Consolida ambigua)
- Rudbeckia – (Rudbeckia hirta var. pulcherrima)
- Spider flower – (Cleome hassleriana)
- Sweet alyssum – (Lobularia maritima)
Some Drought Tolerant Perennials
- Artemisias – (Artemisia species)
- Blanket flower – (Gaillardia x grandiflora)
- Blue fescue – (Festuca cinerea)
- Creeping phlox – (Phlox subulata)
- Creeping potentilla – (Potentilla neumanniana)
- German statice – (Goniolimon tataricum)
- Globe thistle – (Echinops ritro)
- Hens and chicks – (Sempervivum tectorum)
- Ice plant – (Delosperma species)
- Lambs ear – (Stachys byzantina)
- Lavender cotton – (Santolina chamaecyparissus)
- Little bluestem – (Schizachyrium scoparium)
- Oriental poppy – (Papaver orientale)
- Ozark primrose – (Oenothera missouriensis)
- Penstemon (Penstemon species)
- Plumbago – (Ceratostigma plumbaginoides)
- Poppy mallow – (Callirhoe involucrata)
- Prairie coneflower – (Ratibida columnifera)
- Prairie dropseed – (Sporobolus heterolepsis)
- Purple coneflower – (Echinacea purpurea)
- Russian sage – (Perovskia atriplicifolia)
- Snow-in-summer – (Cerastium tomentosum)
- Stonecrop – (Sedum species)
- Yarrow – (Achillea species)
- Apply 1-2 inches of organic mulch between flowers to reduce evaporation and control water-stealing weeds. With perennials, this can be permanent mulch like wood chips. With annual flowers, use dried grass clippings so the grass can be turned under after removing the spent annuals following a killing frost in fall.
- Fertilizing perennials is generally not needed if proper soil preparation is done prior to planting. Fertilizer causes lush growth that requires more water. If fertilization is needed, a slow release fertilizer can be applied in the spring.
- Moderate fertilization for bedding plants is recommended either as liquid or granular fertilizer, or a combination of both.
- Annual and perennial flowers under water stress will have drooping leaves and a lack of blooms. Foliage often appears gray-green in color. Water when signs of stress become obvious. Apply irrigation in the evening or early morning between 6:00 p.m. and 10:00 a.m. to minimize evaporation.
- Overhead spray irrigation is the least efficient water-wise method, as much water is lost to evaporation and wind drift. Soaker hoses or drip irrigation are more efficient because they deliver water to the ground level near roots. Hand watering is another alternative that maximizes delivery of water to the soil and roots.
Care with twice weekly water available
- Follow watering programs encouraged or mandated by your community. Disregard for required community watering practices can result in substantial fines and may encourage communities to enact even stricter watering restrictions.
- Annuals and perennials can be watered twice per week if mulched and irrigated deeply to wet the root zone at each application. Annuals require additional water for establishment the first two weeks after planting before cutting back to twice weekly.
- Some flowers will bloom less when less water is supplied. Other xeric (low water using types) thrive on less water.
- Mulching both annuals and perennials is critical to prevent soil moisture loss.
When no water is available:
- Do not plant annuals when outside watering is not allowed.
- Consider planting container gardens if watering restrictions allow hand watering.
- Do not plant new perennials, but mulch existing plants.
After Water is again available:
- Some mulched perennials will survive depending on the length of the “no watering” period. Others may reduce in size or vigor, while others may require replacement. Although the top growth may have died back, water moderately for a few weeks and watch for new growth emerging from below-ground roots.
- Water to keep soils moist, but not saturated, during recovery. Remember that plants reduced in size will not require the amount of water used by large plants with many leaves. Do not overwater; overwatering will add further stress to weakened plants. Dig down and feel the soil to determine when watering is necessary.
- Water perennials well in the fall and monthly during dry winters with no snow cover, to ensure survival during the dormant season. Mulching the crowns of dormant perennials in late fall will prevent frost heaving and conserve moisture through the winter.