It goes without saying that water is essential for healthy, blooming roses. It is also a given that California faces a drought crisis. Last month Gov. Gavin Newsom issued a directive mandating water conservation. We must be good, conscientious citizens and reduce our water consumption. We must also take care of our roses and not overwater them.
Fortunately, by taking steps to avoid wasting water and making sure every drop of water counts, we can meet the challenge of these two competing and crucial imperatives.
water and plant health
Water is drawn from the soil by the roots and distributed throughout the plant. It is essential for transporting nutrients to the plant and for photosynthesis. The stomata, tiny openings on the underside of the rose petals, cool the plant in a process called transpiration. This shedding of water by the leaves creates the “pull” that causes water uptake by the roots. When there is insufficient water in the soil, the stomata close to conserve water. The result is a decrease in photosynthesis, causing the plant to produce fewer and smaller rose flowers. Eventually, the plant will stop producing new growth and may become more susceptible to pest infestations and fungal diseases.
Plants need more water when it’s hot. Ideally, during the summer months we would extend our watering runtime and/or add an extra watering day. In a drought, we must instead consider the steps we must take to maximize our limited water allocation and minimize plant stress.
Every drop of water counts
There are many variables that affect the water needs of our plants. These include the growing season, temperature, wind conditions, the size of the plant and the composition of our soil and how well it holds water. Plants that have been lightly watered daily are at a disadvantage as they have shallow roots. Roses that are watered less frequently but over longer periods develop healthy, deep roots. This is especially important during drought conditions as it allows the plant to absorb more moisture from the soil, keeping it cooler and more hydrated.
How to determine the minimum amount of water your roses need: Water early in the morning and measure how long it takes to wet the entire root system of the plant. Don’t water again until the soil feels dry to the touch more than 2 inches deep, but don’t stress the plant by waiting to see wilted or drooping leaves and flowers.
One activity, multiple benefits: Heat and wind stressed plants should be given some relief by dousing their leaves with water. While this measure is not an efficient form of water protection, it has a dual purpose as water jetting is one of the tools of integrated pest management to keep pests like spider mites and aphids at bay. Avoid doing this during the hottest hours of the day to minimize water loss through evaporation, but allow adequate time for the leaves to dry before nightfall to avoid water-borne fungal diseases.
Plant cooling system: In summer, we avoid cutting long stems when removing flowers or bringing flowers indoors, as the leaves cool the plant through transpiration. They also shade the soil and reduce water loss. On the other hand, since taller plants use more water, you might consider trimming the height of your taller roses during a drought.
Don’t waste water
Use an irrigation system that saves water: Drip irrigation systems like Netafim, which consist of hoses with evenly spaced internal emitters, are the most efficient water supply system. They save a lot of water by releasing water at a much slower rate, typically 1 gallon or 2 per hour per emitter, and every drop of water is delivered directly to the plant’s root zone. The soil absorbs the water without waste and runoff, allowing the plant to utilize every drop. In contrast, a sprinkler system’s water output is a gallon or 2 PER MINUTE. These overhead sprays can lose up to 50 percent of water through evaporation. Also, unlike a drip system, which is placed in a grid or circle around each rose, there is no precision in water delivery with a sprinkler system.
Turn off irrigation when it’s going to rain: If you can’t remember, install a smart water meter. Our former president of the American Rose Society, the late Bob Martin, liked to joke that there’s little that quite compares to that silly feeling you get on a rainy night when you hear the automatic watering system turn on.
Watch out for poor water management: Does your lawn get soggy and your soil soggy after you water? This is an indication that you are applying more water than your soil can handle.
Check your watering regularly: Fix broken or clogged emitters, disconnected hoses, pup-chewed drip lines, and leaking faucets and hoses. Adjust your sprinkler heads if your walkway, sidewalk, and gutter are pointlessly watered when watering.
Prioritize plants: Don’t waste water on underperforming roses and plants. “Shovel” them and save the water for the roses and plants you cherish. Prune or remove companion plants that are blocking water intended for your roses.
Balance water consumption: Roses are not “water smart plants,” but a healthy garden has a variety of plants, including drought-tolerant plants. Lawns are the biggest water guzzlers and can account for half of a home’s water use. Consider removing the lawn or part of it.
Reduce indoor water consumption and use the water you save indoors for your plants.
Fertilize less in summer to save water and control pests: Fertilizers stimulate growth, new growth requires more water, and tender new foliage provides a real treat for summer pests like chili thrips. Last year I applied a granular organic fertilizer at the end of June and stopped fertilizing until the end of September. My plants stayed healthy and had fewer pests.
Mulch: A 3 or 4 inch layer will prevent weeds from germinating that will compete for the water intended for your plants. This layer of mulch, placed on top of in-line drip irrigation, also minimizes water loss through evaporation and moderates soil temperature, reducing root stress.
This summer we face two challenges: minimizing our overall water use and maximizing every drop to allow our plants to thrive. Both goals can be achieved with well thought-out and clever water management.
Perwich is a member of the San Diego Rose Society, a consulting Rosarian, and a master gardener with the UC Cooperative Extension.