by Penny Pawl, UC Master Gardener of Napa County
According to a long-term forecast I heard recently, we may not see substantial rain until April and could be facing drought by summer. With that possibility in mind, you can take steps now to help your plants survive.
First, don't rake up those leaves. They protect the soil, help retain moisture and slowly break down and improve the soil.
I cover my vegetable beds with plain cardboard and leaves for the same purpose. Worms adore cardboard glue and will come to the area, add their manure to the soil and aid the soil bacteria. Worm droppings, also called worm gold, is expensive so it's smart to encourage worms in your garden.
If the cardboard has not completely decomposed when you are ready to plant, just cut a hole in the cardboard for the plant. Several years ago, I did an experiment and planted some plants in plain soil and the rest in holes in cardboard that I laid for that purpose. The ones planted in cardboard did better as the soil retained more moisture.
If you have space, dig a few swales. You can make them artful by putting in curves and planting drought-tolerant plants on the edges. When it rains, runoff will be captured in the swales rather than in the gutter and will slowly percolate into the soil. Ideally, runoff should drain in three days to avoid standing water that attracts mosquitos. And your garden will benefit by having water stored a few feet below the soil surface. Some people fill in their swales with sticks, straw or other material and cover them, but I like to see when the swales are full of rainwater.
Do some research on drought-tolerant plants from other regions of the world with a Mediterranean climate. Also consider California native plants, which have evolved to require little water. About three years ago, I planted Pride of Madeira (Echium candicans), which is native to the island of Madeira. I haven't watered it in two years and it just keeps going. Other choices may not be this hardly and may need water occasionally, especially when first planted.
Group plants with similar water needs so you can irrigate more strategically. Sunset's Western Garden Book can advise you on the water requirements of a plant you're considering. You can also find a chart on the water needs of plants at https://arboretum.ucdavis.edu/arboretum-all-stars
Set up a rain harvesting area. I devised two different systems some years ago and both work well. They are attached to downspouts and collect rainwater for use on my plants. I don't have pumps on either system, but I built them higher than ground level so they drain well. Make sure to use screens or other covers where the water collects to foil mosquitos.
When you do irrigate, water deeply. The feeder roots of most plants are deep in the ground. Water that just penetrates the first few inches of soil won't reach the feeder roots on most plants.
If you're designing a new landscape, choose paths over concrete walkways. Paths allow rainwater to soak into the soil. Choose gravel, bark mulch or steppingstones, all of which allow water to penetrate.
And remember to compost, compost, compost. You can make your own or purchase finished compost. Compost is not a great fertilizer, but it improves soil tilth, so your soil will retain more water. Work compost into the soil. In contrast, materials used for mulch should remain on top of the soil to minimize evaporation, keep the soil cooler and control weeds. Weeds will steal water from plants so controlling weeds is important.
Be sure to deadhead most of your spent flowers, although you may want to leave some to benefit the birds. Setting seed takes energy so a plant that isn't deadheaded may require more water.
Napa Library Talks: First Thursday of each month. Register to get Zoom link. http://ucanr.edu/wildlifehabitat2020
Got Garden Questions? Contact our Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to mastergardeners@countyofnapa.org or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email. For more information visit http://napamg.ucanr.edu or find us on Facebook or Instagram, UC Master Gardeners of Napa County.
In Lewis Carroll's Through the Looking-Glass, Alice finds herself in the Garden of Talking Flowers. These flowers are quite outspoken, criticizing Alice's hair, demeanor and general ignorance about their way of life. If my roses could talk, they would tell me how grateful they were for all the rain this spring, and perhaps they would give me a hard time about how grudging I was with that commodity last year.
They would be correct. The goal was to survive, but not necessarily thrive. If your roses are like mine, they are proving their resilience by putting forth a lovely display of flowers right now. But what can we do to keep them healthy and productive for the rest of the season?
First, remember to water your roses during the growing season. This is especially important for roses that bloom repeatedly. Roses that bloom only once a season (usually known as "heritage" or "old garden" roses) do not need a great deal of water once they are established. All other roses need regular watering.
You can use basin watering or drip irrigation. The latter method allows you to water several plants at once. Overhead watering can help wash away aphids and other pests as well spores and mildew. Do it early in the day so the leaves have time to dry. Dampness can encourage fungi. Inspect the plant before watering to make sure you aren't washing off beneficial insects such as ladybugs. Mulching around your roses will keep roots cooler so the plant will need less water.
Fertilize right after each bloom cycle to encourage more flowering. First remove the spent flowers (a practice known as deadheading), then fertilize. Dry fertilizers dug into the ground are effective. Add some compost while you're at it.
If you practice basin watering, you might prefer a liquid fertilizer. Some gardeners spray the leaves directly with a hose-end applicator. Again, do it early and watch for beneficials.
The New Sunset Western Garden Book recommends dehydrated alfalfa as an organic fertilizer because it smells better than fish emulsion. It's also a good way to add nitrogen to the soil.
Even roses that flower only once will benefit from a meal after bloom. They won't flower again, but the nutrients will promote growth in the spring.
As the first bloom fades, you may notice black spots on some rose leaves. Perhaps some leaves have lost color in places or have a powdery white deposit. Black spot, rust and powdery mildew are common rose maladies in Northern California, especially after a wet spring. Rust (Phragmidium mucronatum) is a fungal disease that leaves the top of the leaf discolored, with rust-colored pustules on the underside. Powdery mildew (Podosphaera) presents as a white powdery coating on buds, stems and leaves.
At the first sign of any of these problems, remove affected leaves, stems, buds and flowers. Pick up any fallen leaves or flowers to prevent the disease from spreading. Put the affected foliage in your yard-waste bin--not your compost bin--for the same reason. Many of my own rose woes can be traced to inadequate cleanup.
Both the University of California's "Rose Pest Notes" and the Sunset book recommend spraying to combat these pathogens. Spray the leaves, not the flowers. For rust, use a garlic-based or copper soap fungicide. For powdery mildew, use Neem oil or other horticultural oils, a baking-soda mixture, a copper soap fungicide or sulfur.
Black spot (Diplocarbon rosae) produces black marks with irregular edges on the top of the leaf. Often the leaf turns yellow. Horticultural oils can help reduce black spot. Oils can coat insects—including bees—so apply them at the end of the day when the insects have retired for the evening.
Roses are exuberantly beautiful, and to me that is reason enough to nurture them through their ailments. Give them a little care and they will reward you with color and fragrance well into autumn.
Workshop: Napa County Master Gardeners will hold a workshop on “Rose Care” on Saturday, June 4, from 10 a.m. to noon, at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Join the discussion about spring and early summer rose care, issues and solutions. Learn about integrated pest management for common pests and diseases and how to keep your roses healthy during our current drought. On-line registration (credit card only); Mail-in/Walk-in registration (cash or check only).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
