The yearly regrowth of perennials, the flowering plants that survive for more than one season, gives the gardener a satisfaction that far outlasts the passing color of annuals that live for one season only. In the Napa Valley, fall is the best time to plant perennials, and nurseries have an abundance now. Planting now will give the roots time to become established before warm weather returns.
Many plant societies, botanical gardens and growers have plant sales in the fall. California native plants are always a good choice. Of course, plants don’t have to be native to California to be suitable for Napa Valley gardens.
One of the joys of perennials is their permanence. Many people plant perennials in combination with bulbs and shrubs. Long-lasting perennials can provide a framework for the more fleeting, but vibrant, color of annuals.
Designing garden beds can bring out the artist in you. One of the greatest and best known French Impressionists, Claude Monet, immortalized his garden through his paintings. His garden design followed the same principles as his paintings: light colors predominating and single color masses next to them.
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It is said that Monet first planted a garden to have flowers to paint on rainy days. His garden in Giverny was the inspiration for much of his art. Monet had professional help, but he was not a vicarious gardener. He gave daily orders, inspecting the garden regularly. He would “correct” vistas, order plants to be rearranged and insist on removal of fading blossoms.
Your aesthetic sense doesn’t need to equal that of a famous artist to have a beautiful garden. Begin with soil preparation, an important step for all landscape planting, including perennials. Prepare beds before you go shopping. Apply two to four inches of compost, then dig it in. Add two inches of fresh compost annually, digging it into the soil 6 to 12 inches deep just beyond the plants’ root zone.
If possible, plant perennials on a cool day. Water them well and keep the root ball moist until you see new growth. Slowly taper off the watering and let the winter rains take over.
Perennials need a balance of nutrients, including nitrogen, phosphorus and potassium, along with several trace elements. Phosphorus, the middle number on the fertilizer label, promotes bloom. Apply an all-purpose fertilizer, such as 5-10-5, every spring.
When choosing perennials, aim for variety in color, texture and form. Consider bloom time and foliage appearance. With planning, you can have blooming plants every month of the year. A garden where something is always in bloom is not only attractive, it also offers beneficial insects and pollinators a constant source of food. As a result, these “good guys” are likely to stick around.
Read up on your perennials’ growth habits, and leave room for them to grow. By giving plants adequate space, you allow for air circulation and discourage the development of fungal disease.
Group plants according to their environmental and cultural needs. Place drought-tolerant plants together in dry areas, and put thirstier plants near a water source. This practice is called hydro-zoning.
During the growing season, you will need to weed occasionally, remove spent blooms and control pests.
Group multiples of the same plant for more impact. Plant odd numbers — three azaleas rather than two — to heighten the effect of color and texture. Repeat plants for continuity and harmony. Place shorter plants in front of taller ones, and resist planting in straight rows.
Mulching with a 3-inch-thick layer of organic material, such as shredded bark, will protect your perennials during cold weather.
Some perennials have evergreen foliage that remains on the plant during winter, but many go completely dormant. As the days shorten and grow cooler, these perennials will begin to dry up. Their leaves will turn brown as the plant enters dormancy. These perennials are not dying, so continue to water them. Don’t let them face winter in a dehydrated state. Their roots need moisture to stay strong and healthy.
Avoid planting invasive perennials that displace native species and threaten biodiversity. In our region, ground covers to avoid include periwinkle, English ivy and Algerian ivy. In the shrub category, invasive plants include pampas grass and broom (Scotch, French, Spanish and Portuguese). These plants can be fire hazards. Some nurseries stock invasive plants, so educate yourself before you shop.
Workshop
Napa County Master Gardeners are collaborating with the City of Napa on “Soils and Rainwater and More: A Water-Wise Workshop.” The workshop is on Monday, Sept. 24, 6:30-8:30 p.m. at the Pelusi Building at Kennedy Park in Napa. It will be repeated on Wednesday, Sept. 26, 6:30-8:30 p.m. at Long Meadow Ranch in St. Helena. For information or to register, call 252-4188, ext. 116 or email frances@naparcd.org.
Napa County Master Gardeners (enapa.ucdavis.edu) answer gardening questions Monday, Wednesday and Friday, 9 a.m. to noon, at the UC Cooperative Extension office, 1710 Soscol Ave., Suite 4, Napa, 253-4221.