By Denise Seghesio Levine, UC Master Gardener of Napa County                                     

Reading about nasturtiums always confused me. Nasturtiums were described as easy to grow and “almost foolproof.” I tried starting them several times to no avail, and yet apparently everyone else knew the secret. This was borne out when my daughter-in-law planted several patches of nasturtium seeds in our garden and growing boxes and they grew. Seemingly easily.

Nasturtium (Tropaeolum minor) is an annual with peppery leaves and spicy flowers. You can find a variety of sizes ranging from tidy eight-inch mounding types to climbing or cascading varieties that can reach five feet in height. Unlike most lush summer plants that appreciate compost-rich soil with plenty of humus, nasturtiums will provide a much more luxurious show of colorful blossoms in sparse soil.  Fertile soil will give you lush green foliage, but you will miss the pops of color that make nasturtiums such a bright addition to the garden.

Nasturtiums are pretty, edible and protective, and they generously self-sow if they find their happy place. So it's worth the effort to get them going, and with Napa Valley weather just now finally warming, you still have plenty of time to get nasturtium seeds in the ground.

Plant nasturtium seeds one inch deep and about ten inches apart. You can plant in clusters of three and thin out all but the strongest seedling or take your chances and plant them singly where they will remain. Most of them will likely come up. Some gardeners like to soak nasturtium seeds before planting to speed germination. If you do, remember to soak them no longer than eight hours to avoid losing your seed to rot.

Nasturtiums like sandy, well-draining soil without too many nutrients, but they do like ample water. If you have planted them in beds, let them dry out a bit between each watering. Nasturtiums planted in pots seem to need watering more often than those planted in the ground and will appreciate a little dilute fish emulsion occasionally to replace the nutrients that frequent watering leeches out. Every site is different, so pay attention to how your plants are doing.  In my garden I have noticed that the plants that volunteer appear to be the most efficient water users.

Nasturtiums have rounded leaves with deep veins radiating from the center. They produce wide, deep-throated single or double flowers in oranges, yellows, creamy whites, maroons and reds. Nasturtiums are pollinator magnets and act as feeding stations for long-proboscis birds and insect nectar seekers. The leaves provide landing pads for a variety of other winged creatures.

Nasturtiums are butterfly host plants, attractive to many varieties as places to lay their eggs. Butterflies will lay their next brood's eggs often on the underside of nasturtium leaves, but sometimes on the top, hopefully hidden from predators. In about 14 days the larva will emerge, turning into caterpillars eating little holes in your garden's leaves.

One of my earliest memories of working at the Master Gardener Help Desk was taking a call from someone who had planted a butterfly garden but had no butterflies. A minute later she told me the other problem she had with her garden that year was an “infestation” of caterpillars, which she had finally eradicated. Unfortunately, those caterpillars would have been her butterflies.

Therein lies a very important lesson: Do not kill the caterpillars if you want butterflies.

But how can you tell which caterpillars are butterflies and which are just eating your cabbage and nasturtiums? The website Gardens With Wings (www.gardenswithwings.com)  has a tool to help identify the butterflies in your garden. Pick the main wing color of the butterfly flitting around your garden and click on the tab.  Up pop pictures of many butterflies. When you see your butterfly, you can see what its eggs look like and what the larva and eventually identifiable caterpillars will look like. It is a fun, useful tool that will help you learn to love caterpillars and to tend, nurture and support our fragile butterfly populations.

Nasturtiums can work in a variety of garden spots from partial shade to full sun. They also act as host plants for aphids, luring them away from your roses, kale and other brassica and cabbage crops. Most plants appreciate having nasturtiums around.

Nasturtiums do really well in our Mediterranean climate. Considered a summer annual, my volunteer nasturtiums were still blooming in December last year and were up and blooming again of their own volition by early May.  Now when people ask me if I grow nasturtiums, I tell them, “Sure, they are easy!”

Next workshop: “Succulents Celebration!” on Saturday, July 20, from 9:30 a.m. to 11:30 a.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Learn why succulents have become the trendiest members of the plant kingdom. For more details & online registration go to http://napamg.ucanr.edu or call 707-253-4221.

The UC Master Gardeners are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.

By T. Eric Nightingale, UC Master Gardener of Napa County

It may surprise you but California has a good deal in common, environmentally speaking, with South Africa. Both have a variety of climate zones, many of which overlap. Many plants from South Africa will grow well in Napa Valley, especially with proper care.

You are doubtless already familiar with some South African plants. Red hot pokers (Kniphofia uvaria), with their spiked yellow and red blooms, are used frequently in Bay Area gardens. Two South African irises, Dietes bicolor and Dieties grandiflora, are present in what seems like two out of three shopping center parking lots. Even the popular bird of paradise, Strelitza reginae, is native to this region.

Many other less-common South African plants will also grow well in Napa. If you are curious about a new plant but unsure if it will grow well in your area, look into its native climate. While the Bay Area has many microclimates, we generally have a warm-summer Mediterranean climate.

This description comes from the Köppen climate-classification system used by many to identify climate zones around the world. You can find a color-coded map online showing areas with similar climates. If a plant comes from an area with the same color code as your garden, it should be a good choice for you. Compare the climate maps of California and South Africa and you will see many of the same colors.

We have native salvias here in California, but Africa also has some members of the genus. A personal favorite of mine is Salvia africana-lutea. It has a pleasant smell and small, dusty-green leaves. The flowers are rust-brown, giving rise to its common name: dune sage. That may not sound appealing, but the blooms and leaves create a color contrast that is attractive in the proper setting.

Another lovely plant in this genus is Salvia dolomitica, conveniently known as South African sage. Its silver-gray foliage makes a background to delicate purple flowers. The calyx—the leaf-like structure that holds the flower—starts out burgundy but turns pink with age. However, my favorite thing about Salvia dolomitica is its fragrance, an intoxicating blend of floral and herbal aromas befitting the plant's elegant appearance.

While some South African plants, such as Dietes, feel so at home here they need almost no help from us, others need a little extra care to remain healthy. Often, this means amending your garden soil to improve drainage or protecting the plant from frost. This is particularly true of plants in the Proteacea family. Leucospermum cordifolium is a shrub that grows large, colorful flowers with extended styles, often called “pincushions”.

A similar plant in the Protea family, the Leucodendron salignum,produces a flower that resembles a pine cone in shape, but in colors ranging from yellow to silver. These plants must have exceptional drainage or their roots will quickly rot. They are also sensitive to frost and can only take low-phosphorus fertilizer. Even though they require this special attention, they are drought tolerant once established. And oh, are the flowers worth the effort!

Many succulents are native to South Africa and will perform well in Napa Valley. Aloe brevifolia is a stubby-leaved, clumping plant that produces orange flowers in fall and winter. It is frost tolerant as well, which is not a common trait in a succulent. Delosperma cooperi, a personal favorite, is a vine-like plant that forms dense mats along the ground and over the edges of planters. It is very cold hardy and produces dozens of pink flowers. When the blooms appear in spring and fall, they will add thick swaths of color to your garden.

Some of the most striking South African plants are bulbs. Freesia, Crocosmia and Gladiolus are familiar, but there are many others. One of my personal favorites is Babiana rubrocyanea, whose flowers have vibrant purple petals with a bright red center. Equally as attractive is Sparaxis elegans, which produces a delicately-colored orange and maroon bloom.

These bulbs are interesting because they thrive in clay soil and are summer-deciduous. During the hot months they die back to the ground and require no water at all. In fact, more than a sprinkling of water in summer will likely cause them to rot. Come spring, however, their leaves return and the flowers burst forth in all their glory.

I encourage you to explore the many plants from South Africa. You just might find a perfect plant for your garden.

Next workshop: “Succulents Celebration!” on Saturday, July 20, from 9:30 a.m. to 11:30 a.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Learn why succulents have become the trendiest members of the plant kingdom. For more details & online registration go to http://napamg.ucanr.edu or call 707-253-4221

The UC Master Gardeners are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.

By Corinne Yoshihara, UC Master Gardener of Napa County

As I traveled through Napa Valley this spring, I made a special effort to note the progression of colors on trees lining my route. Color change (or the appearance of color) occurs every year, yet I never tire of it. It's one of my favorite aspects of spring and it's especially noticeable on trees. I enjoy watching the transformation of stark brown branches to those with pops of whites, pinks and, now, green.

Having had a good winter rain, the flowers were particularly abundant this year (as are the weeds, sigh). I first noticed the white flowers of evergreenpear trees in February. Their white flowers were striking against the grey sky, made even more pronounced by the scarcity of other flowers. Pollen-covered anthers lent a charming speckled appearance to the white petals.

With the landscape being so bare, it was also easy to spot the large white flowers flushed with purple of the saucer magnolia, one of the early blooming hybrids of magnolia. The creamy white flowers of southern magnolia didn't make their appearance until May.

When the February rains took us into March, I noticed more arboreal change. Plum trees were covered with soft pink or white blossoms. Bare maple trees sported flowers resembling little red or yellow-green (red maple and silver maple, respectively) balls of bristles. Also around this time, bright pink pea-like flowers covered the branches and trunk of the redbud tree displaying a trait called cauliflory, or “flowering on mature trunk.”

By April, many more trees were in bloom. I saw striking red clusters of the red horse chestnut flowers, white fringe-tree flowers that resembled dragonfly wings, and crabapple blossoms in colors of white, pink and red.

One tree in particular was especially beautiful in April, the dogwood, one of my favorites. Usually blooming under the dappled light of shade trees just beginning to leaf out, the dogwood's tiered branches are sheathed in white, pink or red depending on the variety. The “flowers” are actually four bracts or modified leaves and the actual flowers are tiny, forming a rounded yellowish cluster in the center of the bracts.

Leaves were out on many trees by May, late spring. It seems like they slowly peep out of their bud covers and then, while you're distracted, cover the entire tree in fresh, unmarred chartreuse. Still, I was able to pick out the flowers of tulip, cherry and hawthorn trees.

The opening of buds raises a lot of questions for the biologist-at-heart. Here is one of mine. Did you notice that many of the earlier flowering trees had no leaves? This behavior of flowering before leafing is called hysteranthous. Although both flowers and leaves begin as buds, flower bud opening is not tied to leaf bud opening.

There are even differences in the times of flowering and leaf unfolding between tree species. Pear, plum, redbud, dogwood, magnolia and cherry trees, for example, all flower prior to leafing. On the other hand, crabapple, horse chestnut and tulip trees have both leaves and flowers at the same time.

Moreover, leaf and flower bud openings can vary within a genus. For example, for the maple genus (Acer), bigleaf maple flower buds open at the same time as its leaf buds; silver maple flower buds open when its leaf buds are still tightly closed; and sugar maple leaf buds open but not its flower buds.

Since flower and leaf bud opening behaviors are not tied, the mechanisms that control them must be distinct. In addition to climatic (chilling, light, heat) requirements, there is a genetic component to flowering. It gets complicated!

Whatever the mechanism may be, it appears that time of flower or leaf opening confers advantages to trees. Trees that produce flowers first, place all of their stored energy into the important process of reproduction before other trees have a chance to leaf out and grow. Also, since flower production, like leaf production, requires sunlight, early flowering ensures that leaves don't block sunlight, or interfere with wind pollination. Masses of flowers may also attract more insect pollinators.

Next time you're outdoors admiring nature's beauty, pay attention to the little things happening around you. You may come up with your own questions. Bring them to the Master Gardeners Tree Walks and share them with us.

The UC Master Gardeners are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.

By Denise Seghesio Levine, UC Master Gardener of Napa County                          

Summer is bold and bright and warm and colorful. Except when it is not. The other side of summer is soft and gray and fuzzy. Bright, bold summer days are often tempered by soft gray fog creeping over the hills and wispy fingers of silver mist drifting through the valley in the morning, cooling and soothing.

In our gardens we can have the same bold and soft summer contrast. Summer is the time when the most colorful flowers show off: golden sunflowers; circus-colored zinnias; blue, white and red petunias; purple foxglove; red and pink asters. Dahlias and roses, lobelias and nasturtium, four o'clocks and cannas can take center stage. 

With so many colors, shapes and scents, we can almost overlook the usually smaller-flowered silver and gray plants. But cool silver and gray are welcome in the garden, especially in our warm summers. Plants with fuzzy silver and gray foliage are made for our Mediterranean climate. 

Why, you may ask? It is the fuzz. Look closely at these plants and you will see soft, tiny hairs covering one or both sides of the leaves. These hairs reflect the sun's rays, slow water evaporation, protect the plant from wind and cool the surface of the leaves by several degrees. Thanks to their fuzz, these understated plants are protected from brutal heat and scarce water. 

Some botanists suggest that the same hairs that protect from heat also insulate from extreme cold and help keep the plant warm in winter. Herbivores are deterred by these waxy or hairy coatings, making these plants deer resistant. A plus for country gardeners. 

At the garden center, it's easy to spot these silvery plants. Look for dusty miller (Artemisia stelleriana) with its lacy foliage. Or lamb's-ear (Stachys byzantina), a perennial with large, soft, fuzzy leaves that children and adults love to pet. Lamb's-ear spreads into a wide gray blanket, producing tall spires of yellow or lavender flowers. 

Yarrows (Achillea ageratifolia), mugwort (Artemisia) and many sages, including Salvia argentea and Salvia officinalis, make beautiful counterpoints to neighboring plants with deep green foliage. Sages range from low-growing groundcovers to towering plants with landing pads for hummingbirds and flowers; many are wonderfully fragrant. The one exception I have found is Mexican sage which grows about three feet tall and produces lovely purple flower spires. It has survived and thrived in my garden for 35 years and looks good most of the year. But it smells terrible. 

Wooly thyme and others in the thyme family belong on any list of gray-, white- and silver-leaved drought-resistant, unfussy plants. About the only way you can kill these plants is with too much kindness. These are not the sort of plants that require abundant water and compost. They will do much better in spare circumstances with scant water. 

If you are perusing seed catalogs, the botanic name will help you identify these plants. White, gray and silver foliage plants have a nomenclature all their own. In Gardener's Latin: A Lexicon by Bill Neal (Algonquin Books),you will find lists with botanic descriptions for the rest of us. 

The phrases alb, alba or albi in a plant's genus or species name all signify white. Candicans, eri, erio and floccosus all describe leaves that are wooly. Argent, argyro and argophyllus mean silver leaved. Greicius and incana refer to gray. Hirsutis, comosis and trychopfollus indicate a hairy plant, and arachnoides means spider-like or covered with long scraggly hairs like cobwebs. See? A whole different vocabulary. Neal's lists are extensive in his useful little book, which is still available if you are so inclined. 

The madrone tree (Arbutus menziesii) provides another interesting example of the reflective qualities of these plants. Its leathery leaves have furry silver undersides that are so reflective that, on country roads late at night, they can be mistaken for oncoming headlights. 

Not every white plant is drought resistant. In nature, plants evolve to survive, but humans now breed plants to be beautiful as well. So be aware that hybridized plants with white foliage may not be as tough as those produced by natural selection. 

Next workshop: “Rose Care” on Saturday, June 1, from 9:30 to 11:30 a.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. For more details & online Registration go to http://napamg.ucanr.eduor call (707) 253-4221.

The UC Master Gardeners are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.