Seasonal Pruning

The vernal equinox is really more significant for meteorologists than it is for gardeners. Some plants respond to changes in day length, of course, but they don’t perform differently merely because days and nights are equal in duration.

Still, the vernal equinox (March 19, 2016) is a useful marker for the change from winter to spring.

As the world experiences climate change, scientists who study the seasons (phenologists) are generating more interesting reports about bud break, flower opening, insect emergence, animal migrations and other seasonal phenomena.

We are already witnessing changes in our gardens: for example, my lilacs are blooming earlier than they have in previous years. Lilacs (Syringa vulgaris) typically require a significant chill during the winter months, but decades ago, Walter Lammerts, working at a southern California nursery now known as Descano Gardens, developed three low-chill lilac hybrids: ‘Lavender Lady’, ‘California Rose’ and ‘Angel White’ (pictured). Gardeners in the Monterey Bay area and similar climates can grow Descanso hybrid lilacs and enjoy their fragrance.

Lilac 'Angel White'

Lilac ‘Angel White’

At the same time, my salvias are fading noticeably, earlier than I usually see.

These two garden favorites have markedly different pruning requirements. The lilacs bloom on new wood, so they should be pruned soon after the blossoms fade, before new buds form. This work should be done before June.

Another important maintenance issue for lilacs manages their strong desire to spread through underground runners. When allowed to roam for a few years, a healthy lilac will form a thicket. This may be desirable, depending on the shrub’s location within the garden, but containment might be appropriate. Accomplish this by the straightforward approach of excavating and cutting off the runner that has created the unwanted new growth.

By contrast, salvias can be cut back to about six inches above the ground in early spring, as new growth appears at the plant’s base. Such renewal pruning cleans away the old growth and stimulates vigorous new growth on these garden standbys. The right time for this work will occur in about one month. It is OK to prune earlier before the new growth is evident, but the ideal timing will shorten the least decorative period for your salvias.

A friend, busy with other priorities, saw the traditional season for rose pruning come and go this year, and now asks if she should prune her roses late, or let them go until next year.

The general rule for roses is to prune during the winter months, when the plants are dormant. Still, the popular repeat-blooming hybrid tea roses should be cut back as blossoms fade during the summer months. According to David Austin Roses, this approach will stimulate blossoming and support maintenance of a desirable rounded shape for the plant.

If a missed winter pruning has allowed a rose to compromise its overall shape, the gardener’s strategy should include summer pruning, cutting back stems after blooms fade with shaping the plant in mind, as well as encouraging new growth.

Pruning can be a challenging task for the gardener because of differences in best practices for individual genera. A good pruning book can help to reduce uncertainty, put the gardener in control and make the process easier and ultimately creative.

Enjoy your garden and keep your pruning shears clean and sharp.

Send pruning questions to Tom Karwin

 

Watering Roses in Summer

Q. Dear Mr. Karwin: I can’t find any guidance in my various gardening books on how much water one should give roses after they have stopped blooming (most of mine have), especially between now the beginning of the rainy season. Any suggestions? Many thanks.

August 2013

A. Roses should be watered even after blooming to keep them healthy and growing. This is important during hot summer weather, when the plants could be heat-stressed. Be sure to let them dry out between watering sessions, particularly for roses in containers.

Here is independent advice (unfortunately I lost track of the source):

Summer Watering Tips

Roses like infrequent, deep watering as opposed to watering a little bit every day. They prefer a good deep soak and then like to be dried out before receiving another deep watering.

How do you know if your roses need water in the first place? The leaves may droop and lack the suppleness they normally have.  (Don’t confuse this with the drooping that often occurs when temperatures exceed 90 degrees).

How will you know if you’ve watered too much? The foliage may feel spongy and may turn yellow. If watering from overhead, do so early enough in the day so the foliage has time to dry out before nightfall.  Spraying the leaves with water will often wash away any disease causing spores before they have an opportunity to take hold. So don’t hesitate to do this on a hot, dry day. Your roses will thank you for it!

Best wishes,

Rose Leaves in Winter

Q. I have a question for you about my roses. I live in Pacific Grove, my roses have leaves on them. Should I strip them off or cut below the leaf growth? One of my family members says leave them alone.

December 2013

A. At this time of the year, it’s appropriate to strip leaves from roses to encourage dormancy. Just pull them off by hand and rake up under the rose bush to minimize any disease and over-wintering pests.

Selecting Roses

Local garden centers offer bare root roses for sale at this time of the year. Roses sold as “bare root,” i.e., without soil, are dormant, so they have less weight for shipping, take less space for storage, and need minimal care and feeding. As a result, they are less expensive than roses in nursery containers.

Larger garden centers will stock scores of roses, so list your buying goals. For example, you might want a yellow rose that is highly resistant to diseases. Those factors, color and disease resistance, would help to focus on a short list. Then you could compare the details on the labels of the two roses to learn how they differ.

One difference could be the class of the rose, i.e., Hybrid Tea, Grandiflora, Floribunda, Climber, etc. Roses vary greatly in size across classes, and even within classes, so your new rose should be the right size for its intended location. Definitions of the standard classes are available from Weeks Roses. Browse to www.weeksroses.com, click on “Plants” and then on “Roses by Class.”

An important factor not on the label is the plant’s suitability for growing conditions at the specific spot you have selected in your garden for this rose. Roses typically require ample nutrients, very good drainage and a minimum of six hours of sunlight every day. In addition, some roses will grow better in the particular climate of the Monterey Bay area.

Local garden centers should stock only plants that will grow well in the area around their location, so one approach is simply to trust the center’s buyer.

If you happen to be buying roses while away from your home ground, or looking for a rose you remember enjoying in a different climate, confirm that it is suitable for your garden.

The Monterey Bay Rose Society has recommended roses for local gardens: browse to www.montereybayrosesociety.org and click on “Easy Roses.”

Weeks Roses has recommended roses for the Pacific Northwest Climate, which is north of the Monterey Bay area, but more appropriate than the other climates listed. (The climate of Portland, Oregon, the “City of Roses,” is like that of the Monterey Bay area, but with more rain.) Browse to www.weeksroses.com, click on “Rose Info” and then on “Climate Info.”

If you intend to buy several roses, you might want the American Rose Society’s “2014 Handbook for Selecting Roses.” Browse to www.ars.org, click on “Shop” then on “Books & Merchandise.”

After you have selected one or more roses for your garden, look to the American Rose Society for reliable advice on planting and caring for roses. Brose to www.ars.org., click on “Resources” and then on “Articles on Roses.”

Enjoy your roses!

Uprooting Plants

Recently, as I was digging up four boxwood shrubs, and cutting down a twelve-foot elderberry, I recalled that some gardeners dislike toppling mature plants or discarding healthy ones.

This is not about relocating plants. Certainly, there are situations in which a plant has outgrown its spot, or has failed to thrive because of a lack of sun or moisture or nutrition, or simply doesn’t look right where it is, aesthetically.

In such situations, assuming the plant is not too big to move, go ahead and transplant to a better location within your garden, or gift it to a friend. You and the plant and perhaps your friend will be happier.

We might ask, “When is it a good idea to decommission a plant?”

One justification would be that the plant is both unwanted (for any of several reasons) and too big to move without significant effort or expense.

Another justification arises when an unwanted plant is not too big to move, but no alternative location is available in your garden or in the garden of any friend.

The option that remains is to lift the plant with care and bring it to a garden exchange. These events are constructive and popular when someone steps up to the task of organization.

One should link to the local gardening network to learn when and where a garden exchange will happen. Join a club!

An important mindset when removing a plant is to avoid any sense of loss, and instead to recognize the opportunity to bring in a new and more interesting plant. Therefore, one should have (1) a replacement plant already in mind, (2) the confidence and knowledge to grow the replacement plant, and (3) the patience to let the plant to reach full maturity.

The four boxwoods (Buxus sempervirens) I dug up had been intended to frame a rose bed, but these common plants had grown large enough to block the view of the roses. I will replace them with miniature roses, to be selected.

The elderberry was an unknown species, a gift that I planted before I realized how big it would get, and before I decided to devote that section of the garden to California native plants. A Pacific Red Elderberry (Sambucus racemosa) might have stayed, but this shrub’s berries were not red, but black.

I will replace this shrub with a Silverleaf Manzanita (Arctostaphylus silvicola), a beautiful very gray, and very endangered shrub that is endemic to the nearby Zayante Sandhills. It is also called the Santa Cruz Manzanita. I found a specimen at the Yerba Buena Nursery in Half Moon Bay.  It’s in a one-gallon nursery pot, so it will need time to reach its mature height of eight feet.

Uprooting plants can release space for new botanical treasures.

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Here’s a picture of the Silverleaf Manzanita, from the website of Las Pilitas Nurseries, a treasure trove of information on California native plants, as well as a great source of those plants. There are two locations: Santa Margarita (about 18 miles north of San Luis Obispo) and Escondido.

Arctostaphylos silvicola, Ghostly Manzanita with a beefly. This manzanita is native north of Santa Cruz.

 

Pruning Roses

There’s no need to rush outside to prune your roses, but now would be a good time to prepare for that annual process.

Start by identifying which of your roses are Old Garden Roses, and which are modern roses. The OGRs are once-bloomers, growing on their own roots, while modern roses, e.g., hybrid tea roses, are repeat bloomers, grafted on sturdy rootstock (often ‘Dr. Huey’).

There are numerous rose species, varieties and hybrids, but pruning methods differ greatly between the two broad groups: OGRs and modern roses. Briefly, OGRs bloom on old wood and are pruned in the late summer, after their bloom period and before they set buds. Generally, prune OGRs in a limited manner, removing no more than one-third of the bush.

In comparison, modern roses bloom on new wood, and are pruned more extensively during the winter months, before new stem growth and buds appear in the spring.

Modern roses are hybrids, typically with species that evolved in Asia, where winters are not harsh, so dormancy is related more to winter’s shorter days than to its lower temperatures. In the Monterey Bay area’s moderate climate, modern roses can continue to grow through the winter months without a period of deep dormancy.

Still, even a relatively light dormancy gives modern roses an important rest period, and pruning during this period promotes new stems and large blossoms.

This year, despite December’s record-setting warm spells, we can rely on short winter days to enable our roses to enter dormancy. Defoliation (stripping a rose’s leaves) encourages that process and reduces the potential for continued top growth.

With that background, prepare to prune your modern roses at any time during January or February. The basic techniques have been described and illustrated many times in books and websites, so rather than providing a capsule version of those techniques, I have listed print and online resources on my website, ongardening.com, for your reference.

I will repeat my recent suggestion to relocate your roses, as needed, during the same period. Prepare the new location by digging a hole two to three times as wide as the root ball you expect to have, to support horizontal root growth. The new hole should be only as deep as the existing root ball, to minimize settling of the transplanted rose.

We ready to transplant the rose soak the new location thoroughly. Then, soak the existing rose, lift a good-sized root ball from the bed, and plant it in its new location at the same level as it was in its old location. Water it in.

Now is also the time to select bare-root roses for your garden, so next week I’ll review rose selection and buying.

More

There are many websites with good, free information about pruning roses. Search for “pruning roses” to see several options. Here are some that I found helpful:

All-American Rose Selections

David Austin Roses

American Rose Society (scroll down to the articles on “Pruning Roses”)

If you would prefer a book, look for these more general pruning titles in your local library or bookstore:

Pruning Made Easy – How to Prune Rose Trees, Fruit Trees and Ornamental Trees and Shrubs, by H.H. Thomas (2013)

This book will be published early in February 2014:

Pruning Made Easy – The Complete Practical Guide to Pruning Roses, Climbers, Hedges and Fruit Trees, Shown in Over 370 Photographs, by P. McHoy

More Seasonal Projects

Once we begin to list gardening projects for the fall, ideas keep coming.

As always, it is appropriate to pursue priorities only when the weather is inviting, and to work at a pace that supports your enjoyment of gardening. Seasonal projects can add to spring’s reawakening and the garden’s long-term success, but the plants will survive a little neglect, truth be told.

Prune Fruit Trees

If you are fortunate enough to have one or several apple trees, or other fruit trees, in your garden, they are likely to enter their dormant stage in December. During their dormancy, they should be pruned to produce a variety of benefits. The best practices depend on the kind of tree, its age, whether or not it has been neglected, and the specific reasons for pruning. That’s too many variables for this column, but well worth the tree owner’s research. An excellent source of information is The California Backyard Orchard, a website maintained by the University of California, Davis.

While visiting that website for pruning advice, check out the entry on Pests & Diseases as well. After pruning, seasonal spraying will discourage or eliminate pest and disease problems during the growing season.

The University of California always recommends organic methods, of course.

Sow Wildflower Seeds

This couldn’t be simpler…if it weren’t for the birds. But they can be outsmarted.

Purchase wildflower seeds at your favorite local garden center, or from one of mail order nurseries that specialize in California wildflowers.

  • There are hundreds of California native wildflowers, but retailers will stock popular varieties, e.g., Arroyo Lupine, California poppy, five-spot, baby-blue-eyes, perennial flax, Chinese houses, gilia, bird’s eyes, California bluebell, satin flower, godetia, fiddleneck, tidy tips, beach evening primrose. Any combination of these would provide a pleasing display.

The California poppy, our state flower, is a popular and attractive choice, but be aware that it self-seeds freely and can become a nuisance in the garden.

If you have limited space in your garden, consider planting a swath of wildflowers, to simulate a natural growth pattern. Clear the area of mulch and any weeds, and broadcast the seeds in an informal pattern (not in rows!). Rake the area lightly to make the seeds less visible to our beloved birds, and keep them moist with light watering until the rains begin.

If you have a larger area to seed, you have the opportunity to create a wildflower meadow that will self-seed in future years. The method is essentially same, except on a larger scale.

Another timely task in this season is weeding. We’ll explore that need later.

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We didn’t include any tasks with roses among November’s gardening priorities, because in this part of the year, in the Monterey Bay area, many roses are still growing actively, and even producing blossoms.

Here’s advice from All-American Rose Selections:

“It’s time to do nothing in the rose garden. Well, practically nothing, anyway. We have seen the breathtaking first big, beautiful blooms of summer. And now we marvel at the smaller, but perfect last roses of summer. Enjoy. Roll up the hose. Put away the pruners.”

One rose-related project to pursue without pruning would be prepare to transplant a rose that would do better in another location. (There is at least one such rose in my garden, which is struggling in the shade of an ever-larger Cotoneaster shrub.)

The preparation involves digging a hole in the new location. Dig a hole two to three times as wide as the root ball you expect to have, but only as deep. This will support horizontal root growth without risking excessive settling of the transplanted rose.

Then, wait until January or February, when the rose becomes completely dormant. Soak the new location thoroughly. Then, soak the rose, lift a good-sized root ball from the bed, and plant it in its new location. Water it in.

Dormant Season Only for Plants

Some might regard November as the beginning of the dormant season, with little or nothing for gardeners to do until spring. Not true!

Beginning now, we can pursue selected gardening projects will pay off later in the year. Still, the garden does not demand intensive work and daily dedication by the gardener during this season. It’s quite all right to take time off to celebrate the holidays, avoid nasty weather, and otherwise enjoy life’s many pleasures out of the garden.

There are many good gardening projects to do now in the garden; let’s consider three projects that are worth attention during November.

Plant Cool-season Ornamentals and Edibles

Visit your local nursery for cool-season flowers, e.g., pansies, calendula, candytuft, foxgloves, snapdragons, stock, sweet peas, and sweet alyssum.

Plant seedlings of cool season vegetable such as broccoli, carrots, cauliflower, chard, lettuces and greens, cabbage, potatoes, radishes, peas, bunching onions, and spinach.

Look for six-packs of seedlings at garden centers or farmer’s markets.

Plant Pacific Coast Irises

Several beardless iris species are native to the Pacific coast. Because they cross with each other freely, they are often referred to either as PCIs or Pacific Coast Hybrids (PCHs). Most common locally is the Douglas Iris (I. Douglasiana), named for David Douglas (1799-1834), who was the first botanist to describe this plant as it grew in the Monterey Bay area.

PCIs can be grown from seed, but more often from divisions. After listing a mature PCI clump, pull the stalks apart and store them in water for a few days as they develop white roots at least a half-inch long. Then, plant the divisions and keep them moist until four new leaves appear. Seasonal rains could be sufficient to establish the divisions.

Move Perennials and Shrubs

Plants vary in their ability to tolerate relocation. Roses and hydrangeas, for example, adapt quickly and easily to being moved, although they appreciate careful handling: lifted without being damaged, moved to a hospitable location (full sun for roses; morning sun and afternoon shade for hydrangeas), and watered in.

Generally, it is easy to move plants that tolerate rejuvenation pruning, e.g., abelia, dogwood, honeysuckle, hydrangea, lilac, mallow, penstemon, rose, Rose-of-Sharon, salvia, spirea and many others.

Shrubs with fine root systems, e.g., azaleas and rhododendrons, do not respond well to being moved.

For information on specific plants, search the Internet using the plant’s common or botanical name. Visit ongardening.com for successful search methods.

At this time of the year, plants are dormant, but not gardeners!

More

The Yerba Buena Nursery website has a helpful pruning calendar for California native plants.

The National Gardening Association has brief but solid advice on dividing perennials.

SF Gate has suggestions for adding edible perennials to your garden. Right now is a good time. Some recommended plants might be unfamiliar: tree kale, yacon, ground cherries, chayote and banana passionfruit (Passiflora mollissima). Still, they might be turn out to be welcome new “friends.”

Master Gardener Marie Iannotti, writing on Ask.com, offers a good overview of pruning for several categories of garden plants.

To find information about specific plants in your garden, start by learning their botanical names. (Search ongardening.com for more information on botanical names.)

Then, using Google or another search engine search for the botanical name of the plant, plus “cultivate” or a more specific verb representing want you want to know. Include the variety name, when you know it. Examples:

Rosa minutifolia transplant

Hydrangea paniculata divide

Salvia greggii ‘Heatwave Glimmer’ prune

 

California Native Roses

Rosa Californica is the only rose in my garden that is native to California. It’s a fine plant, but tends to expand its territory through underground suckers.

When I came upon a healthy specimen of another rose identified as a California native, I grabbed it for my garden and worked to learn more about it and other California native roses.

I soon discovered that my new rose, R. multiflora, is an imposter! It is a native to Japan that has become naturalized in California and much of the U.S. In eastern North America, it is considered an invasive species, and even a “noxious weed” in grazing areas. Although it has many blossoms, it is most appreciated by goats.

Roses that are truly native to California typically have single pink flowers, varying degrees of fragrance, and spiny branches. They often are found near water sources. While they tolerate some drought and shade they grow best with ample moisture and sunlight. They can spread vigorously in hospitable circumstances, but are controllable with seasonal pruning.

Here are several species, in roughly north-to-south order.

  • California Rose (R. Californica). Grows in much of California in chaparral, riparian and central oak woodland plant communities. Most widely grown native rose. This photo  is from the website of the University of California, Santa Cruz Natural Reserves.
    Rosa_californica_California_Wild_RoseAs a side note, the UCSC Natural Reserves program includes five sites, including one in Marina and one in Big Creek (south of Carmel). The five sites ring the Monterey Bay along the National Marine Sanctuary that extends the entire coastline from the Golden Gate at San Francisco south to Big Sur, between 38 and 36 degrees North latitude along roughly 122 degrees West longitude.The wide range of habitats, from fog-enshrouded redwood forest to maritime chaparral, provide an unparalleled natural laboratory for marine and terrestrial research and serve as study sites for University scientists and students.
  • Ground Rose (R. spithamea). Native to central California from the San Luis Obispo area up into Mendocino and Humbolt and in the Sierras from Tulare to Yuba. Grows in chaparral and coastal sage scrub plant communities.
  • Nootka Rose (R. nutkana). Grows in riparian areas in northern California and up to Alaska.
  • Wood Rose (R. gymnocarpa). Grows from San Luis Obispo to northern California, and in other western states, and has large fragrant blossoms.
  • Whiskey Rose (R. pinetorum). A relatively rare rose that has been spotted in northern California and in the Monterey area. Resembles R. gymnocarpa.
  • Cluster Rose (R. pisocarpa). A fairly large plant, up to six feet high, with flowers in clusters near the top. Grows in northern California to British Columbia.
  • Mountain Rose (R. woodsii ultramontane). Grows in high elevations east of the Sierras, and produces large numbers of very fragrant dark pink blossoms.
  • Mojave Rose (R. woodsii glabrata). Grows near springs in the Mojave Desert. Similar to R. Californica.
  • Baja Rose (R. minutifolia). Grows in Baja and the southern section of San Diego. It has very small leaves and bright pink flowers with prominent yellow stamens.

The information in this column was drawn largely from Wikipedia and the website of Las Pilates Nursery, a great source of information about California native plants.

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This photo is from Suisun Marsh page of the California Department of Water Resources website. The photo shows Rosa Californica’s rampant growth and numerous rose hips. This plant can be controlled in a garden, through seasonal (and diligent) pruning.

0CCARosehips copy

Garden Priorities for Summer

Last week, regarding summer care of roses, I briefly recommended fertilizing monthly and responding promptly to signs of insect or disease problems. Those are constructive actions, but there’s more that can be done to help your roses to flourish!

Fertilizing roses in the summer is important if they show signs of nutrient deficiency, such as weak growth. Provide a light application of fertilizer with an emphasis on phosphorous.

Recall that fertilizer labels indicate the percentages of the three principal ingredients: N – nitrogen (promotes the growth of leaves and vegetation); P – phosphorus (promotes root and shoot growth); and K – potassium (promotes flowering and fruiting). I have used Dr. Earth’s Rose & Flower Fertilizer (5–7–2), but you could find other very good fertilizers at your local garden center. As always, follow supplier’s recommendations.

Yellowing foliage probably indicates an iron deficiency, which calls for spraying with a liquid iron supplement.

The most common pest of roses is the aphid, which suck the plants juices from buds, stems and the underside of leaves. They can be washed away with a forceful stream of water, or treated with a spray of insecticidal soap, such as Safer® Brand insect killing soap.

I routinely grow Society Garlic (Tulbaghia violacea), which has a garlicky fragrance that seems to confuse or distract aphids. It really works!

Weekly watering will keep roses healthy during the summer months. Water roses at ground level to keep foliage dry and avoid fungal diseases. Use organic mulch to minimize evaporation and discourage weeds.

Deadheading spent blossom will promote new blooms. Cut them off close to a close to a cluster of five leaves; some experts recommend cutting at the second five-leaf cluster, to encourage growth from a stronger stem.

Remove suckers at the base promptly. If possible, pull them off from the rootstock; otherwise, cut them below the soil surface.

***

Deadhead other spring-blooming plants. This practice improves the appearance of the garden, promotes new blossoms from many plants, and reduces the spread of seeds (which might or might not be desired).

Currently, I am deadheading two larger plants: Corsican Hellebore (Helleborus argutifolius) and Mediterranean Spurge (Euphorbia characias, subsp. wulfenii).

Here are Hellebores in full bloom, standing upright.

Hellebores-1 Hellebores-cu2

And here they are laying over:

DSC02465

Here are the Euphorbias, fading:

DSC02469 DSC02468

These plants are quite different but still have common characteristics: they both produce large, dense clusters of flowers on thick stalks that bend over as the flowers fade to drop seeds away from the base of the plant. Both also are prolific self-seeders, if allowed.

At the same time, they produce new growth that limits access to the base of the flower stems. I have found a telescoping pruner to be invaluable in this task. A “cut & hold” model would be ideal.

Enjoy your garden in the summer!