Repotting a Container Plant

At a recent talk by a skillful gardener, I learned new techniques for repotting plants in containers.

First, let’s review the usual approach to this routine process.

When a plant has outgrown its container, the goal for repotting is to encourage and support the plant’s further growth.

The signs that a plant has outgrown its containers include roots growing out of the drainage hole, or roots filling the container (observed after lifting the pant from its container), or an abundance of multiple shoots or offsets. Additional signs of a pot-bound plan: a plastic nursery pot might bulge with the plant’s roots, or the soil in the container dries out quickly.

When the gardener observes the beginnings of such signs, it is time to remove the plant from its container and replant it in a larger container with fresh potting soil and irrigate to settle the soil around the roots. The common wisdom is to move the plant into the next larger container, e.g., from a one-gallon pot to a one-and-one-half gallon pot.

When a plant becomes significantly root-bound, however, good practice calls for root pruning. If roots have been circling the pot, cut through the roots with a hand pruner, and in some cases, peel away the outer layer of roots. If the roots are packed tightly in the pot, loosen the roots, cut away up to one-third of the roots, and make vertical cuts about one-third of the way up from the bottom of the root ball. These actions will stimulate the growth of new roots.

When reducing the root ball in this way, it could be appropriate to replant the plant in the same pot it had outgrown. This might be desirable when the gardener favors the container, or the container complements the plant nicely.

During this process, cut back a proportionate amount of the top growth to reduce the plant’s demand on its reduced root structure. In a short time, the plant will recover from repotting and resume vigorous growth.

Briefly, these are the usual steps to take to rescue a root bound plant and help to continue growing.

Then, Keith Taylor’s eye-opening talk and demonstration for the Monterey Bay Area Cactus & Succulent Society introduced different goals and techniques for repotting plants.

Medusa Plant by Keith Taylor

Taylor has been growing cacti and succulents for about twenty-seven years, with a previous background in bonsai cultivation. He has developed bonsai-related techniques for cultivating succulents, with an emphasis on caudiciform plants. Those are plants that develop a swollen trunk, stem or root—called a caudex—that stores moisture. These unusual plants are candidates for bonsai treatment and often favored by collectors.

(Note: The specimen shown here is a Euphorbia, which is not a caudiciform.)

Instead of repotting plants to encourage and accommodate growth, Taylor seeks to limit their size, promote larger and wider caudices, and stimulate compact top growth.

In pursuit of these goals, Taylor’s distinctive approach to repotting includes severe pruning of the plant’s roots and top growth. Without hesitation, he would cut off a plant’s taproot and close to all its fibrous roots to reduce the root ball to fit into a shallow bonsai pot. With some caudiciforms, he would cut the caudex literally in half, and wait for it to develop new roots.

Top growth pruning was equally extensive with the same objective of constraining the plant’s overall growth.

The roomful of avid gardeners of cacti and succulents understood Taylor’s bonsai pruning method, although this approach to gardening was unfamiliar them. These gardeners were familiar with limiting the size of their plants by keeping them in small containers with lean soil mixes and minimal moisture.

At the same time, many were astonished by Taylor’s relatively extreme pruning practices, which freely exceed the usual guideline to remove no more than one-third of a plant’s roots or top growth. While Taylor admitted that some of his early trials of such pruning were unsuccessful, he has found that many plants tolerate this treatment and respond well in time.

The gardeners in attendance learned that the one-third rule for pruning could be overly conservative and that more severe pruning could be effective in limiting plant growth. Bonsai-style pruning of cacti and succulents remains as a specialized form of container gardening and not everyone’s preference we learned that extreme pruning does not necessarily kill a plant.

Taylor’s distinctive pruning practices are closely related to his work in creating containers for plants. Examples of his extraordinary ceramic pots can be viewed on his website,  and his Facebook page, where he is known as “Kitoi” (his childhood nickname).

Even when we know basic gardening methods, new knowledge is always ready for discovery.

Pruning a Fig Tree and Other Plants

Pruning season is upon us. Garden priorities might simply be clearer this year, but the list of pruning tasks has grown dauntingly long.

Cotoneaster berries

Red Clusterberry

One of the most pressing tasks is to shape a Red Clusterberry (Cotoneaster lacteus) that began as a volunteer and grown to dominate one part of the garden. In the past, it has shrugged off significant pruning cuts. A common objective for pruning is to stimulate fruiting, but that is not a priority in this case.

This year’s pruning schedule began with controlling a rampant California wild grape (Vitis californica ‘Roger’s Red’), which had grown without pruning for a couple years, and found its way into the branches of nearby trees and shrubs. Whacking it back has greatly improved its overall shape and should result in a bountiful crop of grapes. I will resolve once again to cover it with netting to protect a fair share of the clusters from unknown midnight marauders.

I have also pruned the new growth on four dwarf apple trees and sprayed them with dormant oil to discourage codling moths. Friends with the California Rare Fruit Growers, noting that moths fly, emphasize the need for neighbors to spray their trees as well, but I see no other apple trees in the neighborhood. I have also planned to cut selected main branches on one apple tree (Malus ‘Cox’s Orange Pippin) to gain some freedom of movement around it. My related resolutions include another spraying one or two more times before bud break, and thinning the fruit when it grows to about the size of a golf ball, to support the development of larger fruit.

My rose pruning project is more than half completed. My approach to hard pruning roses is close to the shearing style described recently in this column. I am also shovel-pruning some under-performing roses and intending to install replacements, with a preference for “own root” roses. Pruning suckers from grafted roses is the downside of whatever benefits might flow from a superior rootstock. Related resolutions: fertilize in the spring and irrigate regularly.

My next pruning focus is a large fig tree (Dorstenia ficus ‘Black Mission’), which dates back to around 1768, was grown in the California missions, and is a very popular fig for home garden cultivation. Fruit tree specialists also recommend several other varieties. Fig trees generally produce two crops of figs each year. The first, called the breba crop, develops in the spring on last year’s growth. The second, the main fig crop, develops on the new growth and ripens in the late summer or fall. My tree has gone several years without pruning, sprawled into large size and produced relatively light crops. Its low harvest might indicate the tree’s age or the effects of drought, but it might simply benefit from pruning. I will prune it heavily during the current dormant period to improve its shape and hope to stimulate a larger main crop.

Here are the basic pruning recommendations.

  • Begins by removing any dead, diseased or otherwise unproductive wood and any sprouts growing from the base of the tree.
  • Then, remove any secondary branches that are growing at a too-narrow angle (less than 45 degrees) from the main branches.
  • Then, cut back the main branches by one-third to one-quarter.

Related resolutions include resuming an earlier plan to establish an espalier form by training branches to posts on either side of the tree, and netting the tree at the appropriate time to protect the ripening fruit from winged wildlife.

My list includes more seasonal pruning tasks, all of which should result in wonderful growth in the spring.

Pruning Roses

The gardening subject with the most advice and the greatest anxiety is pruning roses. January is the right time of the year for this task (with some inevitable exceptions, which we’ll get to), so let’s review.

Close-up of Yellow Rose

Rose ‘Graham Thomas’

Gardeners have good reasons for being uncertainty about pruning roses.

The need for pruning arises from the gardener’s priorities, not the plant’s requirements. This is evident from the existence of wild roses and so-called “cemetery roses” that thrive for generations without the care of any gardener. Pruning and other forms of rose cultivation are intended to produce more blossoms, larger blossoms, more desirable plant forms, and healthier plants.

If all roses were the same, pruning would be a simple matter, but the genus Rosa includes over 360 species, some of which are in cultivation since at least 500 B.C. This botanical diversity complicates the task: several of these species respond better to some pruning practices than to others.

Several species have been hybridized extensively, and thousands of cultivars have been available. The cultivar, however, does not determine the preferred pruning practice; more important determinants include the species and the form.

Roses are generally described in three major classifications: wild (or species) roses, old garden roses, and modern garden roses.

Old garden roses typically bloom once on old growth each season and are cold hardy. They require only minimal pruning, which is done after blooming primarily to manage the overall size and shape of the plants.

For this column, we’ll focus on modern roses, which by most accounts began in 1967.

Modern garden roses are typically hybrids derived from the very old China roses. They are most popular in today’s gardens and characterized as blooming on new growth, and ever-blooming, i.e., they continue blooming throughout the growing season. They are not cold hardy and a hard freeze can kill branches or entire plants. In the Monterey Bay area, cold weather is not a significant threat to these plants.

Pruning these plants begins with removing dead wood, and any branches that are diseased, broken or crossing other branches. These “clean up” actions prepare for cultivation pruning.

Modern garden roses generally benefit from a hard pruning to stimulate the new growth that will produce blooms. This is done during dormancy before new growth begins. In the Monterey Bay area, the best time to prune these plants is in during January and February, so right now is a good time to begin your rose year.

“Hard pruning” has various definitions, with most ranging between one-third to one-half of the canes. One approach calls for removing one-third of the canes entirely, then cutting the remaining canes by one-half.

One intriguing approach to pruning modern garden roses is to simply cut the plant down to eighteen inches in height. Shearing a rose in this way has been claimed to yield the most foliage and blossoms.

The so-called classical approach to rose pruning involves cutting canes to one-third or one-half, cutting at 45-degree angle to an outward-facing bud, opening the center of the plant for optimal light exposure, and removing branches that are thinner than a pencil. This approach yields larger stems, longer stems, and larger blossoms.

Whether you use the classical or shearing approach to hard-pruning your modern garden roses, the important message is to prune them at this time of the year. They will respond beautifully in the spring.

Pruning Evergreen Shrubs

Let’s consider evergreen shrubs, which differ from deciduous shrubs by continuing in leaf year-round. This is not the same as retaining leaves all year: evergreen shrubs sometimes are described as dropping their leaves year-round, for on-going renewal.

A separate group of evergreens is comprised of coniferous trees and shrubs, which are pruned primarily in late winter or early spring, before the appearance of new growth. It is now generally too late in the year for pruning coniferous evergreens. Exceptions include removing unwanted whole branches of spruces and junipers, which may be done at any time, and trimming yews and arborvitae can be done when they have a second flush of growth in mid-summer.

We will address the pruning of conifers next winter. These plants require minimal pruning, except as needed to control their size and shape. If you have such plants in your landscape, mark your calendar with a reminder to consider pruning needs around next February.

The larger group of evergreen shrubs should be pruned as needed in April or May, i.e., in mid-spring, after any risk of frost has passed and ideally before new growth starts. In the Monterey Bay area’s moderate climate, there is little chance of frost except in inland regions, and new growth might appear early in the spring. If the gardener initiates light pruning after new growth can be seen, the downside is that some of the plant’s energy will have been wasted, but the plant will simply replace the shoots that have been trimmed.

For pruning purposes, evergreen shrubs can be regarded in one of three groups.

  • Early flowering. Examples include Berberis, Camellia, Ceanothus, Daphne, Mahonia, Pieris, Azalea, Rhododendron, and Viburnum. They bloom in winter, spring or early summer. Many shrubs in this group should be pruned only lightly and deadheaded.
  • Late flowering. Examples include Eucryphia (Leatherwood), and laurels (e.g., English Laurel). These plants bloom in summer and late autumn on either old or new growth. They need little pruning.
  • Mid-season flowering. Examples include Calluna (Heather), Erica, Lavandula (Lavender), Santolina, and Thymus (Thyme). These bloom on old growth in spring or early summer, or on new growth in late summer and autumn. Generally, pruning involves removing shoots after flowering to about one inch of the previous year’s growth.
Daphne Bloom

Daphne odora ‘Aureomarginata” in bloom

The pruning strategy for these plants follows these following basic steps;

First, remove any diseased, damaged, or dead branches. They will not heal themselves and could spread disease, so prompt removal benefits the healthy parts of the plant and helps the gardener to evaluate other needs for pruning.

The second step, then, is to remove branches that are crowding other branches, or compromising the desired appearance of the shrub. The pruning objectives might include reducing the overall size of the plant, either to work better within the landscape plan or to clear a walkway.

A common problem arises when an established, healthy plant grows larger than expected or wanted. Such outcomes should not be surprising: information on the mature size of a plant is readily available at the garden center or in a reference book or website. A bit of research during plant selection can save future effort.

Shrubs that have become badly overgrown might need rejuvenation pruning. In such cases, remove one-third to one-half of the branches to ground level, and reduce all other branches by one-third. In the following two years, remove half of the older branches to ground level.

Pruning time also should be used as an opportunity to evaluate the overall health of the plant. If it has sparse or leggy growth, consider the need for greater exposure to sunlight. For example, a nearby tree might have grown to shade a plant that grows best in full sun, or the plant might have been installed originally in partial shade. In such cases, prune the tree that blocks the sun, or move the shrub to a sunnier spot.

Another factor limiting the plant’s growth might be poor soil, which can be treated with fertilization during the growth period, and regular applications of compost. The gardener should avoid planting in soil with minimal nutrient value, e.g., sandy soil or sub-soil (lacking loamy top soil). If this is unavoidable, consider planting in better soil in mounds, raised beds, or containers.

A third factor might be insufficient drainage. Some shrubs thrive in soggy soil, but the large majority need oxygen at their roots, so the surrounding soil must be allowed to dry out between irrigations. This can be a problem that results when plants are placed in low-lying areas, or in moisture-retaining clay soil.

The third step in pruning includes mulching and feeding. These actions minimize weeds around the plant and help the plant to grow.

The final step is to stand back to appreciate a job well done.

Pruning Deciduous Shrubs

Right now is the right time to prune some (not all) shrubs in your garden.

The first group of targets for pruning in April included flowering shrubs that bloom in the spring on old wood. These plants should be pruned soon after their blooms have faded. This practice allows ample time for buds to develop and bloom in the following spring. Pruning long after the blooms have faded will remove buds as they develop, and reduce or eliminate blooming next year.

Fading Lilac Bloom

The accompany photo shows fading blooms of a Common Lilac (Syringa vulgaris ‘White Angel’) in my garden. This is one of the Descanso Hybrids, which were developed in southern California for mild winter regions, like the Monterey Bay area. Unlike the lilacs from my youth in Connecticut, these hybrids bloom without a winter chill. This plant bloomed nicely and produced a fine fragrance, and now needs pruning in preparation for next year’s flowering.

Here are examples of additional plants in this group that grow well in the Monterey Bay area.

  • Flowering Quince Chaenomeles speciosa)
  • Forsythia (F. ovata and other species)
  • Japanese Rose (Kerria japonica)
  • Lily-of-the-Valley Shrub (Pieris japonica)
  • Mock Orange (Philadelphus lewisii and other species)
  • Ninebark (Physocarpus opulifolius and other species)
  • Purple-leaf Sand Cherry (Prunus × cistena)
  • Viburnum (V. tinus ‘Compactum’ and other species)
  • Weigela (W. florida and hybrids)
  • Winter Daphne (D. odora)

You can identify additional plants in this group by direct observation. If you are undecided, look up your plant in Sunset’s Western Garden Book, the American Horticultural Society’s A-Z Encyclopedia of Garden Plants, or a pruning reference book. You can also search for the plant on the Internet, ideally by botanical name.

Some gardeners are reluctant to prune their plants, either because of uncertainty or a fear of damaging the plant. It can be helpful to regard pruning as therapy for the plant, i.e., it helps and does not hurt the plant.

Pruning improves the plant first by removing dead, broken or diseased twigs and branches. Such parts of the plant are not good for the plant, and could be harming it by spreading disease or drawing resources.

Other benefits are beneficial primarily for the gardener. Timely pruning will improve flowering, fruiting, and overall shape. Flowering shrubs growing without the care of gardeners or landscapers will develop a pleasing natural habit entirely on their own. They will also produce enough flowers and fruit to reproduce, and enough roots and branches to ensure healthy growth. With this in mind, always prune for specific objectives. Before picking up the clippers, take the time to stand or sit down to examine the plant and decide what pruning is needed.

There are two main approaches to pruning: cut back the plant more or less evenly, and remove selected stems or branches entirely. These approaches can be combined. In this case of the lilac, cut below each faded blossom, just above a developing bud, and also remove entirely up to one third of the older branches to encourage new branches growing from the base.

Net week, we’ll consider seasonal pruning of evergreen shrubs.

Remember to sharpen your clippers to make your cuts clean and easy.

Pruning Roses (and Trees & Shrubs)

It will soon be time for dormant pruning of your trees and shrubs. Pearl Harbor Day (December 7th), which reminds us first of when our gallant sailors and soldiers were attacked in Hawaii, also “triggers” rose pruning season. This day might be early for some, but noted local rose grower Joe Ghio has for years started his pruning on that date. He cultivates a lot of roses, so pruning is not a one-day event, as it might be for your collection. Still, this day reminds us to start pruning our roses, or at least to start thinking about this annual task.

I have written about pruning roses before, and do not want to repeat the guidelines for gardeners who are already experienced pruners. Instead of detailing the process, I will offer some broad suggestions.

First, if you are unsure of your pruning skills, visit the website of the American Rose Society for a refresher. Scroll down to “Pruning Roses” to find eight articles by experts on the subject. You will also see numerous articles on all aspects of the cultivation of roses.

Second, let your roses teach you how to prune. After you have absorbed some basic ideas from the ARS, a book, or some other source, make mental or written notes of how you prune your roses, then monitor their responses over the next growing season. You might even tie ribbons on selected branches to remind yourself of what you did, and to help in watching the plant’s growth.

Third, if you learn best from demonstrations, plan to attend one of the Monterey Bay Rose Society’s free rose pruning classes in January. The Society’s 2017 schedule includes classes at the Alladin Nursery (Watsonville), San Lorenzo Garden Center (Santa Cruz), and the Society’s Display Rose Garden in the Santa Cruz County Fairgrounds (Watsonville). In addition, Joe Ghio might present his popular “Anyone Can Prune a Rose” workshop during the Society’s January meeting in Aptos. For information on times, dates and locations, visit the Society’s website.

McShane’s Nursery (Salinas) also provides free workshops on rose and fruit tree pruning. Visit the Nursery’s website for more information.

***

Fruit tree pruning also can be challenging for backyard gardeners. The dormant pruning season for fruit trees begins when leaves fall and before buds swell, roughly January through March. I recently attended a workshop on pruning fruit trees, conducted by a long-time friend, Peter Quintanilla, who is a UC Master Gardener, an International Society of Arboriculture (ISA) Certified Arborist, and a teacher of Arboriculture and Landscape Pruning at Cabrillo College. Peter spoke at a recent meeting of the Monterey Bay Iris Society (the members of the MBIS are interested in more than irises!).

I will write more on this subject as we near the pruning season, but now is a good time for gardeners to get “up to speed” on this subject. Find good information in your local public library or bookshop or on the Internet. For information on selected trees or shrubs (apple trees for example) try a Google search for “pruning apple trees” to find both article and YouTube demonstrations.

Seasonal pruning of roses and fruit trees will optimize their appearance, health, and productivity. This task, when done in a capable and timely manner, also can be a satisfying exercise for the gardener. If you are unsure of your pruning knowledge, make a New Year’s resolution to master at least the basic techniques. And be sure to let Nature teach you about pruning.

Pruning Tomato Vines

A great many tomatoes are available to home gardeners, either as seeds or seedlings. We are already well into the growing season, so if you enjoy growing tomatoes you are probably already past the stages of selecting a variety or planting seeds or seedlings.

If you are already skilled at pruning your tomato plants, and doing the job in a timely manner, you will not need to read this column.

For the rest of us, let us review the pruning process, with an emphasis on corralling a runaway tomato vine.

The first bit of knowledge about growing tomatoes is that the multitude of cultivars includes just two types: determinate and indeterminate. The determinate plants develop a number of stems, leaves, and flowers, as predetermined by their genetics, and then stop growing. The fruits (actually berries according to the experts) all ripen at the same time, relatively early in the growing season. Pruning of these plants only reduces the harvest.

The indeterminate plants continue to grow and produce stems, leaves, and fruits throughout the season. These are the plants that need controlling.

Expert grower Frank Ferrandino, writing in Kitchen Gardener Magazine, warned, “Left to its own devices, a vigorous indeterminate tomato plant can easily cover a 4- by 4-foot area with as many as ten stems, each 3 to5 feet long. By season’s end, it will be an unsightly, impenetrable, disease-wracked tangle.”

I am growing three tomato plants this year, all of which are the variety, Super Sweet 100, a popular bite-size tomato. I grew one of these plants last year, watched it produce a bounty of very tasty little tomatoes, and develop into the tangle that Frank F. warned about.

Long after I had cleared the bed, a new spring arrived and several seedlings of Super Sweet 100 appeared. I replanted three of the best, determined to control the plant better.

The goals of pruning a tomato plant are to promote larger fruits (not really an issue for cherry tomatoes), keep the plants tidy, and keep the plants off the ground to minimize the potential for disease. The Super Sweet 100 is a disease-resistant variety, but keeping the plant tidy and off the ground still seems worth the effort.

The basic pruning technique is to remove side shoots, called suckers, that grow in the crotch (axil) between the main stem and the side stems. These suckers can produce fruits, but they tend to develop later than the primary fruit-bearing stems and reduce the plant’s vigor.

Tomato plants grow rather quickly, so the removal of suckers is a weekly task. When the suckers are very young, they can be snapped off without the use of tools.

Despite my nest intentions, my plants were soon well on their way to the predicted tangle. This condition inspired an experiment, which took the form of brutally cutting back branches that were sprawling in all directions and in several instances producing little or no fruit.

Super Sweet 100s (green)

More systematic training surely would have been better, but this approach was really the only option at the time. I expect and hope the plants will shrug off my abandonment of best practices and produce another bountiful harvest of sweet, small fruits.

Those fruits are mostly green, still, but have plenty of time to ripen. I’ll try again next year to prune by the book.

 

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Next Year’s Roses

Water your roses during the hot summer to keep them happy and blooming!

A month ago I recommended deadheading re-blooming roses to promote another cycle of blooms. Now, as the end of June approaches is the time to deadhead one-blooming roses, not to extend the season, but to support formation of the greatest number of new buds for the next season.

Roses respond predictably to seasonal attention.

One of my roses that should be deadheaded now is the prolific producer, Rosa mulligani, shown during its recent peak of bloom.

Rosa Mulligani

If my schedule includes deadheading this plant during the next couple weeks, it will provide an even greater cascade of blossoms display next year.

This time of the year is also a good time to contemplate roses in your landscape.

The traditional time for such reflection is late fall and early winter when bare-root roses appear in local garden centers. These are often bleak days for the landscape when avid gardeners hunger for a burst of color in the landscape and respond eagerly to the enticements of dozens of rose photographs.

That’s a good time to add roses to your garden, but not the best time to re-think the role of roses in your landscape.

Many gardens include three or more (perhaps many more!) shrub roses, clustered primarily for ease of maintenance. In other words, there is a rose garden.

The most popular varieties are hybrid tea roses, which cross Rebloomers and tea-scented roses from China, and modern English roses, which cross old roses with hybrid teas. The English roses, notably those by David Austin Roses in western England’s Shropshire County, combine several of the most appealing qualities of roses: hardiness, durability, and fragrance.

The gardener cannot go far wrong by collecting English roses. If you are enjoying your rose garden as it is now, that’s fine.

Still, consider fresh looks at your garden to explore new ideas and your evolving priorities. This approach can inspire creative challenges and new interest in gardening.

Here are a few possibilities.

  • Clustered plants. A popular recommendation is to plant roses in groups of three, to increase visual impact. This approach counters the familiar use of single specimens, which favors variety over garden design.
  • A color-oriented theme. This could be a single color, e.g., white, different shades of a single hue, e.g., pink, or a combination of two or three colors that work well together. A bi-color combination of climbers on a trellis or arch can be striking.
  • Touring rose varieties. Roses have been grown in temperate climates throughout the world for over 5,000 years. A long list of interesting varieties awaits your exploration. Begin an absorbing online research by entering “Wikipedia garden roses.” You could soon be on your way to comparing the common and uncommon varieties in your garden.
  • Combining 0nce-bloomers and re-bloomers. The once-bloomers introduce a different rhythm to the rose season. Some are single-flowered, with just five or seven petals, offering an entirely different look in comparison to the lush varieties with as many as 100 petals. Sometimes, less is more!

We have access to many fascinating varieties within the genus Rosa, even before exploring the ever-expanding universe of hybrids. Your gardening experiences can be enriched by adventuring through the genus.

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

 

Dormant Season Projects

The dormant season does not have an official beginning to mark on a calendar, but depends on a combination of factors, beginning with the individual plant’s biological clock, with which the plant responds to day-lengths.

Another important environmental factor is temperature: lower temperatures trigger dormancy, and higher temperatures can stimulate growth. Climate change has modified the annual cycles and geographic distribution of many plants, and will continue such changes. Phenology is the study of periodic plant and animal life cycle events

Rather than delving into the science of dormancy, let’s consider seasonal projects for the gardener. There are many priorities to schedule over the next few months.

Pruning

As the leaves fall, and the “bones” of your trees and shrubs are exposed, look for ways to improve them through pruning. In general, use sharp tools, begin by removing branches that are broken or diseased, and don’t remove more than one-third of the canopy in one year. As is often true in gardening, there are exceptions: for some shrubs, severe or renewal pruning is appropriate. Extensive pruning of roses, for example, stimulates new growth and abundant blossoms. Several other multi-branched shrubs, e.g., salvias, can be cut to their primary structure or to near the ground before spring growth emerges.

Many gardeners are hesitant about pruning, concerned that they could hurt their plants. Pruning can be done badly so a little time with a pruning book would be instructive. The positive perspective is that pruning improves a plant’s form and stimulates new growth.

pruning fig 1

Pruning during the dormant season

The photo is from the University of California publication, Pruning Small Trees and Shrubs, which is available free online.

A good approach includes observing pruning’s effects during the early spring.

Other Projects

  • Walk through the garden with a critical eye, to spot opportunities for improvement.
  • Transplant or give away plants that have grown too large, or not working in the landscape.
  • Install new plants now, to let the rains irrigate them as they establish roots.
  • Add mulch to cover any bare ground between plants.
  • Plant a cover crop in any fallow planting area.
  • Force a bulbous plant to bloom indoors. Paperwhites (Narcissus papyraceus) are popular, but are so strongly fragrant that restraint can be prudent, i.e., don’t grow a lot.
  • Sharpen your garden tools, or have them sharpened professionally.

Mark your Calendar for the New Year

January 8, 9 & 10 — The 42nd Annual Santa Cruz Fungus Fair, at Loudon Nelson Community Center, Santa Cruz

January 10 — Annual Scion Exchange, Monterey Bay Chapter, California Rare Fruit Growers, at Cabrillo College, Aptos

Late News: Broom versus Leaf Blower Challenge!

The broom versus leaf blower challenge between Ken Foster (on the broom) and Brent Adams (on the leaf blower) will take place Friday December 11th at high noon next to the Westside New Leaf Community Market, at the corner of Fair Avenue and Ingalls Street in Santa Cruz.

Gasoline-powered leaf blowers pollute our environment, disturb our peace, and change our climate. They might be justified for their seeming efficiency, but that too has been questioned. The Broom versus Leaf Blower Challenge, designed as a fair completion, is worth witnessing (sorry about the late announcement). I’ll report the results in next week’s column.