No One Likes A Sucker

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Citrus have been bred for centuries.

Citrus trees that are grown from seed take a few years to mature enough to produce fruit. As they mature, the juvenile stems are outfitted with thorns that are even nastier than thorns on adult growth! Because most citrus has been extensively bred, seed grown trees are very likely to exhibit genetic variations. This is why citrus trees are cloned from stems of stock trees.

Cloned trees are genetically identical to their parents, so will always produce the same fruit. They are cloned from adult growth, so do not need time to mature from juvenile seedlings. They can therefore bloom and produce fruit as soon as their roots are ready. Also, their thorns are less dangerous.

Cloning citrus is not as simple as rooting them from cuttings though. With few exceptions, citrus trees are grafted onto genetically different rootstock. Most citrus trees in home gardens are grafted onto dwarfing rootstock that limits the size of the trees when mature. Orchard trees are grafted onto rootstock that allows them to get significantly larger.

The graft union, where the upper part of a grafted tree is attached to the rootstock, is typically visible just above the ground. The base of the trunk below the graft union is typically a bit more stout than the relatively lean section of trunk above the graft. Trunks of old trees are often more furrowed below the graft union than above it.

Sometimes, the rootstock tries to do more than provide roots. It can produce stems from below the graft union, known as ‘suckers’ that can potentially compete with the grafted portion of the tree above. Unfortunately, understock grows more aggressively than most types of citrus, so can overwhelm and shade out the desirable parts of an otherwise healthy citrus tree.

The most common understock for citrus produces suckers that are outfitted with unusually big and wicked thorns that are not to be messed with! If fruit develops, it seems to be humongous and disfigured lemons that lack flavor. Before they overtake good citrus trees, suckers should be pruned neatly away as they develop, without leaving any stubble to regenerate more sucker.

Horridculture – High & Mighty

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Camellias are pretty this time of year, but . . .

Camellias have been blooming for a while now. I typically get rather good pictures of them. The pictures are nothing too artistic, of course, and are intended to merely exhibit the floral color and form. A bit of the glossy foliage in the background is nice.

The picture above is not so useful for exhibiting much of the floral characteristics. Even the pink color is muted by the sloppy background and gray sky above. Zooming in would not have corrected the positioning of the flowers. I simply could not get close enough to do any better.

That eave in the lower right corner of the picture is above a two story building. That is where all the blooms of this particular camellia shrub are located. With so much of the lower growth shaded out and gone, this shrub is more like a small tree. The bloom is too high up to be appreciated. The picture below demonstrates what it all looks like without zooming in.

If there were windows facing this big camellia shrub or tree, I would likely prune it only a bit lower, just to keep it below the eave and within view of the windows. Without windows, I know that I really should prune the tall trunks back to what little lower growth remains, in order to promote more growth and bloom closer to ground level where it can be appreciated.

The difficulty I have with pruning it back is that this big camellia shrub or tree is so impressively big and sculptural, and all the glossy foliage looks so good in the foreground of the rich dark brown wall. I do not know what is more important here, the sculptural limbs and rich green foliage that lasts throughout the year, or the colorful but seasonal bloom.

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There is not much to see from this distance.

Frost Is Now Old News

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Minor frost can cause major damage.

Frost was something of a nonissue for some of us this winter. For those of us in milder climates, in rarely is. Those who limit selection of what grows in their gardens to species that are resilient to frost need not be concerned with it. Those of us who enjoy gardening a bit too much are more likely to grow a few marginal species that would prefer to be somewhere with milder winter weather.

Protection from frost might have been a concern prior to the onset of cold weather. Then, there was more concern for the few plants that might have been damaged by frost. Grooming and pruning of damaged foliage and stems needed to be delayed until after the threat of subsequent frost. Now that it is so late in the season, subsequent frost is very unlikely. It is safe to clean up any mess.

Pruning and grooming of foliage and stems that were damaged by frost is delayed for two main reasons. Firstly, the damaged material, although unsightly, helps insulate undamaged foliage and stems below it from subsequent frost. Secondly, premature removal of damaged material stimulates premature development of new foliage and stems that are more sensitive to subsequent frost.

Not only is it now safe to prune and groom frost damaged plants, but such procedures should not be delayed while affected plants recover. The same frost damaged material that provided a bit of protective insulation earlier would now interfere with the healthy development of new stems and foliage. Pruning can now promote new growth that was preferably delayed through colder weather.

Because the weather has been so pleasantly mild for quite a while already, new growth may already be developing among some frost damaged plants. Damaged material should be removed as carefully as possible to limit damage to such new growth. Many perennials that were not damaged this year might be pruned as if they were, to remove tired old growth, and promote new growth.

Many of the dormant spores of fungal and bacterial pathogens that overwinter in old foliage will be removed as such foliage gets groomed away.

Seasonal Pruning Is Precisely That

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Some trees get pruned after bloom.

Seasonal pruning is just as the terminology implies, seasonal. It might seem as if it all happens in winter. Most of it begins after cooling autumn weather initiates dormancy. Most of it is completed before warming spring weather stimulates vascular activity and resumption of growth. That is why most seasonal pruning is referred to simply as winter pruning. Winter really is best for most of it.

However, most is not all. Plants that are damaged by frost should not be pruned immediately. Because pruning removes insulating vegetation, and stimulates new growth that is more sensitive to frost, such pruning is delayed until after the threat of subsequent frost. Birches and perhaps maples are popularly pruned in late summer or autumn because they bleed so much if pruned in winter.

Flowering cherry, plum, peach, crabapple and quince do not need the same sort of pruning that their fruiting counterparts rely on. Their exquisite bloom is the priority, rather than fruit. Pruning prior to bloom could diminish their potential. They can instead be pruned immediately after bloom, as new growth is emerging, or later in summer after soft new growth has become a bit more resilient.

Lilac and forsythia should likewise be pruned after spring bloom, but more aggressively than the flowering fruitless ‘fruit’ trees. If not pruned enough, they will produce fewer canes through summer to bloom the following spring. Older and gnarlier canes should be cut to the ground to favor younger and less branched canes. Old Oregon grape and Heavenly bamboo canes can be culled too.

Redtwig dogwood and cultivars of willow that are pollarded or coppiced for their colorful twigs can be pruned later too. There is no need to deprive them of their primary assets prematurely. They should be pruned as winter ends though, before their buds start to pop. Pussy willow is an exception that gets harvested after buds have fuzzily popped, but before new growth begins to develop.

Evergreen plants can be pruned late in winter, just before new growth develops to replace what gets pruned away.

Deciduous Fruit Trees Need Pruning

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Dormant fruit trees will bloom soon.

Deciduous fruit trees have no business in a low maintenance landscape. They need as much specialized pruning while dormant in winter as roses need, and on a much larger scale. Neglected trees get disfigured by the weight of their own fruit. Disease proliferates in their thicket growth that develops without pruning. Overgrown trees produce most of their fruit where no one can easily reach it. Fruit that can not be harvested attracts rodents.

Of course, deciduous fruit trees are certainly worth growing if they get the specialized pruning that they need. Pruning concentrates resources so fewer but better fruits develop. Fruit bearing stems are better structured to support the weight of their fruit, and lower so that the fruit is easier to reach. Pruning also promotes more vigorous growth, which is less susceptible to disease and insects.

Now that it is February, and the weather has been unusually warm, deciduous fruit trees that have not yet been pruned will need to be pruned very soon. They will be sensitive to such major pruning once they start to bloom. The pruning is too specialized to explain here in just a few sentences. Fortunately, Sunset publishes an very detailed book about “Fruit Tree Pruning” that explains how to prune each of the different fruit trees. Pruning will be more extensive each year as trees grow, but also becomes more familiar.

Stone fruits like apricots, plums, prunes, nectarines and peaches (that have hard seeds known as stones), need the most severe pruning. Their fruit develops on stems that grew last year. These stems should get cut short enough to support the weight of the fruit expected to develop next year. The ‘four Ds’, which are dead, dying, damaged and diseased stems, should get pruned out as well. Cherries and almonds do not get pruned as much because their fruit is so lightweight; and out-of-reach almonds simply get shaken down anyway.

Apples and pears are pomme fruits that need similar pruning, but also produce on stunted ‘spur’ stems that should not be pruned away. Spurs may continue to be productive for many years. Figs, persimmons, pomegranates, mulberries and grapevines all need their own specialized styles of pruning.

Pollarding And Coppicing Appall Arborists

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Pollarding is disturbingly severe but effective.

Very few arborists in America condone the extreme pruning techniques known as pollarding and coppicing. Both techniques essentially ruin trees, and deprive them of their natural form. Affected trees likely require such procedures to be repeated every few years or annually. Otherwise, they are likely to succumb to resulting structural deficiency. Restoration of such trees is rarely practical.

Pollarding is severe pruning to remove all except the main trunk and a few or perhaps several main limbs. Coppicing is even more severe, and leaves only a stump. Both are done while subjects are dormant through winter. Most or all new growth that develops is spring is concentrated around pruning wounds of the previous winter. Some coppiced stumps generate growth from the roots.

If pollarded or coppiced annually, all growth that developed during the previous season gets pruned cleanly away to where it grew from since the previous procedure. Distended ‘knuckles’ develop at the ends of pollarded limbs or coppiced stumps as the pruning is repeated for a few years. ‘English’ pollarding leaves a well oriented stub of any desired length to slowly elongate each knuckle.

Pruning wounds should be as flush to each knuckle as possible, without intrusive stubble. The many small pruning wounds left on each distended knuckle will compartmentalize (heal) efficiently as new growth develops during the following season. Pruning below a knuckle might seem to be more practical, but leaves a single but big wound that could decay before it gets compartmentalized.

Delaying pruning for a few years creates bigger wounds, and allows innately structurally compromised stems to get heavy.

Pollarding and coppicing were developed a long time ago to produce kindling, fence stakes, cane for basketry, and fodder for livestock, as well as silkworms. Nowadays, it is done to contain big trees, enhance the size and color of leaves, produce juvenile foliage, produce colorful twiggy growth, or prevent unwanted bloom or fruit. Not many trees are conducive to such severe techniques.

Pollarding Is Extreme Tree Pruning

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Pollarded knuckles look like science fiction.

Most arborists insist that pollarding is horticulturally incorrect. However, most of us who pollard trees in our home gardens are not arborists. Pollarding is technically detrimentally disfiguring to trees. However, some trees that are naturally short lived can live much longer if pollarded properly. That is the trick; doing it properly. Pollarding is certainly a distinctive pruning style that is not for everyone, but can be both practical and sustainable in certain situations.

Pollarding is an extreme pruning technique that involves the removal of all or almost all of the stems that grew since the last time the technique was done. The new growth gets cut back cleanly to distended ‘knuckles’ that develop at the ends of the original stems. Traditionally, one or two strategically aimed stubs from the removed new growth are left on each knuckle to form a new knuckle a bit beyond knuckles of the previous year. Locally though, stubs are typically omitted.

New growth must get cut back cleanly so that the wounds can get compartmentalized (healed over) as efficiently as possibly. Stubs interfere with this process. If one or two stubs are left on knuckles to form new knuckles, they should be long enough to get some distance from the original stubs, but short enough to not be too awkward. Knuckles should not get cut off! Such large wounds do not compartmentalize fast enough to avoid rotting.

Pollarding can only be done in winter, both because plants are dormant, and also because the weather is not so dangerous. New growth starts to shade exposed bark before it gets scalded by intensifying sunlight and heat in summer. Once they come out of dormancy, plants would be seriously distressed by such severe pruning. Because new growth is so vigorous after pollarding, it can become sloppy if pollarded less than annually. Some plants that grow slowly or produce stout stems may get pollarded less frequently.

London plane (sycamore) and fruitless mulberry are the most commonly pollarded trees. Silver maple, silk tree and various elms, willows and poplars adapt well to pollarding as well. Locust and purple leaf plum can be pollarded, but will be deprived of bloom. Bottlebrush can bloom later in the same year after getting pollarded, and probably will not need annual pollarding anyway. Pollarded bay trees can be kept small, and will provide better herbal foliage. Certain eucalyptus can be kept juvenile if their juvenile foliage is more appealing than their adult foliage.

Figs Are Easy To Propagate

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Some grasses can propagate by division.

The easiest way to propagate new fig trees may seem to be violent, but it works. Basal shoots that grew last year from the roots near the trunks of ungrafted trees can simply be torn out of the ground with as many attached roots as possible. These shoots can then be planted directly wherever new trees are desired, and watered in. Larger shoots may need to be dug out, and might do better if pruned down to just a foot or two tall when planted. Smaller shoots can be potted to grow through next summer, and then get planted in the ground next winter.

Tearing the shoots off in this unpleasant manner is effective for two reasons. It gets the most roots for the shoots to help the grow into new trees. It also removes more of the burl growth that produces the shoots than simply cutting the shoots neatly. Even if copies of the original tree are not desired, the basal shoots must be removed anyway. Simply pruning them away leaves more burl growth so that more shoots grow back next summer. Ideally, well maintained trees should actually not produce basal shoots.

Fig trees are innately easy to grow from basal shoots or cuttings while dormant through winter. Basal shoots, even those that get pulled without any obvious roots, will develop roots more efficiently than stem cuttings that were never in contact with the soil. However, if no basal shoots are available, stem cutting work just fine. Furthermore, grafted trees (which are quite rare) can only be copied by cuttings from above the graft. Basal shoots from below the graft will only produce copies of the understock.

Just as unwanted basal shoots and cuttings from pruning scraps can be grown into fig trees, overgrown perennials in need of thinning can be divided to propagate more of the same. Lily of the Nile, red hot poker, daylily, mondo grass, African iris, terrestrial yuccas, some ferns and some grasses are not only easy to propagate by division through winter, but many perform better if divided every few years or so, before they get too crowded. The common giant yucca develops big trunks instead of clumping shoots, but can be propagated just as easily from big cuttings.

Fruit Trees Need Specialized Pruning

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Even almond trees need some pruning.

For centuries, fruit trees have been bred to produce unnaturally abundant and unnaturally big fruit. That has worked out well for those who enjoy the resulting fruit. It is not such an advantage for the exploited trees that must produce it. Without specialized pruning, most of such trees are unable to sustain healthy development of all the fruit they could potentially produce, or support the weight.

Specialized pruning concentrates resources into less excessive fruit of superior quality. It improves structural integrity of limbs that support the weight of all the fruit too. Trees that produce smaller and lighter fruit, such as cherries, may only need to be trimmed occasionally to eliminate structurally deficient growth. Heavier fruit, such as peaches, necessitates much more aggressive pruning.

Almost all deciduous fruit trees should be pruned about now, before they bloom and foliate at the end of winter. Such pruning is too severe to be done while the trees are active in spring. Summer pruning to maximize production within less space is the only practical option to dormant pruning. Evergreen fruit trees, such as citrus and avocado, should not be pruned or groomed during winter.

The main group of deciduous fruit trees that require dormant pruning in winter are stone fruit, of the genus Prunus. This includes peach, nectarine, apricot, plum, prune, cherry, various hybrids and almond. The second main group are pomme fruit, such as apple, pear and quince. Fig, persimmon and grapevines, as well as roses, need specialized and perhaps very aggressive pruning too.

Dormant pruning of deciduous fruit trees, roses and grapevines is too complex to describe adequately here in just a few paragraphs. Nonetheless, those who grow such plants must be aware of how important it is, and ideally, know how to do it. Nowadays, it is nearly impossible to procure services of horticultural professionals who know or care how to execute such procedures properly.

They Don’t Know When To Quit

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The good news is that these billowy white blooms were not wasted.

The main difficulty with such a mild climate is that many plants do not get sufficient chill in winter. Several types of apples do not perform well here without it. Only a few are productive in Beverly Hills (in the Los Angeles region), where I sometimes need to modify my gardening column accordingly. A few of my neighbors here somehow grow peonies; but I do not even bother.

Even plant that require more chill than they get here seem to be aware that it is cooler at this time of year. Their deciduous foliage turns color and eventually falls to the ground. They just want the weather to get a bit cooler and to stay cooler for a bit longer before they are convinced that it is really winter. Otherwise, they think that autumn simply merges directly into spring.

I really do not know what hydrangeas are thinking though. They perform about as well in milder climates of Southern California, and may not bother to defoliate completely if old foliage can linger until it is replaced by new foliage. In the mildest climates, bloom is merely subdued through winter, but might continue sporadically. I am not convinced that they need any chill at all.

The hydrangeas here get pruned shortly after the roses, and almost as severely. (They are a bit more complicated than roses, and a bit less cooperative, but respond well to their pruning.) I started the process on Thursday with a few that needed to be relocated, and will be finishing on Wednesday or Thursday. Most of the remaining yellowed old foliage falls away in the process.

Their lingering bloom is a bit more disconcerting. I hate to waste what the old hydrangeas put so much effort into producing. Some of the best blooms were outfitted with a bit of eucalyptus foliage (since they lacked their own) and given away to others who work here. However, there were invariably some undeveloped blooms that were just discarded as they got pruned away.

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Undeveloped bloom was merely discarded with the rest of the debris.

Hydrangeas seem to appreciate a good chill, but do not seem to need it, or expect it to last for very long. I sometimes wonder if I could just groom them to remove old canes throughout the year rather than pruning them aggressively in winter. I do not remember ever pruning any in Southern California, but might expect them to be less responsive to the even milder weather.

For me, they would be easier to prune where winter is cool enough for them to be completely dormant. Without foliage, it would not seem like I would be pruning them while they are still active. Without bloom, I would not be concerned about the waste. I could just prune them like so many other deciduous plants. There really are a few disadvantages to mild winter weather.

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Hydrangeas that were transplanted got pruned and dug bare root.