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Soil Saturation Can Drown Roots

Only riparian species tolerate sustained saturation.

Irrigation must adapt to weather. It was unnecessary for exposed vegetation during rainy winter weather. It became necessary through drier spring weather. Now, it must adjust for increasingly warm and dry summer weather. This is not as simple as application of more water more frequently. Excessive irrigation causes soil saturation, which damages roots.

Soil saturation is unfortunately common within landscapes that gardeners maintain. The risk of desiccation is more of a concern to gardeners than wasteful irrigation. Desiccation is certainly more apparent than symptoms of saturation. Besides, gardeners assume the costs of neither water nor damaged vegetation. Chronic damage can become significant.

Soil saturation is less common within gardens that lack gardeners, but is not impossible. Soil within pots can become saturated if vigorous roots clog drainage holes. Water which lingers too long in saucers under pots maintains saturation. Irrigation that is too frequent, too generous or both maintains saturation. Of course, different soil types drain differently.

Soil saturation deprives roots of the aeration that they need to survive. A few species are somewhat tolerant of saturation, but fewer tolerate it for long. With few exceptions, newer roots avoid saturation, so disperse shallowly. For trees, this limits stability and increases their likelihood of displacing pavement. Even shrubbery might develop buttressing roots.

Roots that dispersed prior to saturation are vulnerable to rot as soil saturation increases. This not only destabilizes trees, but also compromises their health. Formerly healthy turf grass and ground cover become chlorotic. Some turf grass becomes infested with fungal pathogens, and perhaps moss. Flowers and fruits might shrivel before they develop fully.

It is impossible to prescribe ideal irrigation schedules and application rates for every site. Climate, soil type, slope, exposure and vegetation types are all considerations. Moisture requirements change seasonally and as vegetation matures. Only direct observation can help determine appropriate irrigation frequencies and rates. It is a very involved process.

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Boinkification

Dwarf Alberta spruce needs to know its place.

Many dwarf plants are very practical. The many different dwarf cultivars (cultivated varieties) of false cypress that are grown for their interesting forms, textures and foliar colors are much more proportionate to home gardens than similar specie in the wild, which are big enough to get harvested for timber. Oranges are easier to reach on dwarf trees than on standard trees, which get as big as shade trees.

However, not all plants should be bred to be dwarfs. Dwarf Southern magnolias certainly have their appeal for tight spots, but do not make as much shade as larger trees do. Compact cultivars of crape myrtles (although not actually dwarfs) take too much time to grow above truck traffic to be practical as street trees.

Many classic annuals and perennials are likewise bred to be too compact to be as practical as they were in the past. Annie of Annie’s Annuals in Richmond refers to this all too common practice as ‘boinkification’. It makes many blooming plants more marketable and resilient to shipping and installation, but deprives them of their natural form and elegance.

Short annuals and perennials certainly have their place. Lobelia, sweet alyssum, dwarf marigolds and petunias are fine along walkways and in pots with other larger plants. They also work well as bedding plants for a profusion of color. Yet, there is all too often too much of a good thing. Some flower beds are simply so big and plain, that it would be just as colorful to paint an area orange instead of planting so many marigolds.

Taller flowering annuals like nicotiana (flowering tobacco), cosmos and zinnias add depth behind lower growing annuals. Dahlias are perennials that can accomplish the same thing. Some of the older and less common varieties of familiar bedding plants that have not been so boinkified also work well. There are even petunias that can get two feet tall and wide! These taller plants also provide cut flowers; which is something that boinky plants are not so good at.

Boinkification also compromises fragrance and aroma. Bedding dianthus have almost no fragrance at all; unlike the old fashioned dianthus and carnations that had such distinctive spicy fragrance. Modern zonal geraniums are more colorful than classic varieties, but their foliage is not quite as aromatic.

Not only does increased foliar density of boinky plants promote the proliferation of many diseases and pests; but the genetic violations necessary for boinkification interfere with resistance to diseases and pests!

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Propagation Produces More Garden Plants

Many species propagate reliably by seed.

Seed is the most familiar option for producing new garden plants. Division of perennials, especially overgrown colonies, is another familiar technique. More substantial plants are easier to grow from cutting or layering. Propagation is any process of producing plants. It is how nurseries generate such plants. Some techniques are practical for home gardens.

Propagation by seed is the most practical for most annuals. It is also practical for several perennials and woodier plants. However, not all seed is true to type. Some may become progeny that is different from its parents. After a few generations, ‘Jewel Mix’ nasturtiums revert to orange and yellow bloom. Progeny of most variegated plants lacks variegation.

Propagation by division is more practical for many perennials that form distinct colonies. This includes crowded bulbs. It entails separation of portions of such colonies, or merely single rhizomes. Such portions need only enough root to grow as new plants. Progeny of division are genetically identical to their single parent plant. They therefore do not revert.

Propagation by cutting is the most common technique of propagation among nurseries. It involves cutting pieces of stems and compelling them to grow roots in rooting media. For small scale home garden applications, some of such stem pieces can root in water. Such pieces, or cuttings, are genetically identical to their original parents. They can not revert.

Layering is rather similar to propagation by cutting. Stem pieces remain attached to their original parents during the process though. Burying a portion of stem with its tip exposed stimulates root growth where it is buried. Such stems eventually develop enough roots to sustain themselves after separation. Layering is practical for producing just a few copies.

Propagation is certainly more involved than these brief descriptions imply. It may involve other techniques. Grafting involves assembly of two or more distinct cultivars onto single plants. Rootstock grows from seed, division, cutting or layer. Scions are buds or stems of other cultivars. They graft onto the rootstocks to become the upper portions of the plants.

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Soil Saturation Kills

Use irrigation responsibly.

London plane tree is trendy not because it is all that excellent, but because it is so reliable. It is actually a rather trashy and messy tree that is susceptible to anthracnose and powdery mildew. Landscapers and gardeners like it so much only because the various maples, oaks and other better trees are more sensitive to soil saturation while they get established.

The truth is that most landscapers and gardeners do not want to put any effort into proper watering. While many of us let our lawns die to conserve a bit of water, they waste enough water on lawns and landscapes to sustain rice paddies! This keeps lawns and landscapes superficially green, but eventually causes problems.

Powdery mildew, anthracnose, molds, blights, rots and all sorts of diseases proliferate in damp conditions. Of course, gardeners are happy to apply fungicides and other chemicals to help control diseases; for a price. Also for a price, they are there to replace plants that succumb to any of the many diseases associated with excessive moisture.

Like London plane, several other trees and plants can survive excessive moisture, but only by adapting. If lower soil is regularly saturated, roots are confined to upper soil. This is not a problem for lily-of-the-Nile and many other perennials that can sneak their roots unnoticed into to the upper few inches of soil. However, trees can not get away with this habit for long; since their shallow and buttressing roots eventually expand to displace pavement, other plants and anything else that gets in their way.

Mature and old trees do not adapt. Their deep roots are already set in their ways, so will only rot if they get significantly more water than they are accustomed to. Oaks are particularly susceptible.

Unfortunately, there is no exact formula for determining how much water lawns and gardens should get. There are simply too many variables, such as soil type, drainage, exposure, weather and demand for moisture. Lawns need frequent watering without much volume. Trees prefer more generous watering, but less frequently.

Lawns and trees and everything else in between all need air within the root zone. Watering should therefore not keep soil constantly saturated, but instead allow for adequate drainage and aeration of the soil between watering, without complete desiccation. New plants will of course need more attention until they disperse their roots, but will be happier and healthier with proper watering.

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Street Trees Must Be Adaptable

Pavement necessitates trees with complaisant roots.

Trees of substantial size are not as popular as they had been among old home gardens. Modern landscapes of bigger homes on smaller parcels can not accommodate as many. Clearance from various infrastructure is now more of a concern than shade. Within many modern urban gardens, most available space is in front. Such is the realm of street trees.

This is not because of a lack of obstacles, such as infrastructure that requires clearance. It is more because such obstacles are closer to the ground with more open space above. Many street trees must actually be more adaptable to certain constraints than other trees. Selection of such trees, if allowable by their municipalities, necessitates diligent scrutiny.

Street trees are, most simply, trees between curbs and sidewalks. Some inhabit medians while others are adjacent to curbside sidewalks. Many municipalities prescribe particular trees for particular situations. Anyone who is uncertain of such limitations should inquire. Many municipalities permit property owners to install any trees they prefer, or none at all.

For those who can select street trees, such trees must be appropriate to their application. They must grow high enough to not obstruct sidewalks or roadways. Both sidewalks and roadways require minimal clearances. So do street signs, streetlamps and traffic signals. However, street trees should not grow too large for the confined spaces that they inhabit.

This includes their roots. Aggressive roots of willows, poplars and sweetgum are likely to displace pavement. Oaks, although too big for confined situations, are more docile. Their roots are less likely to displace adjacent infrastructures. Crape myrtle has become overly common because it is too small to cause damage. It does not make much shade, though.

Crape myrtle might also get rather messy, which is another consideration for street trees. It drops flowers during summer, and can get infested with scale, which exude honeydew. Magnolias drop flowers that can be a slipping hazard. Whether deciduous or evergreen, street trees should be reasonably tidy. Over roads, they should not need much attention.

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Home Garden Conifers

Dwarf Alberts spruce is more like a conical shrub than a tree.

Most of the familiar conifers, or ‘cone-bearing’ plants, are large trees like pines, spruces, cedars and cypresses. They are practical trees only with sufficient space, and where their debris and constant evergreen shade will not interfere with lawns or other plants below. Their less familiar compact specie and cultivars (cultivated varieties) that grow as smaller trees or large shrubbery are actually more proportionate, and therefore more useful for refined landscapes.

There are actually several small specie of pine, like Scots, Austrian black, dwarf Swiss stone, mugo, and the various Japanese red, black and white pines. Some of the most compact cultivars grow as dense shrubbery. Others grow as small to mid sized trees with the personalities of larger pines.

There are fewer compact spruce to choose from. Dwarf Alberta spruce, which is a very compact cultivar of white spruce, is perhaps the smallest and most symmetrical, growing as a dense and strictly conical shrub.  Columnar and pendulous cultivars of blue spruce grow in opposite directions, upright and downward, but stay compact enough to be grown as sculptural specimens or shrubbery. There are also pendulous white and Norway spruce.

Several compact cultivars of western red cedar and northern white cedar (Thuja spp.) are popularly grown as tall hedges. They are not actually cedars (Cedrus spp.) and are more often known by the common name of ‘arborvitae’. There are even more Asian arborvitaes (Platycladus spp.) to choose from; many of which have bright golden foliage. ‘Swane’s Golden’ Italian cypress is narrower and denser than the arborvitaes, but not as brightly colored.

Despite the bad reputation of certain cultivars that were planted too extensively decades ago, many junipers are very practical and sculptural coniferous shrubs, as well as ground covers and even small specimen trees. Some ground cover types stay less than a foot deep. Shrubby and small tree types are at their best where they have room to grow without pruning. If ‘Hollywood’ juniper is too old fashioned, the various Rocky Mountain junipers and Eastern red cedar (again, not really a cedar) are worth investigating for their distinctively picturesque forms.

Chamaecyparis are perhaps the most variable of the evergreen coniferous shrubs and trees. Although there are naturally only a few specie which grow into substantial timber trees, there are countless cultivars that are compact enough for residential gardens. Most stay less than thirty feet tall. Many stay less than half as tall. Most have rich deep green foliage; and many have bluish, greyish or golden foliage.

Chamaecyparis are known by a few different but inaccurate common names, including ‘cypress’, ‘false cypress’ and ‘cedar’. (Although the Alaskan cedar is now classified as a cypress, Cupressus or Callitropsis nootkatensis.) Like almost all other conifers, they are best where they can grow naturally without major pruning or shearing to compromise their naturally appealing forms and textures. The most diminutive cultivars are excellent for bonsai and rock gardens, or even in urns of mixed perennials.

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Hummingbirds Enjoy Home Gardens Also

Hummingbirds are very fond of sages.

Floral color communicates to pollinators. Pollination is, after all, the priority of all flowers. Those that rely on pollinators more than breezes for pollination must therefore advertise. They effectively customize their bloom for preferable pollinators. Some incorporate floral fragrance if necessary. Most preferable pollinators are insects. Some are hummingbirds.

Seven species of hummingbird inhabit California. Some are always here. Some migrate south for winter. A few are only here while they migrate between farther south and farther north. All eat only small insects and floral nectar. Blooms which rely on hummingbirds for pollination are happy to provide. They have a mutually beneficial symbiotic relationship.

Many plant species have customized their bloom for pollination by hummingbirds. Many of these flowers are elongated, tubular and curved to fit the long beaks of hummingbirds. Most, although not all, are bright and rich colors that hummingbirds prefer. Bright red and orange are probably their favorite colors. Floral fragrances are more for other pollinators.

Many who enjoy gardening enjoy hummingbirds within their gardens. Hummingbirds are as colorful as some small flowers, but are much more dynamic. They enjoy hummingbird feeders and birdbaths or simple saucers of water. They also appreciate the various sorts of flowers that appeal specifically to them. Such flowers can appeal to everyone anyway.

Hummingbirds enjoy too many flowers to list. Those that customize their blooms for them will be expecting them. Many that customize their blooms for other pollinators can attract them anyway. Zinnia, coneflower and most composite flowers are ideal for pollination by bees. Many of their bright floral colors that attract bees entice hummingbirds incidentally.

Columbine and nasturtium are more customized for hummingbirds. Penstemon, foxglove and various trumpet vines accommodate a range of pollinators. Honeysuckle, lupine and sages do too, but seem to fit thin hummingbird beaks best. Bright floral color of hibiscus, fuchsia, canna and bottlebrush are impossible to ignore. Indiscriminate taste is an asset.

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Flowers Have An Agenda

Flowers are only as colorful or fragrant as they are to attract pollinators.

When the garden is full of bloom, we do not like to think that flowers have an agenda. All their colors and fragrances seem to be displayed merely for our benefit. Who really wants to know that procreation is their real priority; that all their efforts are merely to get pollinated to make seed for the next generation?

Because flowers are not mobile like animals and insects are, they need to rely on wind or pollinators to deliver their pollen to other flowers. Flowers that are more reliant on wind for pollination are not much to look, since they do not need to advertise. The wind needs no incentive to blow. Wind pollinated flowers are instead abundant and productive, to disperse as much of their light pollen as possible.

Flowers that need pollinators need to advertise. They offer all sorts of attractive colors, fragrances, nectar and pollen to attract their particular preferred pollinators. For example, those that exploit the services of hummingbirds appeal to their discriminating taste with sweet nectar in tubular flowers that are mostly in colors that hummingbirds like, orange or red.

All the variety among flowers is designed for the variety of pollinators that they employ. Flowers that rely on nocturnal moths are large and pale, often with infrared patterns (that people do not see) to be visible in moonlight to moths drawn to their sweet fragrance. The offensive fragrances and textures of fly pollinated flowers are delightful to flies. Many flowers appeal to multiple pollinators.

Bees are of course the busiest of pollinators, as they collect nectar and pollen to make honey. They visit any flower they encounter, but prefer those that make abundant and dense pollen that they can carry away. They are very fond of the many different fruit trees; such as apple, pear, apricot, cherry, plum and all their relatives, as well as citrus. They also dig eucalyptus, wild lilac (ceanothus), hebe, firethorn, bottlebrush, honeysuckle and roses.

The difficulty for bees is finding a constant supply of flowers. As apple and pear trees finish blooming, bees want to start visiting other flowers. Bees like a variety of just about any of the annual flowers, particularly pincushion flower, cornflower, snapdragon, foxglove, sunflowers, poppies and lupines. With a good mix, something should always be blooming. Bees are also very fond of catmint, ajuga, thyme, rosemary, penstemon, lavenders and the many salvias and sages.

Those who want to attract bees to the garden should therefore plan for a good mixture of flowers that bees like, so that there is always something to keep the bees happy. Many of their favorite flowers that may not seem very colorful to us use ultraviolet patters that are quite flashy to bees. The choices are not always so obvious.

However, those who do not like bees or are allergic to bee stings, should avoid an abundance of flowers that will attract them. Unfortunately, there are no flowers or plants to repel bees. Also, the coniferous (cone bearing) evergreens and many other wind pollinated plants that are less attractive to bees produce abundant light pollen that is so problematic for allergies.

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Aphid Savor Fresh Spring Growth

Not many hibiscus escape aphid completely.

Dormant pruning last winter did more than concentrate resources for flowers and fruits. It did more than eliminate superfluous growth, which many pathogens overwinter in. It also directed or concentrated resources for stems and foliage. Such growth now grows faster than some types of insect infestation. Aphid, though, are famously prolific and tenacious.

Hybrid tea roses very effectively demonstrate the advantages of dormant pruning. Those that lacked such pruning are more vulnerable to major aphid infestation now. Those that benefit from such pruning are significantly less vulnerable. Even with minor infestations, they may bloom well. Their vigorous stems grow at least as fast as aphid can proliferate.

It is too late for dormant pruning now. Furthermore, this is the beginning of aphid season. It continues until early autumn. Fortunately, aphid are usually not problematic for too long on the same hosts. Their natural predators often find and control them as their infestation culminates. They might continue to be present, but at a tolerable or unnoticeable degree.

Insecticides can be useful for severe infestation, but can interfere with natural processes. Some eliminate predatory insects that can naturally control aphid. If possible, it might be more practical to literally allow nature to take its course. Aphid are prolific, but essentially weak. Mildly soapy water kills them fast without killing many beneficial predatory insects.

Ants symbiotically cultivate aphid in exchange for their honeydew, (which is excrement). They protect their benefactors, and move them to ideal host material. Pruning citrus trees so that they touch nothing else can nearly block access to ants. Application of a barrier to their trunks, such as grease, blocks access more completely. Predatory insects still fly in.

This technique is practical for many small trees, but not low shrubby roses and hibiscus. For them, aphid might be easy to blast off with a spray nozzle on a hose. This procedure neither removes nor kills all aphid, but it can limit their damage. Repetition of the process will likely be needed a few days later, and maybe a few times. Aphid might be persistent, though.

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Shearing Is Not For Everyone

So much lost potential

Back before gardening was cheapened to the degree that it is now, and before most of everything within reach was shorn into submission, many plants were pruned, or not pruned, as necessary to enhance their naturally appealing characteristics. New Zealand flax got planted where it had room to reach out, and only got ‘plucked’ as shoots ventured too far from the center. Lily-of-the-Nile got ‘chopped’ where it crept too far, and ‘thinned’ where it got too crowded to bloom.

Only hedges were shorn; and they were shorn properly, to be slightly narrower on top. Trees actually grew as trees above, and got pruned for clearance below. Vines were selectively groomed, but allowed to climb their trellises. Deciduous fruit trees got the specialized pruning that they require in winter.

Many different kinds of plants that produce generally vertical stems from the base were maintained by a pruning technique known as ‘alternating canes’. This procedure is almost opposite of removing watersprouts or suckers (watersprouts that develop below a graft union) to favor a primary stem. It is actually the removal of primary stems as they get replaced by their own basal watersprouts.

For example, glossy abelia is naturally rather limber with upright growth that spreads outward. Without pruning, it can become an overgrown mounding thicket. However, shearing deprives it of its naturally appealing form, and interferes with bloom. Instead, the technique of alternating canes removes older canes as they begin to deteriorate, allowing new canes to grow more vigorously, arching gracefully outward from the center.

Elderberries and pomegranates may not actually require regular pruning, but are easier to manage if some basal stems are allowed to mature and replace tall and awkward older trunks. The newer growth is more productive (after the first year), easier to reach, and simply looks better. Alternating canes also promotes bloom while preventing thicket growth of mock orange and lilac, particularly since they produce such abundant basal growth.

Heavenly bamboo (Nandina spp.) and real bamboo are two completely different and unrelated plants that both benefit from alternating canes. Heavenly bamboo likes to get its deteriorating or floppy older stems cut to the ground, to allow more space for fresh new foliage to unfurl. Bamboo simply needs old canes cut out as they die.