Why Pruning Trees And Shrubs In The Autumn Is Often A Costly Mistake

Gardeners in cold winter climates are usually well aware that the autumn is hardly the ideal season for pruning both evergreen and deciduous trees and shrubs. Is sometimes however, less obvious to gardeners in Mediterranean and other mild winter climates, where frosts if they occur at all, are light and occasional.

Pruning evergreens in cold weather greatly increases the possibility of bacterial and fungal infection, resulting in the development of rot around the pruning cuts. While on the other hand, it is common knowledge, hopefully, that deciduous plants should be pruned in their dormant season, which is of course during the winter.

The trouble in Mediterranean type climates is that the transition from warm summer weather to cold wintry temperatures is often sudden and abrupt. One day at the end of October, it can be 27c in the shade. The shrubs appear too open and leggy, looking as though they need a good prune to encourage dense and compact growth. Pruning the trees and bushes at such a time, can be highly detrimental to their health, because the new juvenile growth will be damaged, inviting infection, if early frosts occur in November. These may be rare, but they do happen.

Concerning deciduous species, the danger of rot that is caused by fungi or bacteria entering through the pruning wounds, is no less acute. It is for this reason, that pruning woody plants should be delayed to the end of winter, so that the young growth, which has been partially simulated by the pruning, will not appear until all danger of frosts has passed for the year. The advice you may read about pruning at the onset of winter, applies to cold winter climates, not to mild ones such as in California, The Middle East, and South West Australia.

A further danger lurking for Mediterranean climate gardeners concerns some trees and shrubs of tropical or sub-tropical origin, that drop their leaves in the winter, but are not naturally deciduous species. These are often more sensitive to cold temperatures than many evergreen plants, like Olive and Viburnum, and are never seen in cold climates. They are however, especially vulnerable to the damage caused by autumn and winter pruning. It is essential therefore, to know what your tree or bush is and where it originates, before assaulting it with the saw and secateurs!

A simple rule, worth remembering, is that evergreen, or cold sensitive trees and shrubs should only be pruned from the spring through the summer. The end of the summer is probably the last chance for a major pruning operation. If the weather is still warm, but winter only a couple of weeks away, then it is best to accept that you have missed the boat and delay the pruning until the following spring.

Mediterranean Gardening Care In the Autumn – A Perfect Time To Feed Your Plants

The tendency for many home gardeners is to think of the spring and summer as the principle feeding seasons for their plants. This may be true in cool, temperate climates, but much less so in Mediterranean and other regions that experience hot, dry summers, and mild wet winters.

In fact, autumn is a secondary growing season in such climates, while during the winter, despite the fact that growth generally slows down, the plants do continue to grow and develop. It is necessary therefore, that in both seasons, adequate supplies of nutrient are available in the plants’ root zone. The question arises then, as to the best method for supplying the essential plant nutrients.

Chemical fertilizer is unquestionably the cheapest and most efficient way of supplying readily available nutrients to the garden plants. The trouble is that the constant adding of mineral salts that chemical fertilizing entails, has serious consequences for the long-term health of the soil. This is liable to express itself in the related problems of increased soil salinity, and the breakdown of the soil’s structure, which leads to a lack of oxygen in the root zone.

In any case, as the plants’ metabolic rate is relatively low at this time, plants require nutrients in small doses, so there is often little need to add chemical amendments such as nitrogen or phosphorous fertilizer. It is at best unnecessary to risk damaging the health of the soil for the sake of hoping to increase, slightly, the rate at which the garden plants grow.

It makes far more sense to adopt a feeding policy that supplies small but steady doses of nutrient, while improving the condition of the soil, which after all is the habitat in which the plants grow. This is where adding organic matter, which can be termed natural fertilizer, comes in. High percentages of organic matter, improves the soil’s structure and thus its aeration, balances its pH in the overly alkaline conditions common in dry climates, and indirectly helps to reduce pest and disease infestations. Paradoxically, the excessive use of chemical fertilizer can raise the soil’s pH (more alkaline) thereby reducing the availability to the plants’ roots, of essential trace elements such as iron and magnesium.

It is important to apply organic matter like compost that has thoroughly broken down to the crumbly, black, odorless state known as humus. With new plantings, particularly in soils that are very infertile, it may be necessary to add some fertilizer, but this can take the form of either organic products or slow-release fertilizer.

There are also environmental issues to consider, as fertilizers leaching out into lakes, rivers, and water tables, are a serious source of pollution. In this regard, commercial compost based on plant waste is preferable to that based on animal manure, although with the latter, the plants will probably benefit in the short term, from the increased concentrations of nitrogen, phosphorous and other nutrients.

Should Plumbago auriculata Be Grown As A Trimmed Hedge Or A Regular Landscaping Shrub?

Plumbago auriculata, or Cape Plumbago, is a somewhat strange landscaping shrub. It has many fine qualities, not least its profuse blooming of sky blue flowers through most of the warm, growing season. For Mediterranean and dry climate gardeners in particular, its capacity to withstand drought, neglect and poor, alkaline soils makes it one of the most useful landscaping shrubs available. Yet it often induces negative reactions from home gardeners. Why is this?

I think the main reason is that it tends to be used incorrectly – as a trimmed hedge by a walkway for instance. As with all plants however, an understanding of its strengths and weaknesses gives one the chance of planting it in situations where it will perform well. Here are a few reasons why Plumbago auriculata is a poor choice for a trimmed hedge, and why it has sometimes earned a bad reputation for itself.

*Firstly, it looks poor at close range. If viewed at a distance, it can create a lovely splash of cool, blue color. Close up though, it tends to appear ragged and messy.

*Secondly, both its flowers and leaves are somewhat sticky, a fact that can turn the bush into a nuisance in narrow spaces.

*The plant is a major litterbug, constantly shedding its sticky leaves and flowers on the pavement, or onto parked cars.

Cape Plumbago is best planted therefore, as a large-scale ground cover, or as a foundation plant, in the more spacious areas of the garden. It grows as a loose, mounding bush to about 2 meters in height (6ft) with almost double the spread. It can be pruned back hard every few years or so, to create a more compact, dense growth habit. Established plants flower beautifully without the addition of chemical fertilizer, although adding compost once a year will always be beneficial.

Growing Requirements

Plumbago can grow in most garden soils, providing there is adequate drainage. It is sensitive to cold and is inappropriate where winter temperatures drop below -2c (28f).Its hardiness to heat and drought, make it ideal for water conserving gardens. In Mediterranean climates, it can get through the summer with virtually no irrigation, but in regions where average highs are over 35c it will benefit from about 100-200mm of extra water a year. It should not be planted in proximity to plants that need regular irrigating, as not only are its water conserving properties wasted, but is a type of shrub that actually flowers better in dry soils!

Viburnum tinus – A Fine Landscaping Bush Not Only For Mediterranean Climate Gardens

Viburnums have long been a popular choice as landscaping shrubs for home gardeners and landscape professionals alike. With their dark green foliage and handsome form, they give the garden a calm, woodsy, refined feel. The dense foliage growing down to the ground makes many species of Viburnum ideal screening plants. They are especially useful as shade hardy plants. There is however, considerable variety amongst the many species and varieties in both their appearance and growing requirements. We will focus here therefore, on one, the Mediterranean native, Laurustinus, known botanically as Viburnum tinus.

This species is hardy to cold down to about -15c, and so is suitable for many climates, not just Mediterranean ones. It grows at a moderate rate to some 3-4 meters (9-12ft) and half as wide. Occasional, light pruning, maintains compact growth and dense foliage. It is better as a screen than as a formally trimmed hedge, as applying the hedge trimmer, bruises and spoils the leaf texture.

Viburnum tinus blooms in the spring with lightly scented white flowers. The flowers are a nice addition to the shrubbery, but not in themselves sufficient reason for growing the plant. The small blue berries though are more visually significant. While they are inedible to us, they attract birds in their droves, which is excellent for effecting a natural pest control, while distracting the birds from the fruit trees in the garden. Laurustinus can therefore be aptly described as decoy plant.

Laurustinus goes well with other landscape bushes of similar foliage texture and growth habit, such as Pittosporum, Feijoa, Myoporum, Raphiolepis, and Coprosma. In frost-free climates, it combines nicely with such shrubs as Duranta erecta, whose fresh, green foliage contrasts interestingly with the Viburnum’s dark leaves, or with the ever-dependable Carissa macropcarpa. It should be noted though, that high humidity is common to mild winter climates, such as coastal regions, a factor that increases the Viburnum’s susceptibility to fungal disease like mildew. It is most successful growing in climates that have dry summers, and cool winters.

Viburnum tinus as a Mediterranean native, can be grown on very little summer irrigation, but will benefit from occasional, deep soakings. This has the positive affect of leaching excessive salts from the soil, to which the species is somewhat sensitive. Its growth can also be stunted by the alkaline conditions typical of many dry climate soils. Adding large amounts of compost and other organic matter to the soil, in addition to its many benefits, lowers the soil’s pH, and thus its alkalinity.

Guava – A Fabulous Fruit Tree For A Small Mediterranean Garden

Guava, in some ways, has to be one of the best fruit trees for a small, private garden. In tropical and sub- tropical climates, it can become quite large and is liable to become a pest. But in Mediterranean and similar hot, dry climates, it is not able to grow outside of cultivation, and only reaches a height of some 4-5 meters. (12ft)

Common or Tropical Guava, Psidium guajava, has many properties that endear it to the home gardener. It has a handsome, sculptural form, which takes to light shaping and pruning; beautiful, reddish, peeling bark; attractive blooms, and of course its tasty and decorative, lemon colored-fruit. Unlike many fruit trees, Guava is hardy to pests and disease, and although requiring water through the hot ,dry summer, can withstand drought if needs be. It is best grown in frost-free areas, and in rich, well-composted soil.

The pear-shaped fruit, have a musky, slightly acidic taste. Eating through the tart skin, you come to the sweet, juicy flesh – a slightly strange sensation. Guava fruit are not to everyone’s taste however. It is this, together with their rather pungent fragrance, that cause people not to include it in their garden, which is a pity considering the overall benefits of the tree. The smell is also a matter of taste. Some people, myself included, love it!

An excellent alternative to common Guava, is Strawberry Guava, Psidium cattleianum. In Mediterranean climates it grows to about 3 meters, (9ft) but can be easily kept smaller. It combines beautifully with other dwarf fruit trees, especially Kumquats, as both the foliage and fruit are similar in size and shape. It follows that Strawberry Guava is a fine choice for a container plant.

The fruit are small, a deep dark red in color, are sweet, and virtually odorless. The bark in mature specimens is even more decorative than the bark of the common Guava, having a reddish, golden brown tint. It is also hardier to cold and can be grown zones that experience light, occasional frosts.

Growing fruit trees in private gardens, often involves battling with a host of pests and diseases, a factor that unfortunately disqualifies the majority of species. As Guavas, at least in dry climates, tend to be virtually pest free, you might well consider including a specimen or two in the garden. You could do a lot worse!

Container Gardening – The Best Way To Feed Your Pot Plants

Container or pot plants, should always be grown in an artificial, soilless medium. One of the consequences of this is that they are dependent on a consistent and reliable feeding regime to a far greater extent than the garden plants growing in regular soil.

The best potting “soils”, or media, available today are those based on perlite, a natural glass that has been excavated and processed to form the white, ultra light product sold in the garden centers. It is used by landscape professionals mainly because of its light weight, an important consideration in roof and balcony gardening, and because it supplies an almost perfect balance between air and moisture. Another property is that it is chemically inert. While this is generally considered an advantage, it does create a total dependency on readily soluble nutrients being available to the plants. The gardener must take this fact into account when choosing which feeding regime to adopt for the container plants.

The use of compost and other organic materials, while essential for the health, aeration, and mineral balance of garden soils, is virtually irrelevant when growing plants in perlite. The name of the game, unpalatable perhaps to organic gardeners, is simply to ensure a ready supply of mineral nutrient, in other words, chemical fertilizer, at all times. How is this best done?

Clearly, hand fertilizing with the highly soluble products such as Ammonium Sulphate or 20-20-20, is highly laborious and time consuming. For while one can fertilize about once a month with the peat-based potting mixtures, plants growing in perlite, by virtue of it being chemically inert, require spoon feeding at least once every two weeks, if not once a week. The majority of home gardeners will tire of such a regime sooner rather than later.

An elegant alternative is to install a fertilizer pump that adds soluble fertilizer at very low concentrations, to the water that is emitted by the drip irrigation system. This method, known as fertigation, is undoubtedly the most convenient, efficient, and successful way of supplying nutrient to pot plants growing in a soilless, inert mixture such as perlite. There are however a few drawbacks that should be noted.

*Many states require the installation of an expensive backflow, prevention device that has to be approved yearly by a qualified person, rather like a road vehicle license. Failure to do so can lead to criminal procedures in some countries.

*In mild winter climates, plants continue to grow and therefore require some feeding during the winter, albeit at a reduced level. This often results in the need to open the irrigation system (the fertilizer is applied via the irrigation system) even when there is no need to do so – an unacceptable waste of water, especially in dry climate gardens.

An alternative to both fertilizer pumps and readily soluble fertilizers is slow, or controlled release fertilizers. These release the essential nutrients over a set period, ranging from two months to one year. They require some labor, as the pellets have to be inserted into the soil, but this only has to be done a couple of times a year.

Container Gardening – Watering Pot And Container Plants For The Best Results

The successful watering of pot plants can be reduced to the aim of maintaining a balance between air and moisture in the potting mixture, so that both are readily available to the plants’ roots. The best way of ensuring this is to water the growing mixture to saturation, while making sure that the excess water drains away as quickly as possible. How, in practical terms is this best achieved?

Firstly, one should water so that the entire surface area of the potting mixture is wetted, and that enough water is applied, so that the excess drains out of the bottom of the pot into a receptacle, or preferably, is carried away by a collecting pipe. Secondly, the next watering should take place when the top 2-3cm (1in) of potting soil has dried out somewhat. Generally, this allows for the desired air/moisture balance.

This method is somewhat counter intuitive, especially as many people confuse it with “over watering”. Over watering, is a situation whereby the soil or potting medium permanently lacks sufficient air. It is generally caused by very frequent but shallow watering, as opposed to the method just described.

Another advantage with less frequent, but deeper irrigation (watering to excess) is that it prevents the buildup of salts in the medium, which is a major, but often overlooked reason for poor results with container plants. Tap and irrigation water are becoming increasingly saline, particularly in dry climates, while dissolved fertilizers (which are mineral salts) add to the salt concentration of the potting soil. Watering to the point that the excess drains out of the pot, periodically leaches out the excess salts.

Which method is best for watering your container plants? Obviously, hand watering with a hose or canister is laborious and time wasting. In outdoor situations, especially in areas with hot, dry summers, where it may be necessary to water at least once a day, hand watering, while feasible for indoor plants, becomes unsustainable. Undoubtedly, installing a drip-irrigation system is the most efficient and effective way of watering the pot plants. Here are some guidelines to help you get the most from the system, bearing in mind that the aim with each watering is to wet the total surface area and the total volume of the growing mixture.

*Space the drippers close enough to each other so that the all the surface area is covered by the water that they emit. A distance of about 20mm (3/4in) is usually enough.

*Be aware of the different flow rates of the drippers. The flow rate is the amount of water emitted per unit of time, expressed in gallons per hour (GPH), or liters per hour. Common metric flow rates are 1, 2, 4, and 8 liters per hour, which is ¼, ½, 1, and 2 gallons per hour.

*Use drippers with low flow rates for shallow and small pots, and drippers with higher flow rates for the bigger and taller containers. The aim is arrive at a total flow rate for each pot that is proportional to its volume, relative to the other pots. So a container that has four times the volume of another container, should have drippers whose total emission, is four times greater per unit of time.

*Turn on the tap, and time how long it takes for the water to emerge. If the drippers have been placed evenly within each pot, and the flow rates are proportional, then water should start coming out of the bottom of the different containers, at almost the same time!

*Set the water timer appropriately, adding perhaps a minute of watering time, in order to leach out the salts.

Container Gardening – Choosing The Right Potting Soil For Optimum Results

The potting “soil” in which container plants grow, is one of the most crucial factors behind the quality of their growth and development. The basic needs of plants are the same whether they grow in garden soil or in pots. But as the conditions created by containers are quite different, the potting soil, more correctly termed the potting medium, has to have different properties from that of ordinary garden soil.

Air and Water

The plants’ root zone has to contain a proper balance between moisture on the one hand and air on the other. Garden soil, especially heavy, clay soil, if used in pots, invariably lacks sufficient air that the roots require for breathing. In such anaerobic conditions, the roots rot, causing the plant as a whole to wither and die.

Alternatively, a potting medium composed entirely of sand, would contain plenty of air in the root zone, but as it dries out so rapidly, would be unable to supply enough moisture for the roots to take up. As sand and soil do not mix well, it follows that an artificial potting medium is an essential precondition for obtaining satisfactory results with container plants. The question is, which type of medium is best?

Today, the various potting media available, attempt to create an optimal balance between air and moisture. Mixtures based on peat and processed substances like vermiculite are most commonly sold in nurseries and garden centers. More recently though, landscape professionals are turning to soilless growing media such as perlite, and because of its special properties, using it almost exclusively in pots and containers. There are a number of reasons for this.

Perlite provides for a virtual optimal balance between air and water. This means that it retains moisture for a reasonable period of time after wetting, but at the same time, contains sufficient air too. It is virtually impossible to over water plants that grow in perlite. It is also extremely light in weight, which is often a vital consideration in roof and balcony gardens. Another important property is the fact that it is chemically inert, which reduces the danger of the medium becoming excessively saline.

Environmental Considerations

Environmentally conscious people have become increasingly concerned about the degeneration of natural bog habitats throughout the world, as a direct result of peat extraction, of which the horticultural industry is a major consumer. Perlite can therefore be preferred on these grounds alone, although its extraction and processing also impacts the environment. Furthermore, being chemically inert, the plants are entirely dependent for their nutrition, on a steady supply of chemical fertilizer, thereby adding indirectly to the pollution of water sources.