Tropical and Sub tropical Plants can be grown in temperate climates; but they need to be kept away from the extreme cold. There are many ways this might be done, depending upon how cold it gets, and how sensitive the particular plants are. Many people grow the plants indoors. Some use a greenhouse or shade house. Some simply find ways of protecting them for those periods of time when the temperature drops too low.
GREENHOUSES & SHADEHOUSES
Even if you live outside of the tropics, you can grow tropical plants with the aid of structures that alter plant growing conditions. Greenhouses, shadehouses, pergolas and conservatories are all useful structures for providing protection from weather extremes for tender plants. Such structures are commonly used to grow plants from the tropics and sub-tropics in cooler climate areas, or in areas where there is insufficient shade (e.g. growing rainforest understorey plants without the protection of upper storey plants).
For convenience in a cold climate, nothing beats a conservatory - a glasshouse attached to the house, on the north or east side. A conservatory or greenhouses will allow you to:-
Propagate new plants
Grow tropical plants in cooler climates
Protect plants which are cold or frost sensitive over winter
Protect plants from wind, hail and pests
Grow vegetables, cut flowers or berry fruits out of season, or faster than might be achieved outside.
This is great if you don't feel like walking to a greenhouse at the bottom of the garden in the rain. Conservatories are popular in colder climates like Europe, because even if it is cold and windy outside, as long as the sun is shining, it is pleasant to sit in a warm conservatory and dream of tropical islands. However, conservatories can be expensive to construct and a bay window or even a sunny window sill can be used to grow some parsley or other herbs. Conservatories can be covered with blinds or shadecloth in summer, (or grow beans on a trellis just in front of it) and in winter kept open to the house to warm it up.
GREENHOUSES
Greenhouses or glasshouses provide permanent protected growing areas, and are usually sited independently of other buildings. When planning a greenhouse consider the following:
* Site
Is the site on a slope or flat. Too steep a site will make it impossible to build the greenhouse unless it is stepped.
Is the site in sun or shade. A natural windbreak will also be useful, but take care to avoid shading the greenhouse.
Does the greenhouse require a concrete base?
What sort of soil is the greenhouse going to be built on. A sandy soil will give good drainage from any watering, but a clay soil will not. You may need to install a drainage system before construction.
If you decide to build a greenhouse at the bottom of the garden it is a good idea to at least partially obscure it with climbers on a trellis, or behind some shrubs. A greenhouse can tend to dominate, and ruin an otherwise carefully designed garden. Care should be taken with your choice of screen, as a heavily shaded glasshouse will not be suitable for growing plants.
* Cost
How much are you prepared to spend? The cost will vary depending upon materials, design and location.
* Orientation
Which way should the greenhouse be sited, either north - south or east west? A greenhouse that is sited with it's ridge running east to west is best, but this may be a fact which is governed by the space that you have available.
* Water Supply
All of your plants will need watering and you do not want to be carting huge amounts of water over long distances to the glasshouse. A water supply within the greenhouse would be ideal.
* Electrical Power
If you are planning to automate some of the functions of your greenhouse, or provide electrical heating, a power supply will be essential. A greenhouse will be a damp place, so it is important that all electrical connections are made by a registered electrician.
* Future expansion
Although your new greenhouse may seem vast when it is first erected, you may find that in a few years time you need to expand it. So a design that allows for expansion may well prove useful.
Framing Materials
* Metal
Aluminium frames are popular because they resist rusting. Galvanised iron or steel are also used, though over time corrosion can become a problem. Glass works well with metal, however PVC film and other plastics can deteriorate if in direct contact with metal (e.g: metal will get very hot in summer sections of PVC film touching it will crack or tear much sooner than parts not in contact).
* Timber
Timber does not heat up like metal, however it will rot, particularly in the humid environment of a greenhouse. Some treated timbers will last for many years, but it is important to check that the materials used in treating the wood are non-toxic to plants. Pests such as mealy bug may also breed in timber.
Covering materials.
Greenhouses are commonly covered with glass, polythene or polyflute. Other alternatives include polycarbonate sheeting, fibreglass and others. All have advantages and disadvantages:
Glass - very long lasting, strong, expensive. Excellent light transmission and holds heat in well. Looks good.
Polyflute, corflute - medium life span, quite strong, moderately expensive. Poor light transmission, good insulation. Tends to collect dust. Easy to build with.
Polycarbonate - Long lasting, very strong, expensive. Available in clear or smoky grey sheets, corrugated or 'Grecca' style. Excellent light transmission, flexible and easy to work with. Collects dust. Looks good.
Fibreglass - tends to collect dust, and become brittle and yellow with age, generally not as good as alternatives. Green corrugated sheets are no good for growing plants under.
Polythene - short life span, changed every three to five years in most cases. Relatively cheap in the short term. Inclined to form condensation on the inside which causes dripping (on plants and you), and leads to heat loss. Not as well insulated as glass, occasionally used as a double cover to improve insulation, but some light is lost. Good light transmission but some brands become yellow with age. Strength and durability and brittleness depends on brand, with some incorporating woven thread for strength. Can flap noisily in the wind and is not particularly good to look at. Polyhouses are better sealed than glasshouses and tend to get hotter than glasshouses, and more humid, which makes them less comfortable for some plants and people.
What to Grow in Conservatories and Greenhouses?
This is of course largely a matter of personal preference and the range of plants that you can grow will be only controlled by the limitations of your conservatory or greenhouse. Temperature will be a deciding factor as to the choice of your plants, and you need to decide on what temperature you are going to have as a constant in the greenhouse.
* Temperature control
If you want to control the temperature in your building, you can do this in a number of ways.
The sun will warm the structure during the day, and the degree of warming will depend upon the time of the year, time of day and weather conditions that day.
Heaters can be used to add to the heat in the house. The heater must have the ability to replace heat at the same rate at which it is being lost to the outside.
Vents and doors can be opened to let cool air into the house, or closed to stop warm air from escaping.
Shade cloth can be drawn over the house to stop the warm sun penetrating it. Whitewash can also be applied to the glass to give the same effect. The whitewash used is usually one that lasts the summer but will wash off with weathering to allow the penetration of warming light in the winter.
Fans can be used to lower temperature.
Watering or mist systems will also lower temperature.
*Benching
If you intend to grow pot plants in a greenhouse, you probably need some benches. Benches enable you to raise plants off of the greenhouse floor, keeping them away from disease and often in better light. A tiered system of benches usually provides more useable space than if you were to only use the floor. Benches can be made out of metal, wood or plastic, and are usually either slatted or solid in construction. The surface of a bench should drain freely. Wooden benches if not treated with preservative can rot, and may become infested with pests such as ants or mealy bug. Capillary matting (ie. a continually moist, absorbent material, sold by some greenhouse companies) will help reduce the need for watering if used on a bench, to sit pots on.
PERGOLAS
Pergolas are structures built to provide shade and shelter. They can produce a cool humid environment preferred by ferns and many tropical tree seedlings; or can be covered with water proof material to prevent rainfall thereby reducing humidity, increasing heat and producing a more arid situation.
Pergolas usually consist of a roof supported by posts and/or walls of an adjacent building, with the sides open or enclosed. The roof is commonly made from beams covered by something to filter the sunlight while still allowing rain to penetrate. Pergolas are commonly constructed over a path, patio or verandah so as to increase the useable area of the land for living space or plant growing. They may be attached to or between buildings. In the southern hemisphere, pergolas are normally attached to the north side of the house to provide shade in the heat of the day. In warmer climates a pergola can also be very useful on the east and west sides of your house where the morning and afternoon sun can be more of a problem than the high midday sun.
There are three parts to a pergola:
The posts (uprights)
Roofing framework
Covering material (not always used).
Posts and roofing framework
These are usually made from timber. Metal is sometimes used. In most situations, a height of 2.5 metres is ideal for pergolas.
Covering Materials
The covering material is very important as it will effect the amount of light, or shade, that the plants will receive. A solid cover creates a more shaded, cooler area, but restricts rainwater moving through. Plants under a pergola may need more watering.
The main choices in coverings are:
a. Growing Plants
* The combination of foliage, flower, scent and colour provide a sense of continual change and freshness.
* Regular pruning may be necessary to remove growth hanging too low, or spreading beyond the pergola.
* Avoid plants that may damage an attached building (eg. Ivy) or block guttering.
* Deciduous climbers will let light through during winter (when bare of leaves), but provide coolness and shade in summer.
b. Brush (cut foliage for plants)
* Brush can be purchased in bundles or slabs, or cut yourself (do not cut it from the bushthough) from plants like Melaleuca and tea tree.
* It can in some cases carry disease and may be readily flammable if lit.
* Soft wooded plants are rarely any good as brush.
* Water moves in an irregular way through brush, creating heavy dripping in some places.
c. Shadecloth
* Shade cloth comes in a variety of degrees of shade.
* Lasts for a very long time.
* Needs to be well supported by beams and slats, or it will sag, forming low spots which collect leaves and other rubbish.
d. Timber slats
* Timber slats or battens give an optimum cooling effect if run in a north-south direction.
* All timber needs to be treated to extend life. eg. PVC or Fibreglass sheet
* Sheeting must have a slope to move rainwater. It is normal to slope the roof away from buildings or pathways, to keep those areas free of water.
* A collection system or guttering may be used at the bottom of the roof, and take it to a drain.
SHADEHOUSES
The covering material of shadehouses has been primarily with the use of wooden slats or shade cloth. Colours are now available in:
Green - although it may look good in the garden, it is the least desirable colour as the plants do not photosynthesis effectively under this colour cloth.
Black - very popular and is perhaps the colour which is least noticeable.
Brown - fits in well with rustic and colonial style homes and with native bush gardens.
Sandstone - may be in keeping with the colour of the bricks or roof tiles of a house.
Pale blue and white - go well with white houses and swimming pools. White shade cloth is good for growing plants, as they are protected but still grow in bright conditions, as the light is reflected and dispersed as it passes through.
In warmer climates, darker coloured shade cloth will have more of a cooling affect than the lighter colours.
Shade cloth is available in a range of shade strengths, ie. 50% and 70%. Stronger cloth is better in warm hot areas for the growing of more tender plants. 50% shade cloth is good for most other plants especially orchids and other flowering plants.
Shade cloth can also be used as a windbreak substance.
Pergolas and shade houses are ideal for growing ferns, azaleas and orchids. They can also be used to grow rainforest plants.
GARDENING FOR BALCONIES, COURTYARDS, ETC...
Those plant enthusiasts that are situated in a temperate climate have other options open to them besides the greenhouse. Many areas around the house may be suitable for growing tropical or warm climate plants because a warm micro climate is created. Courtyards, especially, paved or concreted areas tend to have much higher temperatures than other parts of the garden. Balconies too, can often experience a slightly higher temperature, particularly if they are well protected ones.
With a little imagination, research and planning a courtyard or balcony can become the most striking part of your home, drawing your attention from the interior of the house, and creating a feeling of extra space or of the exotic. Landscaping a courtyard or balcony is like landscaping any other type of garden; in that planning is the key.
THE COURTYARD/BALCONY ENVIRONMENT
Often courtyards and balconies are exposed places, if not to wind then to sun which can be inhospitable to many types of plants. Wind in particular may be a problem, and depending on the aspect, a balcony may be either a sun trap, becoming too hot at times; or continually in the shade, starved of light and warmth particularly in winter. Balconies may be protected by large trees growing nearby, or shaded by adjacent tall buildings. Large structures may also create wind tunnels though, complicating the task of successful gardening.
LANDSCAPING A COURTYARD OR BALCONY
-Consider possible uses for the area to be landscaped.
Your selection will depend on the amount of space available, and it's outlook. It might be for sunbaking, for outdoor living, for outdoor entertaining, for eating outside, for growing cut flowers, herbs or vegetables to use inside, for aesthetics (to make the building look good from outside, or to provide a feature to look at from inside.
-The walls of the building backing the area.
Consider the style of the wall, if it's attractive - then landscape to complement it and show it off; if it's unattractive - then landscape to hide the walls, or do something, such as painting to improve the appearance of the wall.
-Are there side walls?
These will help to further "contain" the area. This can have a variety of effects, such as blocking off neighbouring units, restricting good views or blocking out bad ones, reducing the overall feeling of extra space that more open verandahs provide, reducing wind (which can be both beneficial, making the area more pleasant, or can reduce the cooling effect that the wind provides on hot days).
-What type of windows or doors lead or look out onto the courtyard or balcony?
Remember the view from inside. It is important to avoid placing objects, such as outdoor furniture, B-B-Q's, or plant containers where they will create obstructions or reduce access.
-Surfaces might be dressed up by paving, or by painting to create different effects.
-Getting more use of available space.
Look at existing structures that are currently within the area to be landscaped. Are they essential? Are they aesthetically in tune with what you desire in a landscaped arrangement? If not remove them, at the very least you might try to hide them.
HOW TO GROW PLANTS ON BALCONIES
There are three main problems with growing plants in these ways on balconies: They often dry out easily. They run out of nutrients. Growing space is limited.
Drying out
Plants are normally grown in some type of container on a balcony. If the area is exposed to wind, or excessive heat, it is important to avoid the roots drying out. There are a few things you can do to minimise this:
-Grow in larger containers (eg. Big pots or large planter boxes with a deep soil (at least 50cm/ 20in deep).
-Provide a constant supply of water by either using a capillary watering system (eg. water well pots), a drip irrigation system, or a hydroponic system. Watering of your plants will be much easier if there is access on the balcony to a tap, or a water pipe that can be accessed in some way. Watering may still be required every day.
-Mulch plants heavily.
-Use drought resistant plants.
-Build a wind break (e.g. erect a wall of shade cloth across one end of the balcony.
-Use a good quality potting soil.
-Add things to potting mix to improve their ability to hold soil (eg. peat moss, vermiculite, perlite or water crystals). NB: Improper use of these materials can create more problems, so get advice from an expert before using them.
Nutrition
Regular feeding is important! Nutrients will be lost from soil both through leaching away in drainage water and through plants extracting nutrients from soil. Frequent light applications of nutrients is preferable. Heat and frequent watering can cause a greater leaching of fertilizer through the bottom of pots than what might otherwise be the case. Recent research has shown it is not uncommon for up to 90% of fertiliser applied to container grown plants by some nurserymen to be wasted! Slow release fertilisers are best in most cases. Cover the fertiliser with mulch or potting mix, so that direct heating from the sun doesn't cause chemicals to be released too fast.
It is also important to note that plants grown in warmer sites will have a longer growing period and therefore may require more fertiliser and moisture over the growing season.
HOT DRY AREAS
Water is the most important commodity in an area which is dry. Rain is infrequent, although it may be torrential when it does occur and will be responsible for flash flooding followed by great bursts of greenery and growth which soon wilts once the excess moisture has evaporated. The problem posed for the dry climate gardener is how to conserve this excess water and make the most efficient use of it until the next rains occur.
The watering requirements of your plants can be minimised in the following ways:
* By choosing plant species and varieties that best suit the local climate.
* By maintaining a well balanced fertile soil (appropriate to the plants selected).
* By watering in the cool of the day.
* By using micro-irrigation systems e.g. trickle systems where possible.
These are much more efficient in their use of water.
* By slow thorough watering. A thorough deep watering once or twice a week will be more effective than light waterings every day or two.
* By avoiding spraying water on windy days.
* By considering soil type when selecting a watering system.
Clay soils hold water well and will distribute it horizontally, so a drip system is suitable. Water runs quickly through sandy soil and a micro spray, which distributes water over a broader area than a trickle system would be more suitable.
* By reducing excess evaporation. This can be achieved by covering bare soil. Mulches, as well as reducing weed growth will reduce evaporation. Compact groundcovers will slow evaporation from the soil but they will use a lot of water themselves. Larger plants will shade the soil and limit evaporation but they can make getting water to the soil in the first place rather tricky.
* Rainwater tanks are useful methods of gaining extra water.
The use of tanks in the city may require permission from your local government authority. Unfortunately some councils will not allow them at all, and some may require that they be of only a limited size and out of public sight. But if you can get one it can help save water rates as well as be a way of getting fresh rain water to drink. In some cities, however, it is not recommended to use rainwater for the household if there is any likelihood of pollutants being present in the rain water or collected off your roof as it passes across.
* By covering swimming pools and directing storm water into them (subject to the conditions set out in the point above). Have the pool surrounds sloping back a little towards the pool so that any splashed water will run back into it.
HINTS FOR DRY SANDY SOILS
A useful hint for planting in dry sandy areas is to dig the hole two or three times larger than the pot size that you have to plant. It is best to dig out half of the soil onto one side of the hole and one half onto the other. This gives you two piles of the sand from the hole, to one pile add well rotted compost, peat moss, well rotted animal manure or some loam. Mix all these together, pop some down the hole to bring it to the correct level then place your plant into the hole and backfill with the remaining soil. Tamp down the area around the plant and water in. Any left over soil can be used to form a lip around the plant to create a small basin to retain water. The idea with this system is to give the plants a good growing environment but at the same time allow them to become accustomed to the soil in which they are expected to grow in.
Many gardeners now incorporate moisture holding additives into the garden to give their plants a fighting start. Some of these products hold water in crystal form so that it is still available to the plants, or increase the water holding ability of the soil by altering the surface tension of the soil particles. Most of these products only last from a few months to about one year. They are short term remedies only but do help to get the plants established.
HUMID TROPICS
When planning for the humid tropical gardens, issues such as water availability, while still important, are not as crucial as they might be for drier areas. Humid tropic species have similar water requirements to most other plant species. They, as do most species, require the most attention and watering when they are young and more susceptible to drying out due to their size. Once established however, they will survive quite happily on the natural rainfall that they receive. In fact rainforest plants are no more difficult to grow as a group than any other group of plants. While there are individual species that ARE difficult to propagate or grow, the same is true of the entire plant kingdom and rainforest species should not be shied away from because of this.
Timing and quantity of rainfall needs to be noted or recorded. It is important to know when heavy rain periods are due and the quantity expected to fall. Adequate drainage should be considered in wet seasons to remove excess rainfall to prevent damage to the site and gardens.
The dry season may demand supplementary irrigations for young plants or new gardens.
Humidity, combined with the temperature, tends to encourage fast healthy growth on most species from warm climates. It also tends to encourage various diseases. Plants from tropical climates tend to have a natural resistance to most fungal diseases. Plants from cool climates planted in tropical gardens will usually succumb to most diseases due to its unsuitability.
One of the biggest causes for plant death in the tropics is the result of gardeners attempting to grow unsuitable plants in the garden. Plants that have silvery, hairy foliage are usually poor plant selections for this climate zone. Plants with glossy waxy leaves are good selections. Just like all things in nature there are exceptions to the rules so it is wise to refer to books like this or seek advice from local professionals.
The location of the site on a hill can dramatically influence rainfall and temperature even if the hill is in the middle of a tropical district. Rain may tend to come from only one direction, consequently, the property may be on the "dry" side or "wet" side. Whether facing north or south will influence temperature on the site.
High altitude districts within tropical areas will have much cooler temperatures than those properties sited near the coastline.
Handy hints to assist tropical gardeners include:
keep fertiliser up to plants due to extended growing/flowering periods.
mulch the soil and encourage ground covers to prevent soil damage during the wet season and to conserve water in the dry season.
regular pruning/trimming may be required to keep plants under control and neat.
select plants that prefer the climate - disregard plants that do not cope well with humidity.
COASTAL AREAS
Coastal districts have their own share of gardening problems. The climate tends to be slightly warmer in winter and cooler in summer than areas a little inland due to shore breezes. Plants therefore placed in a protected site away from costal winds tend to grow fast and healthy.
Plants exposed to coastal winds may be subjected to salt spray. This is regarded as the biggest problem for coastal gardeners. The selection of plants must therefore suit the general climate, tolerate coastal winds, withstand salt deposits on leaves and the ground, plus survive on usually sand, low fertility soils that do not hold a lot of moisture.
The range of suitable plants are generally those which come from similar environmental districts or those which exhibit:
hairy foliage
silver or grey foliage
compact habit
fine foliage
The further you go away from the seashore, the less effect the salt-laden breezes have on plants. In one garden it is possible to have sensitive ferns on the protected side of the house, and have Sheoaks (Casuarina), Coastal rosemary (Westringia) and New Zealand Christmas Bush (Metrosideros) on the other side exposed to the sea.
WINDY AREAS
Wind can cause severe damage to trees and shrubs. In storms falling plants can result in damage to buildings and other structures.
In warm climates strong winds come from storms; tropical climates are prone to cyclones and hurricanes close to the sea. Plants have however adapted to these climatic forces. Palms native to most islands do not fall over or get seriously damaged by strong winds or storms. Likewise many other plants are adapted to the climatic disturbances that occur naturally.
Brittle stemmed plants are prone to damage easily in even gentle winds. It is best to select trees and shrubs that exhibit flexible branches and limbs, strong roots, open canopy and vigorous growth.
Stalking may be needed on severely strong wind prone areas but should be kept to a minimum.
Windbreaks such as shade cloth, wind barriers, or similar can be used to reduce damage caused by winds. Planting a line of wind tolerant trees is one popular method used to reduce wind damage and intensity.
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