Gardening Tips: Plastics in the garden
Plastics have a number of qualities that make them suitable for use in the garden; they are light, easily cleaned, tough, durable, not easily corroded and versatile. They are also very good insulators of heat and are generally cheaper than naturally occurring materials, because the raw materials from which they are made are mostly very inexpensive.
A major drawback, on the other hand, is that they may suffer adverse changes with a rise or fall in temperature; for example, a plastic wheelbarrow will melt if placed too near a bonfire, whereas a metal one will merely get hot. Some plastics become rigid and may crack when exposed to prolonged frost. The other major disadvantage is that clear plastics, such as the clear polythene sheeting which is often used for cloches and greenhouses, tend to deteriorate with exposure to sunlight and lose their transparency.
There are a number of different kinds of plastic from which gardening aids are made; a basic division is into rigid plastics and flexible plastics. Polystyrene is a rigid plastic that is made into pots and other plant containers, seed trays and propagators. PVC (polyvinyl chloride) is a rigid plastic used for cloches, frame lights, greenhouses, fences, trellises, planting stakes, gardening boots, gardenmakers and other items.
The most commonly used plastic is polythene, which is available as either a rigid or flexible material.
Polythene is unaffected by most chemicals, is rotproof, frostproof, light-weight, impermeable to water (though it allows air to pass through it) and has good heat and light transmission. Because it is impermeable, it retains moisture, which can present a problem; polythene-clad greenhouses are prone to build-ups of condensation. Here the remedy is to provide adequate ventilation. The moisture-retaining property of polythene can be a great advantage, however, as when black polythene sheeting is used as a mulch.
After two or three years’ exposure to the ultra-violet rays in sunlight, polythene sheeting becomes brittle. It also tends to become scratched by grit and other particles blown by the wind. However, it is easy and quite cheap to replace the worn-out sheeting with new material.
Plastics for tools and appliances
Plastics are being used increasingly in conjunction with wood and metal in the manufacture of tools and other garden equipment.
Many modern makes of spades, forks, hoes and other tools have shafts covered with a thin skin of plastic, which makes the tools more comfortable to handle and warmer to the touch in cold weather. The plastic coating also protects the wooden or metal shafts from rotting or becoming corroded.
The plastics in present-day use are not equal to the strains and stresses with which spade blades and fork tines have to contend, but they are successfully used for the bodywork of wheelbarrows, for the casings of chain saws and other power tools and for watering cans. In such cases, the toughened plastic is able to withstand considerable impact.
As plastics are resistant to corrosion by most chemicals in common garden use, they are widely used to make equipment used for applying weedkillers and pest- and disease-control sprays.
Protection of crops
Plastics find many uses in the protection of crops from birds, mammals and insects.
Rigid and flexible plastics are combined to produce bird-scarers of various types. The commonly used, ‘windmill’ type either scares the birds directly by means of coloured rotor blades, or drives some ingenious contrivance that makes a series of noises like football rattles.
Mouldings of imitation hawks are also available; these are suspended on a thread so that they move with the slightest breeze and frighten off the birds.
Plastic netting is extremely useful for protecting crops. Made of high density polythene, nylon or polypropylene, it is rot-proof and fungus proof. It is available in a wide range of different mesh sizes, and can be used either as a temporary structure or a permanent fruit cage.
Fine-mesh plastic netting is ideal for protecting crops against frost, or as a windbreak. Although more expensive than wire netting, it will last much longer and is available in a black colour which harmonizes much better with the surroundings than bare metal. Netting is also very useful for training crops such as runner beans, and for supporting the heavy fruit of melons.
Other useful items are plastic plant collars, which either physically prevent insects from reaching the plant, or are impregnated with some chemical to kill or deter harmful insects. These can be used to protect brassicas,and carrots from attack by root flies. Plastic drain pipes are very useful for blanching celery and ; because they weigh much less, they are much easier to handle than traditional clay ones.
Plastic tree bands covered with grease or some other sticky material are excellent for trapping pests such as winter moths as they ascend the trunks of fruit trees to lay their eggs among the branches.
Plastics for supports
For supporting crops, it is possible to buy lightweight steel tubes covered in green PVC. Although more expensive than bamboo or wooden stakes, they last far longer and are rustproof, rot-proof and disease-free: no treating with preservative is necessary as with wooden stakes.
The best method of securing a newly-planted fruit tree to its support is to use one of the modern plastic tree ties, which are provided with an adjustable buckle and a cushioning pad.