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Parthenocarpic fruits are fruits that develop from unfertilised female flowers – in other words, they are seedless by nature. Cucumbers, for example, are able to produce parthenocarpic fruits.

The location note “partially shaded” describes areas that receive around three to six hours of direct sunlight a day. Often this is morning or evening sun, while the position lies in shade for the rest of the day.

Perennial plants – which includes herbaceous perennials, shrubs and bushes – have a lifespan of more than two years. They last through winter, produce new shoots in spring, and delight us with their enduring presence. Sometimes the plant’s top growth dies back (as with herbaceous perennials) while the underground parts – the rootstock or rhizome – remain alive.

Phosphorus is an important plant nutrient, needed above all for the plant's energy supply. It plays a key role in root development as well as in flower and fruit formation.

Photoperiodism describes plants' ability to respond to the length of day and night. It governs key developmental processes such as flowering, bud formation, sprouting and dormancy.

Phytoncides are biological substances produced by plants and released into the soil, water or air. These compounds can either inhibit or promote the growth of neighbouring plants, as well as affect the life of insects, worms, bacteria and fungi.

Pinching out is a horticultural technique that involves removing the growing tip of a plant's shoot with your fingers or scissors. This simple step slows upward growth and encourages the plant to branch out more strongly. The result is a more compact, bushier plant that often flowers more freely.

Plant pests are animals, plants, bacteria and viruses that damage plants through their behaviour or characteristics. Even from this list alone, it's clear that plant pests form an unmanageably large and varied group.

Plant spacing refers to the distance that should be kept between individual plants when planting or sowing. It depends on the growth habit, the plant's final size and its nutrient requirements. The right plant spacing helps plants develop healthily, get enough light, and avoids mould or competition for nutrients.

A polytunnel greenhouse is a freestanding small greenhouse covered with polythene film rather than glass or rigid plastic. As with a tent, the film is stretched over curved steel tubes.

Potassium is a key plant nutrient that regulates water balance, cell stability and plant resilience. It plays a major role in stem strength and overall plant health.

Powdery mildew is a fungus that spreads as a mealy, white coating on leaves, stems, buds, flowers and fruit. Warm, humid weather favours its spread. In cases of heavy infestation, plant parts die off. Affected plant parts should be removed and destroyed immediately.

Pricking out is the process of separating out individual seedlings so that they have more room to grow.