This simply means a young tree, usually less than a year old.
These are crops that are harvested during the main growing season for that plant. For example maincrop potatoes are harvested in august and September, as opposed to early varieties that are harvested through June and July.
A marginal plant grows in the moist on the edge of a pond or stream, where the roots can easily access the shallow water. A good example of a marginal plant is flowering rush.
This is the climate or conditions of one specific and usually small area, which are different from the climate of the surrounding area. For example your garden might have its own microclimate if it is sheltered from prevailing weather, or has heavy clay soil that retains water.
This is a border that contains a variety of different plants, usually mixing both shrubs and herbaceous plants.
Modules are very small containers that are used to grow seedlings. A module tray is a tray with lots of little compartments for growing seedlings, not unlike and ice cube tray.
This is a plant that produces two flowers, one male and one female, rather than one flower that contains both male and female reproductive parts. The two flowers usually form on different parts of the plant.
Moss is a flowerless green plant that grows in damp conditions over ground as a carpeted effect. It can be a problem in lawns, when moss grows in the grass and can be difficult to remove.
Mulch is a substance used to cover exposed soil for several reasons; to protect the soil from erosion and weeds, to insulate the soil and plant roots over winter and to reduce erosion. Mulch can be biodegradable, for example organic compost, which breaks down over time and adds nutrients to the soil. It can also be non-biodegradable, for example slate chippings, which add a decorative element to your beds and borders.
This is a type of lawn mower that cuts grass into very fine particles which can then be left on the lawn to break down and become part of the soil underneath.