Glossary T

Taproot

Some plants have one main, thick root, which grows vertically down, to anchor them and act as a storage organ. There will often be smaller rootlets branching off this.

Taxonomy

The naming and classification system used to describe organisms and their evolutionary relationships with each other.

Tender

‘Tender’ corresponds to RHS Hardiness Rating: H2 with plants tolerating a Winter Minimum Temperature Range: 1 to 5

Plants described by us ‘tender’ are tolerant of low temperature but will not survive being frozen. Tender plants can be grown outside once the risk of frost is over.

Tepal

A term used to identify the outer part of a flower (perianth) when either it can’t be distinguished as either a petal or sepal. Or the sepals are coloured to act as petals in attracting pollinators.

In the case of Hellebores, the perianth is made up of coloured sepals, known as tepals, with the true petals occurring as very small structures around the stamen classed as nectaries.

Tetraploid

A plant with four sets of chromosomes, instead of a diploid plant which has the usual two.  This allows for more variation in hybridisation and breeding.

Thinning Out

To reduce the number of seedlings in a given area or row. If seed germination has been very good or seed sowing was overly generous you may need to thin the seedlings out to allow adequate space for plants to mature. This may be done successively as plants grow.

Tilth

Cultivated soil that has been prepared for crop growth.

Top Dressing

The process of mulching the tops of containers and pots with gravel or bark both for aesthetical reasons and to help retain moisture.

Transpiration

Process by which plants take water in through their roots and loose it by evaporation from the pores in their leaves

Triploid

A plant with three sets of chromosomes, instead of a diploid plant which has the usual two.  Triploid plants are usually sterile.

Tuber

A modified plant structure, stem or root, enlarged to store nutrients, for survival, re-growth and asexual reproduction.

Stem tubers include Begonias, Cyclamen and Potatoes.

Root tubers include Sweet Potatoes, Dahlias and Hemerocallis.

Tunic

The papery protective covering found on many bulbs. This is formed from the old leaf scales (dead petiole sheaths) from the previous year’s growth.