There are many threats to plants in cultivation leading to their presence in our gardens beoming precarious. As native plants depend on their habitat (meadow, marshland, downland) so cultivated plants depend on the continued presence of gardens, nurseries, parks and allotments.
- Climate change and severe weather
Recent examples of this are flooding, water use restrictions, wind damage, harsh winters.
- Hardiness/poor suitability for area
Gardeners relish growing plants at the edge of their natural tolerance, this can endanger them if they are rare throughout their cultivation range.
- Difficulty in propagation or cultivation
Some plants are intrinsically difficult to propagate or grow; some are difficult because they require skills that are now scarce in the UK.
- Loss of habitat due to development (e.g. parks, gardens, allotments)
Over many years large gardens, parks and allotments have been used to build housing and offices, or for roads or sporting facilities.
- Change of use of habitat (e.g. using a flower garden for growing veg)
Changing fashions in gardening mean that features that used to be common in large gardens are rarely seen. Currently fashionable uses (vegetable growing,bee-keeping, outdoor eating) tend to replace island beds and bedding displays.
- Destruction or rendering unsuitable of habitat by human activity (e.g.vandalism)
Vandalism is responsible for many plant losses in parks and allotments, and has in the past resulted in the withdrawal of whole National Collections. A reduction in staff or change of use of a public area can very quickly render it unsuitable for growing plants safely.
- Competition from invasive plant species (or being designated an invasive plant species)
Invasive plant species are vigorous competitors and acheive dominance at the cost of the plants around them. However many plants that are regularly grown in gardens and parks run the risk of being labelled invasive if the relevant legislation is inappropriate in terms of risk or species listed.
- Pests and pathogens
Due to the nature of trade and travel, once a new pest or pathogen has been introduced to the UK, it is likely to spread. Recent examples of plants endangered in this manner include Ulmus (elm), Fraxinus (ash), Impatiens (busy lizzie), Fuchsia.
- Loss of skills needed to propagate or cultivate
Horticultural education has long been underfunded, and as a result many of the specialist skills that would have been practised by gardeners are now quite rare. This means that plants that rely on use of these skills to be grown are likely to be avoided.
- Economic fluctuations (e.g. nurseries going out of business)
Rarer and more specialist plants tend to be grown by small, specialist nurseries. By their very nature these nurseries are not financially robust and are vulnerable in times of poor economic stability.
- Changing fashions in plants, lack of aesthetic appeal
Plants are very affected by fashion, at present it is unlikely that there are many gardeners craving island beds planted with dwarf conifers and heathers; or a window full of housplants in macramé pot-holders. Sadly this means that during the periods when they are out of fashion, there is no financial return in maintaining a large range of these plants and they die out. One day, Heuchera and Hosta will become unfashionable, and the huge number of cultivars now grown will shrink as plants become extinct.