Damping Off
Any of a number of fungal diseases which attack seedlings, causing the stem to wither at the soil line, collapsing the plant. There is no good cure for affected plants, but any remaining plants can be saved by removing all the diseased material and moving the seedlings to a warm, bright, airy location. Proper thinning and avoidance of over watering, especially during cloudy periods is the best preventive measure.
Daylily, Dormant
Dormant daylily varieties 'die back' each year and go dormant. The dried stems and leaves can be left on the plant for protection from cold, or gathered and composted. They will tend to grow new leaves whenever the temperatures warm through the winter or early spring. The roots of dormant daylilies are hardy
Daylily, Evergreen
Evergreen and Semi-evergreen daylily varieties keep their leaves throughout the winter in warmer areas. These daylilies retain thier attractive leaves down to -8C. At -20C, top growth may die back, but roots are hardy.
Daylily, Extended Bloom
Flowers stay open after dusk, great for the evening stroll on the patio. Often termed 'night blooming' daylilies.
Daylily, Reblooms
One or more flushes of flowers follow later in the same summer, especially in warmer climates.
Deadheading
The removal of individual, spent flowers from a plant for the purpose of preventing senescence and thus prolonging bloom. For effective results, the ovary behind the flower must be removed as well.
Deciduous
A plant that drops its leaves in autumn. e,g, not evergreen. Though many deciduous plants can become partially evergreen in warmer climates e.g. shed and grow leaves regularly throughout the year.
Decussata
A latin word used in plant naming meaning - leaves arranged in an 'X' pattern e.g. opposite pairs at right angles to the pair beneath/above.
Dendron
A Greek word used in plant naming meaning - tree
Densiflora
A latin word used in plant naming meaning - dense or close flowers.
Denudata
A latin word used in plant naming meaning - bare or naked.
Determinate
Plant growth habit in which stems stop growing at a certain height and produce a flower cluster at the tip. Determinate tomatoes are short, early, have a concentrated fruit set and do not require staking.
Dicot
Any plant that has two cotyledons, or seed leaves.
Dieback
The death of new tips or shoots due to root damage, pests or disease. The plant will still be alive but just the new, softer growth can die back as the plant reserves its energies to mend that sick or damaged parts.
Dioecious
Having male and female sex organs on separate plants.
Distichum
A latin word used in plant naming meaning - leaf arrangements in twos
Division
The breaking or cutting apart of the crown of a plant for the purpose of producing additional plants, all genetically identical to the parent plant.
Dolobrata
A latin word used in plant naming meaning - shaped like a pick-axe
Dormant
The period of rest for a plant during which it shows no sign of life but is still alive e.g. hibernating. It also refers to seeds before they sprout e.g. they contain life potential but are temporarily completely inactive.
Double, Semi-Double
A flower with more than the normal number of petals, sepals or florets; in some cases petals or staminodes may replace stamens. A double form may be designated botanically by flore pleno, plena or pleniflora.
Drill
A shallow furrow or trough in the soil into which seeds are sown. Often made with a broad single tined hoe with the aid of a planting line for straightness.
Dripline
The circular area under a tree from the trunk to the outside tips of the branches e.g. where the bulk of the rain run-off will fall to the ground. This generally co-incides with the greatest density of fine roots which are most efficient at taking up moisture.