2103 - Weeds Flashcards
What is a weed?
A plant in the wrong place.
Can refer to any plant that has found its way into a garden and is unwanted.
Many weeds are very successful wild plants which can colonise areas of bare soil quickly.
Many can regenerate from tiny pieces of root or stem, so can be difficult to fully remove.
Why eliminate weeds
- compete for nutrients, water and light
- can act as host for Pests and Disease
- aesthetic reasons
- Can smoother cultivated plants (Hedge Bindweed)
- Generally destructive Fallopia japonica (Japanese knotweed)
- reduce quality of turfed surface, Poa annua, Veronica persica
- contaminate harvested seed stock
Annual Weeds (and ephemeral)
Germinate from seed, grow and set seed, die within one year. (numerous times if Ephemeral)
Main problem in regularly cultivated ground.
Annual:
Veronica persica (speedwell)
Poa annua
Galium aparine (cleavers)
Ephemeral:
Stellaria media (chickweed)
Capsella bursa-pastoris (shepards purse)
Senecio vulgaris (groundsel)
Can be prolific seed setters, thousands per year, which can remain dormant in the soil for many years.
Perenial Weeds
Reproduce by seed and vegetative growth. Can live for many years and regrow each new growing season.
Can often regrow from small pieces of root, which can b difficult to completely eradicate.
Taraxacum official (dandelion) Ranunculus repans (creeping buttercup) Bellis perennis (Daisy) Pentaglottis sempervirens (alkanet)
Perenial vegetative reproduction - Tap Roots
Act as storage unit that grow deep into the soil.
Taraxacum officinale
Rumex obtusifolia
Perenial vegetative reproduction - Rhizomes
underground or ground level stems Elymus repans (couch grass)
Perenial vegetative reproduction - stolons/runners
modified stem that creeps along the surface producing new plants and adventitious roots.
Ranunculus repans
Fallopia japonica
Perenial vegetative reproduction - Tubers/bulbs
Swollen tubers acting as storage organs
Ranunculus bulbosus
Recently Cultivated soils
Mostly Annual & Ephemeral weeds
Poa annua, Veronica persica
Remedied by repeated hoeing, (Dutch hoe) or contact herbicide such as Fatty Acids
Herbaceous Perennial Border
Mix of annual and perennial weeds
Senecio vulgaris, Poa annua, Pentaglottis sempervirens
Remidied by hoeing or hand removing, Perennials may be removed with Translocated Herbicide (Glyphosate) but not advisable, normally this would be tackled prior to planting, as to not affect cultivated plants.
Annuals can be removed with Contact (Fatty Acids) but again care must be made to not make contact with cultivated plants.
Woody Perennial Border
Mixture of weed types
Galium aparine, Pentaglottis sempervirens, Rumex obtusifolia
Hoeing not advisable due to shallow roots of shrubs. Possible to hand-weed but with minimal disturbance to the root-zone.
Apply Translocated Herbicide, Glyphosate.
Lawns
Particular weeds on a lawn include
Bellis perennis, Ranunculus repans, Poa annua
Feeding lawn to boost grass growth, Repeated cuttings. Also selective herbicides, 2,4-D which will kill broadleaved (dicot) plant but narrow leave Monocots are unaffected.
Cultural and Physical controls
- Mulching 5 - 7cm
- Weed suppressing matting
- Hand weeding and hoeing
Care must be made to remove all root system or more can grow rapidly eg. Elymuss repans (couch grass). - Rotary cultivators
- Flame/Heat treatment
Herbicides cont… Contact
Will kill any plant they come in contact with.
Effective against annuals and perennial seedlings.
Ineffective against mature perennials with deep root systems.
Fatty Acids
Herbicides cont… Translocated
Non selective, moves through a plant and kills the roots.
Effective against Deep Rooted Perennials.
Glyphosate
