• #19 - Sep 2018 - Garden Stuff - © Sandy Lang - slang@xtra.co.nz
• 
  
• WEEDS
• September: Spring at last…! Pruning done…?
• 
  
• Weeds: Weeds are plants you don’t want. Most weeds grow from seeds. Aboveground, weeds compete with your plants for light and, belowground, for water and minerals. Some weeds produce ‘allelopathic’ (Google allelopathic) chemicals that poison other plants. Weeds are bad…
• 
  
• Weed seeds: When you buy seeds you expect 95+% germination. But weed seeds are not like that. If all germinated, the lot could be wiped out by e.g., a bad frost. Nature is cunning. Maybe 95% of weed seeds don’t germinate but lie dormant in the soil for a year or two or more (gorse 30 yr). Hence, the soil contains a vast ‘bank’ of dormant weed seeds. So while a frost might kill all those germinating this year, next year there will be another healthy flush of new weed seedlings from the seedbank. Weeds are survivors…
• 
  
• Weed seeds are programmed to germinate when conditions are right – light level, daylength (time of year), moisture, temperature. Because germination is mostly triggered by light, when soil is disturbed by pulling weeds out the seedbank is redistributed, many buried, dormant weed seeds now find themselves near the surface, and so germinate. Two weeks later you have a fresh crop of weeds...
• 
  
• Weed control methods…
• 
  
• Mechanical (beds): •Pull them out (damp weather, so roots come out too). •Hoe them (dry weather, so they dry and die). But pulling and hoeing disturb the soil, so both encourage germination of buried, dormant weed-seeds.
• 
  
• Smother (beds): •Cover with mulch. Many weeds die, a few break through, pull them out. The disturbed soil stays dark, so more weed seeds don’t germinate.
• 
  
• Cook (paths, edges): •Gas flame (handheld blow torch - dry, still weather). •Steam (handheld steam cleaner – dry, still weather, extend nozzle with 6” of garden hose to slow jet - e.g., Karcher $188) •Boiling water (boil the jug, pour on).
• 
  
• These methods kill only the tops of the weed plants. Some weeds regrow weakly from tap roots. Cook them again before they get big. More will die. Councils use flame and steam. Especially around schools where chemical weeding is unwelcome...
• Chemical (beds, paths): •Use an ‘organic’ weed killer or •use Roundup (glyphosate). Many chemicals are dangerous - even many ‘organic’ chemicals. There’re many familiar, dangerous chemicals in your home (glues, paints, petrol, bleach, toilet cleaner), glyphosate is just one of them…
• 
  
• Most NZ horticulture uses glyphosate. Councils use glyphosate. So, use chemicals but always use chemicals with care and DON'T spray a fine mist in windy weather - wait for a calm day and set the nozzle to 'droplets' not 'mist'…
• ___________________________________

•