How to weed a bonsai

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File:Oxalis 01.jpg
Oxalis, a common bonsai weed, can spread by underground runners

Weeding Tips

Weeds compete with your bonsai for moisture, oxygen in the soil and nutrients. Many weeds have root systems that are well adapted to growth in containers, so your trees will need your help. Follow these tips to help keep ahead of the game!

How to Weed

  • Weeds may be shallow rooted, or deep rooted. Some weeds have bulbous roots and others are fibrous and very fine. You need to develop a strategy that works with each type.
  • Weeds spread by runners, seeds and stolons. If you find that the weeds are interconnected, you might need to poke around with a chopstick and pry them out, getting as much of the root as possible. Weeds can often regenerate if you leave any significant part of the root system behind!
  • Some weeds are brittle and others get such a good grip on the soil, they're hard to remove. Using two fingers to hold the soil around the weed down, grip the weed at its crown with a pair of tweezers and pull straight up.
  • If the weed breaks off at the rootcrown, you can use the point of a chopstick to dig up around it and pry it out; use the pad of your thumb against the stick to pluck it out.

When to Weed

  • Regular attention to maintenance weeding will help prevent a big problem later on. However, weed germination increases after rainfall, during the spring and late summer, and whenever you fertilize
  • Pay particular attention when you repot to remove any weed roots. These are usually the most fibrous, white roots in your bonsai pot. It's a great time to get tenacious weeds like dandelions, or invasive weeds like Baby's Tears
  • Deciduous trees can often be completely bare rooted during repotting. This is a great time to ensure that all the weeds and field soil have been removed.
  • Always weed carefully before fertilizing. You want to grow bonsai, not weeds!
  • It's especially important to get weeds like Dandelion before they bloom and spread to other plants!
  • Remember - weeding is a regular chore. Try to spend an hour or two every week doing weeding. It's an excellent opportunity to look over your trees more carefully. I like doing this in the early morning, when it's also possible to find pests like slugs and snails and remove them.

Some Guidelines

  • Avoid keeping groundcover (Irish Moss or Scotch Moss) in your bonsai pots.
  • Weed seeds remain viable for decades. You can remove the upper inch or so of soil from your bonsai pot and replace it in Fall. This will help rejuvenate the plant, keep a crust of spent fertilizer from developing and remove wind-scattered weed seeds that might fall into your pots.

A Few Common Bonsai Weeds

  1. Dandelion
  2. Oxalis
  3. Scotch Moss
  4. Irish Moss
  5. Baby's Tears
  6. Violet
  7. Common lawn grasses
  8. Hornwort
  9. True Mosses