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Chickweed, Stellaria media, is best thought of as a delicious rather than a pernicious weed. Its young leaves are packed with vitamins, so it makes a healthy addition to salads. However, it can also harbour greenfly and spider mite, so remove it immediately if it appears in your greenhouse.
Solution
Organic
Hand weed or hoe out seedlings as they appear, or smother them with a good layer of compost or mulch. The most effective control is to remove the plants while they're seedlings.
Chemical
Use a total weedkiller, such as glyphosate. Avoid spraying on a windy day, or when the weed's near other desirable plants.
