Chickweed has continued to develop over the last month, with little opportunity to spray, so you could be dealing with some large plants. If the ley is established you can treat with Leystar or Envy @ 2LTS/Ha or 1 LT & 1.5LTS respectively for new sown leys and grass for seed with the benefit of clearing up some thistles docks and other common broad-leafed weeds and only 7 days stock exclusion. They contain Florasulam as well as Fluroxypyr which allows them to work well at lower temperatures, especially useful when there is large fluctuations in temperatures between night and day at the early part of the year. Alternatively Gal-Gone a straight fluroxypyr product offers a great solution if chickweed is your main problem @ 1LT/Ha and there is only 3 days stock exclusion for grazing. Remember that all these sprays will kill clover, so clover would need to be reintroduced 3 months later.
Clover safe options are available – please ring Sally Cornforth on 07590 767655 for more advice.