Broad-leaved weed testing
Order a standard herbicide resistance test for broad-leaved weeds
ADAS conducts standard herbicide resistance testing on the following broadleaved weeds: fat hen, mayweed, poppy, groundsel, sow thistle and chickweed. All species are tested with a sulfonylurea (metsulfuron-methyl) and a triazolopyrimidine (florasulam).
For fat hen samples, we also test for PS-II herbicides resistance (using metribuzin).
All our broadleaved weed test costs £200.
From 2026 as an alternative, we offer rapid leaf tissue testing for broad-leaved weeds, turning around results in 21 days.
Order your testPoppies
July and August are the best months to collect poppy seeds for testing.
The number of red flowers will start to decrease, and the green and brown seed heads will be visible. The seed pods can be harvested when they become a greyish-brown colour. You will notice that the brown seed heads will begin to open just under the lid and a row of holes will be visible. Small black seed should fall from the holes when tipped upside
- Cut the heads from the stem.
- Place the seed heads in the paper bag or envelope.
- Leave the seeds in a well-ventilated area, making sure the bag
- remains open to the air to allow drying of the seed heads.
- Before posting seal the bag/envelope with sticky tape to prevent
- seeds escaping.
A guide to collecting poppy seeds
Book a testMayweed
July and August are the best months to collect mayweed seeds for testing.
Heads should be collected when mature. The petals will have disappeared, and the central dome will be yellow/brown in colour. Mature seeds are black.
- Cut off mature seed heads when seeds are just beginning to shed.
- Place the seed heads in the paper bag or envelope.
- Leave the seeds in a well-ventilated area, making sure the bag remains open to the air to allow drying of the seed heads.
- Before posting seal the bag/envelope with sticky tape to prevent seeds escaping.
A guide to collecting mayweed seeds
Book a seed testChickweed
Collect ripe chickweed seeds at any point in June, July or August.
Instead of an envelope, you can collect using a large paper sack. Check chickweed plants for flowers and seed pods – the seed pods will always be green.
Mature plants have both flowers and seedpods present.
- Pull large quantities of chickweed and place in a paper sack. Do not pack it in too tightly but allow enough room for air to circulate.
- Place the open sack in a well-ventilated area where the plants can dry out. As they dry, seed will fall from the pods to the bottom of the sack.
- When dry remove the chickweed straw from the sack shaking any loose seeds into the sack.
- When the straw has been removed, tip the seeds into an envelope. Before posting seal the bag/envelope with sticky tape to prevent seeds escaping.
- Alternatively post a sack containing the chickweed plants.
A guide to collecting chickweed seeds
Book a seed testSow thistle
There are two species of annual sow thistle: smooth (Sonchus oleraceus) and prickly (Sonchus asper). It can germinate in either Autumn or Spring and flower in May or June.
Seeds are produced over a period of about 10 weeks. The time for collection is usually May until September. Check sow thistle plants for flowers and seed heads as flowering continues over an extended period.
- Pinch the white top of the seeds and pull them off the plant.
- Place the seeds and fluff in a paper bag or envelope.
A guide to collecting sow thistle seeds
Book a testGroundsel
Groundsel (Senecio vulgaris) has a short lifespan; seeds germinate throughout the calendar year. This enables it to produce several generations in one year.
Plants can shed seeds by early June so you can collect ripe seeds between May to October.
Check groundsel plants for flowers and seed heads. Flowering begins when the plants are small and continues over an extended period. While collecting, it may be advisable to wear a mask because fluff can get into your mouth or nose.
- Pinch the white top of the seeds and pull them off the plant.
- Collect 20–40 heads from different plants.
- Place the seeds and fluff in a paper bag or envelope.
A guide to collecting groundsel seeds
Book a testReady to send your sample?
When you have collected your sample, post your sample along with the order form to:
Herbicide Resistance Tests, ADAS Boxworth, Cambridge, CB23 4NN
If you would like a more bespoke test, or would like to test a weed that is not listed, please contact us at weeds@adas.co.uk.
What happens after you send your seed sample to us
Once we receive your sample, ADAS will acknowledge with a receipt.
Tests then take 8–10 weeks to complete with tests being sown every 2–3 weeks.
Please note: samples with poor germination may result in delayed or failed tests.
Results will be sent as soon as they are available.
As a guide, if seeds are received by the end of summer, results will normally be available by the end of the year.
Order your broad-leaved weeds herbicide resistance test