Bird Food

Will Nyjer Seed Sprout Under My Feeder?

Rarely, if you live in the United States. Imported nyjer must be heated to 248°F (120°C) for 15 minutes before it is sold. In Britain it is not heated at all, and it comes up under bird tables every autumn. The rule country by country, what the heat is really aimed at, and what is more likely growing under your feeder.

Nyjer seed bought in the United States should not sprout under your feeder, because federal law lets it into the country only after heat treatment. That is the answer most bags and most guides give, and for a US buyer it is the right one. Where it goes wrong is the reason. The heat is there to kill the weed seed mixed into the crop, not the nyjer, and outside the US many buyers get no heat treatment at all.

So two answers circulate. American sources say nyjer is "heat-treated prior to importation to prevent sprouting", as Project FeederWatch puts it. In Britain, nyjer plants with dodder climbing them are a regular autumn sight under bird tables, which is hard to square with seed that cannot grow. Both are describing their own country correctly. The difference is a rule that exists on one side of the Atlantic and not the other.

The US rule, and where 248°F comes from#

The rule is 7 CFR 360.400. It says niger seed is "commonly contaminated with noxious weed seeds", including dodder (Cuscuta), and that it may be imported only if it is treated on arrival at the first US port, or before shipment at a facility abroad that APHIS, the USDA's plant health agency, has approved.

The requirement is older than that section. Audubon dates the first heat sterilization mandate to the 1980s, after dodder contamination, with stricter rules in the 1990s when infestations briefly stopped imports. The temperature arrived with a December 2001 APHIS proposal: imported niger seed "must be heat treated at 248 deg.F (120 deg.C) for 15 minutes". The final rule in August 2003, effective September 19, 2003, added the option of treating abroad. In 2010 APHIS copied the requirement into the noxious weed regulations, noting that "most niger seed is not imported for use as nursery stock but as birdseed".

The Wild Bird Feeding Institute, the industry body, gives the current schedule as T412-a, heat treatment at 248°F (120°C) for fifteen minutes, and says four facilities in the United States and India are licensed to run it. The scale is large: a 2002 North Dakota State University report put US demand at 70 million pounds a year, all of it imported.

What the heat is for#

The 2001 proposal is plain about the target. The treatment then in use was aimed at dodder, but niger can also carry seed of onion weed, African couchgrass, red rice, kodo millet, mesquites, tropical soda apple, witchweed and liver-seed grass, all federal noxious weeds. The old treatment "is not effective against those additional noxious weed seeds", so APHIS set the hotter one. Nothing in the rule asks for the nyjer to be dead. British botanist Gordon Hanson says the same from the other side: US nyjer is heat treated "not to kill the Guizotia seeds" but to destroy the viability of the dodder.

Killing dodder does not take much. In a 2016 Korean quarantine study, Kyoung, Moon and Oh found dodder seed devitalized at 120°C after 5 minutes, at 100°C after 15 minutes, and at 85°C after 2 hours. The US schedule holds 120°C for three times as long as the study needed. The same study found that seed of two garden daisies, cosmos and China aster, kept the same vigor as untreated seed after 85°C for 2 hours or 90°C for 30 minutes, both schedules that killed dodder. Nyjer is a daisy too. The study did not test the daisies at 120°C, and we found no published germination test of US nyjer after treatment.

That leaves the institute's own word as the best statement on nyjer itself: sprouting is "unlikely after treatment at such a high temperature". Unlikely is the honest answer. "Cannot sprout" is a claim nobody has published a test for.

The rule by country#

We read the rule text for each place below. Only one names nyjer and a temperature.

The European limit is there because of birdseed. In 2010 the European Food Safety Authority found that livestock feed is processed in ways that destroy ragweed seed, while bird feed "often contains significant quantities of Ambrosia seeds and remains unprocessed". So Europe chose to limit the weed seed in the bag instead of heating it, in the same annex that sets its feed limits for aflatoxin. For readers in Canada, the directive alone does not promise that a bag of nyjer was heated. If it matters to you, ask the retailer whether the seed was treated.

What grows from untreated nyjer#

The best record of what untreated nyjer carries is Hanson's, published in British & Irish Botany in December 2019. For ten years he sorted 1 kg retail packets with a hand lens and tweezers and grew out what he found. Ethiopian exporters quote 98.5% purity; he found the bagged product "nearer to 99.8%". Britain buys around 10,000 tons a year, against over 40,000 in the US.

What came up, with the years he recorded it:

• Nyjer itself. Wild nyjer plants have been recorded in Britain since 1861 and in about 140 hectads (10 km grid squares). In cool summers it may not flower in the south until October.
• Yellow dodder (Cuscuta campestris), every year from 2009 to 2018, often seen "scrambling up the two-metre tall stems" of nyjer under bird tables.
• Johnson-grass. Most packets held about half a dozen seeds, but they germinated only in 2010 and 2011.
• Common ragweed, in 2009 and 2011, and thorn-apple (Datura), which local papers have called "the plant from Mars".
• Apple-of-Peru, a frequent contaminant, virtually every year.

Two things follow for a reader anywhere. Nyjer is clean seed, at well over 99% pure, so the weed load per feeder is small. And when it is not heated, the impurity that turns up most reliably is the very one the US rule was written for.

What is sprouting under yours#

If you are in the US and something is growing under a nyjer feeder, work through these in order.

1. Seed from another feeder. Most yards with a nyjer feeder also have a mix or sunflower nearby, and cheap mixes carry live grain and weed seed. Millet is the usual grass; our page on weeds under a bird feeder matches each ingredient to the weed it brings, including pigweed and Palmer amaranth, and white millet is a common mix filler.
2. A blend, not straight nyjer. If the bag is a finch blend, read the ingredient list. The import rule covers only the nyjer in it.
3. US-grown nyjer. The rule covers seed "imported into the United States". A short season variety, EarlyBird, let growers in Minnesota and North Dakota raise the crop in trials from 2002, with a growers' cooperative behind it. Seed grown here is never imported, so the heat rule does not reach it. If a bag says grown in the USA, assume it can sprout.
4. A treated seed that survived. Possible, since no test proves otherwise, but it is the least likely of the four.

A nyjer plant that does come up is a yellow-flowered daisy, and Hanson describes stems two meters (over 6 feet) tall. Dodder is a parasite: Canada files it with its parasitic plants, and Hanson describes it "scrambling up" the nyjer stems.

What to do about it#

• Pull seedlings before they flower, roots and all, and bag them rather than composting. If you find dodder, pull the plant it is climbing as well.
• Keep seed off the ground. FeederWatch notes that the small ports on a nyjer feeder stop seed falling. A catch tray under the feeder, emptied weekly, catches what still drops; see seed mess under feeders.
• Buy straight nyjer from a store that sells a lot of it. Fresh seed matters more for whether goldfinches, pine siskins and redpolls eat it than for sprouting; the nyjer seed guide covers how to tell fresh from stale, and storing bird seed covers keeping it that way.
• Weighing nyjer against other finch food? Nyjer and sunflower hearts are compared on cost, waste and the birds they bring in nyjer vs sunflower hearts.

What this page cannot tell you#

We could not open the APHIS treatment manual itself; the 248°F, 15 minute figure comes from the 2001 APHIS proposal and the Wild Bird Feeding Institute's statement of the current schedule. We found no published germination test of treated US nyjer. For Canada we read the CFIA directive, not individual import permits, so we cannot say how nyjer sold there is treated in practice. We do not know how much US-grown nyjer is on sale today. And the British record is one botanist's ten years of sowing packets in Hertfordshire: careful work, but one person's.