Nothing sweet about this honeysuckle

Tatarian honeysuckle (Lonicera tatarica) is the scourge of many grasslands in my area. An invader from Asia,  it is quick to invade grasslands where it forms dense thickets where little can grow underneath their canopy. But how can they invade these fields so quickly and successfully?

Tatarian honeysuckle invading a field at University of Toronto Mississuaga (left). Little vegetation can grow underneath the canopy of tatarian honeysuckle (right). The dead stocks in the foreground is crown vetch, which grows just outside of the honeysuckle's crown.

One solution to this conundrum is playing out right now in the very early spring. I was surprised to see on my walk this week that honeysuckles have wasted no time in producing their leaves, which is weeks ahead of other plants. By producing leaves so early they are getting a head-start on the growing season, and shading out any late comers to the light capture game. 

Tatarian honeysuckle with a fresh flush of leaves on March 15, 2016 in Mississauga ON

However, this early leafing strategy is just one of a trifecta of traits that make for a super weed strategy. These plants also hold their leaves long into the fall, typically weeks longer than native species, which allows them to capture more carbon than their native competitors. This strategy of holding leaves late into the fall is a common feature shared by many invasive shrubs successfully invading eastern North American forests and fields, as shown by Dr. Jason Fridley's research at the University of Syracuse. The final strategy these plants employ is perhaps the most exciting and cunning - they poison their competitors. Invasive honeysuckles secrete toxic phenolic compounds into the soil which inhibits the germination and growth of native competitors (see work by Dr. Don Cipollini here and also here). 

Why should we care about this invader from the far east? The spread of this invader in my local field (and in many fields throughout North America) is pushing out populations of native plant species like hairy beard's tongue (Penstemon hirsutus), Canada tick-trefoi (Desmodium canadense), early goldendrod (Solidago juncea), heart-leaved aster (Aster cordifolius), prairie anemone (Anemone cyldindrica), common milkweed (Asclepias syriaca), and common evening primrose (Oenothera biennis), to name just a few that are on their way out in the same field as this honeysuckle. These plants in turn support a wide diversity of pollinating bees, butterflies, beetles, flies and moths, plus a wide diversity of insects that only feed on these specific plant species. If honeysuckle prevails than this native biodiversity will blink out and the ecosystem will be fundamentally altered.

In other words, this honeysuckle isn't as sweet as its name suggests.