GROWING UP TOUGH IN MIN-TILL.
Dandelion or Taraxacum officinale can quickly invade min-till fields, where this weed adapts well to the surface cover and good soil moisture conditions of a low disturbance system. Thousands of seeds with a parachute-like pappus spread on the wind, invading any part of a field.

The seeds from dandelion germinate on the soil surface at 10 to 20 degrees Celsius. Optimum germination occurs in full light on bare soil. Germination may be reduced by the shade of a crop canopy or heavy surface residue; buried seeds will not germinate at all. Seedlings quickly develop a taproot, and by fall or early spring they can have a well-developed crown.

As the seedlings mature, they become long-lived, taprooted perennials. The crown divides to form numerous branches. Dandelion can also reproduce from pieces of taproot, especially the upper sections of the root, which have greater viability. Taproots of mature plants that are injured by tillage will form callus tissue which can generate new plants.

Dandelion can present a very difficult control problem if they grow late into the fall and resume growth in the cool temperatures of early spring. The main flowering period is April to May with some flowering in late summer. Healthy plants remain dormant or form a rosette during mid-summer and resume growth and flowering from late-August to mid-October.

SEEDS: STRENGTH IN SIZE OR STRENGTH IN NUMBERS.
In the Compositae plant family, which includes dandelion, black-eyed susan, oxeye daisy and the thistles, what we call the flower is actually a head - i.e. a whole inflorescence of many small flowers (florets) clustered tightly together to resemble a single large flower. Dandelion have strap-shaped (ligulate) florets whose sepals have become soft hairs (the pappus, which enables the seed to float on the breeze). The ovary of each floret matures into a firm-shelled fruit (achene) containing a single seed. Each plant can produce up to 20,000 viable seeds that can remain viable even after digestion by ruminant livestock.

There are several different genotypes that make up dandelion populations. Those with high seed production tend to invade disturbed areas, while those that produce fewer seeds but are larger and more competitive tend to invade established pastures. While both can be found in min-till, the larger, more competitive types present the more difficult control problem.

AVOIDING INFESTATIONS AND TAKING CONTROL- IT'S ALL IN THE PLAN.
Sweep tillage, low glyphosate rates and many of the commonly used, in-crop herbicides will only suppress mature dandelion. Perennial or established winter annual dandelion cut off by tillage can re-grow later in the spring from deeper roots, emerging after the in-crop spray and reducing overall control.

Dandelion infestations often show up two to three years into a direct seeding system, depending on a local seed source. To avoid infestations, plan your dandelion control strategies to hit actively growing juvenile plants in the first fall or spring after germination.

• Products containing glyphosate, dicamba, 2,4-D or amitrol are effective on seedlings in the fall.
  
  
• By spring, glyphosate at rates above 0.5 to 0.75 L/acre or Amitrol_ 240 will control actively growing juvenile plants before planting.
  
  
• Curtail* M, Attain* and Prestige* are labeled in cereals for post-emergent control of juvenile dandelion up to 15 cm across.
  
  
• Dow AgroSciences products containing the new active ingredient florasulam are even more effective for post-emergent control of juvenile and more mature dandelion.
  
  
• Dow AgroSciences has also recently received registration for Eclipse, a product developed to broaden the weed control spectrum for glyphosate-tolerant canola. Eclipse controls dandelion (and wild buckwheat and thistles) better than a straight glyphosate application.

Glyphosate can be quite effective on actively growing dandelion in fall. The best timing over the past several years has been mid-September to mid-October. The critical factor for late fall is evidence of re-growth accompanied by good growing conditions for a few days before application.

For spring, glyphosate at higher rates or Amitrol 240 will suppress dandelion and reduce their impact on crop yield. However, they must be applied 7 to 14 days before seeding because of crop safety concerns.