Cultivating Questions: Purslane, Portahoopies and Plow Planted Peas
by Anne and Eric Nordell
In the Winter 2000 SFJ, we looked at a number of cover crop options for improving phosphorus availability. Option #419 was plow planted peas following double-cut rye. This cover crop sequence also turned out to be very effective at setting back purslane, a slippery weed which had so far eluded our cropping system in the house gardens. We would like to take the opportunity here to show how we used plow planted peas to reduce purslane pressure before planting the portahoopies.
For those not familiar with this tasty, nutritious weed, purslane can be a real challenge to manage in vegetable crops for a number of reasons. The seeds of this weed remain viable for many years in the garden, and generally do not germinate until hot weather — that is, after many of the market garden crops have already been planted. To make matters worse, this succulent plant often reroots after cultivation. Purslane also grows so close to the ground that it is impossible to control by mowing.
For all of these reasons, we have found that midsummer smother crops are more effective at controlling purslane than our usual cover crop/bare fallow sequence. These photos show just how we did it in the hot, dry summer of 1999. We repeated the same cover crop sequence in the cold, wet year of 2000 with equally good results, preparing a patch in the house garden for this year’s early hoophouse production.
#1: We clipped the cover crop of rye in this fallow area a couple of times during the spring of 1999. The resulting mulch of rye clippings shaded the soil sufficiently to prevent the purslane from germinating. Then, the end of July, we broadcast two types of pea seed on top of the rye clippings and plowed them in at the same time.
#2: We adjusted the old walking plow to cut a shallow furrow just 2-3″ deep. “Skim plowing” the rye residues placed the pea seed at the perfect depth for quick germination in hot, dry conditions. In fact, the heat loving cow peas popped out of the ground in just four days. On the other hand, it took almost twice as long for the cool season Canadian field peas to emerge, about the same time as the first of the purslane began to appear.
#3: As the weather cooled off toward the end of August, the field peas really took off, outgrowing their cousins from the South with vines four feet long. By using the two types of pea seed we effectively shaded out the purslane despite changes in the weather.
Yes, the purslane germinated and grew in the understory of the peas, but it did not receive enough sunlight to make seed. So you see, the key to our weed control strategy is the use of a well timed smother crop to intentionally germinate a generation or two of the purslane but prevent this weed from setting more seed. In this way, we can reduce the weed seed bank of purslane in the soil surface.
#4: By December, the July planted peas had already died off, producing a significant, soil protective mulch. At this point, we were no longer concerned about the purslane in the understory as it had long since died off with the first hard frost.