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    Thread: Stratifying seeds

    1. #1
      seanmckinney's Avatar
      seanmckinney is offline Senior Member
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      Jun 2004
      N. Ireland

      Stratifying seeds

      Last autumn I collected and brought in many iris seeds, before winter got cold I took them out and scattered them on the surface of soil in seedling trays sat in the pond. It was a mild winter here and there have been only a couple of night time frosts, 1/4 of ice would be the deepest ice seem this winter.
      The seeds have yet to germinate, they are wet as the soil is soaked.
      Should I lift the seeds and bung them in the fridge or freezer for a few days? I had hoped nature would do the trick but seamingly not, or is it still too early?
      The fridge will probably be 4C 40F, the freezer ... below 0C 32F. I could turn the fridge down a bit more or put the seeds in the cold compartment which will be only slightly below 0C 32F.

    2. #2
      CarolinaGirl is offline Inactivated
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      Apr 2004
      Lugoff, SC
      Here's a good article on growing iris from seeds:

      One Way to Plant Bearded Iris Seeds

      Paul Black

      (reprinted from AIS Bulletin, October 1994)

      There are probably as many ways to germinate bearded iris seeds as there are hybridizers planting them. Each of us has worked out some effective method to do this, based on our area's climatic conditions. One must also take into account other factors such as space limitations and whether areas where seed is germinated are to be used at a later time to grow named varieties. The following is what I have found to be effective for this region and my particular situation. What works here may or may not work in other areas without some adaptations. After having worked out all the kinks, I can now count on 70% to 80% germination each year.

      The seeds have been gathered, and this is where I already make a bit of a departure from some others. I rarely let the pod ripen to the point that it splits open. I harvest pods when they are beginning to shrivel and turn tan in color. After a couple of weeks of harvesting, I feel that what is remaining has reached enough maturity to be harvested, and I cut all remaining pods. I cut the ends of the pods with a knife and make a slit along the length of them. This allows me to pull the pod open and release the seeds into a cup to dry. If there are too many seeds to dry easily in the confines of a cup, I place them on a small paper plate to dry, then dump them, along with the tag, into cups which can then be stacked until it is time to plant. I have never seen any lack of germination from this slightly early harvesting method. It also saves having to pick up shattered seed off the ground and probably missing some that later sprout and become a rogue in the named plantings. Neither does it seem to diminish the supply of food available to keep the seedlings growing once they have germinated.

      After recording all the parentages, I am ready to plant the seed. Anytime from Halloween to Christmas seems to work quite well here. Normally, I try to plant around the third week in November, close to Thanksgiving. It seems a fitting way to celebrate Thanksgiving. I am thankful there are seeds and even more thankful when they germinate and are planted in the spring.

      There are several requirements that must be met in one way or another for bearded iris seeds to germinate. The first is that there needs to be a period of chilling lasting at least six weeks with temperatures being below 40 degrees F. The other is that the dormancy factor in the seeds needs to be leached away with a quantity of water after they are planted. The endosperm must be hydrated to be able to germinate. The seed must have oxygen in order to germinate. The chilling requirement is easily met here since we certainly have at least six weeks when it goes below 40 degrees. The other requirements are explained in the following text.

      I choose to plant the seeds in one gallon plastic pots so that I don't have to worry about dormant seeds lying around here and there in the garden if they had been planted into the ground. I shuffle plants around too much to have to worry about this. I use a commercial potting mix that is about equal parts of peat moss, ground bark, vermiculite and sand. This makes for a rather light planting mixture and some of my planting techniques compensate for that.

      The pots that I use have four to six wide drainage holes in the bottom, and to keep the potting mix from running out with the water, I use coffee filters and place them in the bottom of the pots. This works well for potting house plants too. With the filters in place, I add the potting mix and tamp it down with the bottom of another pot until it is about 2-1/2 inches from the top. I then sprinkle the seed over the mix with sometimes as may as 60 to 80 seeds in the pot. Because the potting mix is light, I cover the seeds with about one inch of mix and again tamp it down with the bottom of another pot. This is all done assembly line fashion.

      To help moderate the temperature of the pots and also help keep moisture levels constant, I sink the pots in the ground. I dig a trench not quite as deep as the pots and make sure the lower part of the trench is V shaped. This is so the soil doesn't pack around the drain holes and create a swamp in which the seeds have to reside. With an open space below the pots, the water is free to flow easily out of the pots. This helps achieve two of the requirements. First, it lets me run plenty of water over the seeds to leach out the dormancy factor, and secondly, it keeps the potting mix from becoming soggy and thus depriving the seeds of oxygen needed to germinate.

      The next step is to put on a mulch of ground leaves, straw, pine needles or whatever is available. I do this for two reasons. The potting mix is quite light, and if there is nothing to break the falling water, the seeds will float to the top and never germinate. It also provides all the other benefits of a mulch by keeping the moisture and temperatures constant.

      Pots should be watered weekly except when they are frozen. Fortunately, the latter is often the case here. The easiest way to water, although not the most consistent, is to lay a rubber soaker hose over the tops of the pots and let it run until the water flows through the mix. The other way is to use a breakwater on the end of the hose to provide a fine spray of water that doesn't disturb the mix too much. Of course, there is always the hope that Mother Nature will take care of the watering. As the weather begins to warm and the potting mix begins to dry more quickly, it is imperative that the mix never dry out or the seeds will not germinate. Do not equate this with keeping the mix soggy or, again, the seeds will not germinate from lack of oxygen.

      The most exciting time is early March when the potting mix begins to have a humped up appearance. This soil is being pushed up by the seeds germinating beneath it. You have now achieved success.

      Here in Oklahoma, it is common to get two or three weeks of very warm weather in mid February and this will often start the seeds germinating. For this reason, I keep a plastic tarp and mulch around to protect the seedlings in the event that temperatures are going to be in the low 20's. Unprotected, these newly sprouted seedlings will freeze and die.

      As the new sprouts begin to grow, I fertilize them with a 1/4 strength fertilizer solution with each watering. About six weeks after they have germinated and are about two inches high, I knock them out of the pots and plant them in the garden and hope for that next Award of Merit winner or better yet -- dream big, a Dykes Medal winner.

      Many of these techniques, I have learned the hard way. One year I used garden soil instead of potting mix, and the water didn't drain well. There was very little germination that year. Another year, we had a very warm February, and I wasn't aware that the seeds were germinating. Then, it dropped to 10 degrees. There was less than 1/2 percent germination that year. As with growing anything, Mother Nature always has something new to throw at us, and even the best of plans will still meet with disaster at some time. When it happens again, I'll let you know what adjustment I have made to counter it.

    3. #3
      seanmckinney's Avatar
      seanmckinney is offline Senior Member
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      Jun 2004
      N. Ireland

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