Harvesting Draba Seeds

This could pass as a Martian landscape, but it is actually a portion of the seed I harvested today from my container grown Draba cuneifolia.

The container was so crowded with Drabas that the flower stalks had woven into one great mass.  Any attempt to harvest seed from one plant caused all of the neighboring plants to dump their seed load.  More than enough seeds had already fallen back into the container, so I had to find a harvest method that could effectively remove the remaining seeds from the plants without additional losses.

The Draba seed pod is divided into two halves with a thin, semi-transparent membrane running through the center.  Seeds are arranged in two rows on each side of the membrane.  When the seeds are ripe, the two outer coverings of the pod begin to peel back at the bottom, leaving the seeds exposed.  At this point, it doesn’t take much disturbance to cause the seeds to fall free.  In the past, I have harvested seed by simply bending the plant over a small cup and giving it a couple of taps.  The seed fell into the cup and that was all there was to it.  That method doesn’t work when the tangled plants all acted as one unit.

I decided to try using my shop vac as a harvester.  My shop vac is a bagless model, so I took a clean sweeper bag and modified it to fit the inlet pipe on the inside of the shop vac dirt chamber.  Then I directed the sweeper hose towards the plants and the seeds quickly disappeared.  The shop vac is not a high end model, so the air flow past the plants was really kind of gentle and did little more than pull away loose parts.  I just hoped everything was ending up in the bag. 

 

Fortunately, the sweeper bag stayed in place through the entire operation.  I sucked in a lot of seed pod covers, along with a little bit of dirt, but it looked like there was also some seed in the collection.

A closer examination revealed plenty of seed hidden beneath the seed pod parts.

I had to cut the sweeper bag in half to remove the seeds, but I was happy with the harvest.

Draba seeds are tiny things.  That’s a normal sized nickel beside the seed pile.

This is what I ended up with after sifting the mess through a screen to separate out the seed.  That’s five grams of fine Blue Jay Barrens Draba cuneifolia seed.  I couldn’t find any figures specifically for Draba cuneifolia, but similar Draba species average about 6,000 seeds per gram.  That means there are 30,000 seeds in this vial.  I’ll be scattering this seed back on the barrens in the same area from which I originally collected seeds for my container grown population.  I think I’ve repaid that loan of a few seeds with adequate interest.

Seed Harvest

This was a rough year for the small winter annuals that live in the barrens.  These plants begin their growth in the late fall and flower in early spring.  They grow as long as sunlight is available, but this year, frequent snowstorms kept the ground covered for most of the winter. When winter finally ended, the plants had developed to just a fraction of their normal size.  Small plant size corresponds into a reduced seed crop.  For a plant that dies following seed production, fewer seeds likely mean a reduced population size the following year.  Several bad years in a row could eliminate a population.

My container grown plants came through the year in excellent shape.  Unlike their wild counterparts, these plants displayed the best the species can produce.  They proved an excellent example of how slightly different growing conditions can make a big difference in results.  The Leavenworthia uniflora shown here are as robust as any I have ever seen.

I grow plants in containers so that I can observe the daily changes in plant development.  A secondary goal in raising the more rare species is to produce seed that can be used to augment what is being produced naturally.  The original seed for these plants came from the barrens of Blue Jay Barrens.  Extra seed produced in containers is returned to the site of the wild population. 

The fruits are stuffed full of seeds.  This is about an average yield for the container grown plants.  Those in the barrens only produce four seeds at best.

I’ve been collecting seeds from the container for a week now.  The photo above illustrates a typical day’s harvest, a total of about 40 fruits.  I harvest the fruits just as they begin to split and expose the seeds.  I miss plenty, so there are more than enough seeds left in the container for next season.

Harvested fruits are left to dry for a few days.

When the seeds have completely dried, they are stored in an envelope until planting time.

Once I harvest the last of the seeds, I’ll take them out and scatter them on the barrens.  Leavenworthia seeds need a period of hot weather to allow them to break dormancy and germinate in the fall, so it’s important to get them planted while there is still plenty of summer yet to come.  I’ve also found that it’s best to plant seeds at the same time they would naturally be dropping from the plant.  That way they are naturally going to get the treatment they need for germination.  Hopefully, the coming winter will be more conducive to Leavenworthia growth and the barrens will produce a record crop next year.