Type of potting material for planting penstemon seed

I can't offer much advice on western species since I live in Minnesota.  I have started some seed of western species in regular seed starting mix and got them to germinate.  I then moved some of the seedlings into larger pots with a more suitable substrate.  The initial germination may not be too much of a problem but keeping them long term can be an issue. I have Penstemon grandiflorus growing here in the gravel drainfield around my house.  In a typical garden setting here it usually behaves as a biennial but because of the superior drainage in this material (wihich is on a slope) I had one plant survive 8 years.  This plant is native to Minnesota but you will never find it growing naturally except in gravelly or sandy areas.

Thanks for the thought about starting them in regular seed-starting mix.  When I look at the gravel or chicken grit I've purchased I can't imagine how anything would germinate in that, but that prejudice is probably because I'm an easterner and everything I see germinates in our rich, loamy, moist New England garden soil. I'm sure seeds in the arid west germinate in gravel all the time - how could they not? Maybe the key is to keep the gravel or grit wet?

Once the germination process has begun adequate moisture must be provided or the emerging seedlling will not survive. I imagine that in an arid climate a seed will not have enough moisture until the winter rains or snow hydrate the soil.  If you are concerned that your substrate is too porous to retain moisture long enought for germination to commence you could try mixing it with seedling media.  If you have enough seed you might try various ratios of grit to seed mixture to see which proportions are most successful.  I have found that the most difficult segment of establishing a plant is the transition from the cotyledon stage to a young plant with multiple leaves.  Damping off is a frequent problem with seedlings at the cotyledon stage.  Using some type of heating on the bottom of the seed flat/pot often will lessen the effect of damping off.

So water frequently enough so that adequate moisture is available the the critical time in your chosen porous planting media.

Another thing to remember is that in a moutainous area there are many microclimates such as the wet side of a mountain or in the rain shadow or altitude and the water needs of various species will reflect the availability of water in the area they evolved in.

[quote=Muggli]

I can't offer much advice on western species since I live in Minnesota.  I have started some seed of western species in regular seed starting mix and got them to germinate.  I then moved some of the seedlings into larger pots with a more suitable substrate.  The initial germination may not be too much of a problem but keeping them long term can be an issue. I have Penstemon grandiflorus growing here in the gravel drainfield around my house.  In a typical garden setting here it usually behaves as a biennial but because of the superior drainage in this material (wihich is on a slope) I had one plant survive 8 years.  This plant is native to Minnesota but you will never find it growing naturally except in gravelly or sandy areas.

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Interested to know what you use as the more suitable substrate in your larger pots. 

The substrate (Potting Mix) I use may vary depending on availability of the raw materials.  Generally it will be a grit or broken shards of stone that are not too large mixed with seed starting mix or a sandy based topsoil.  The proportions of each component may also vary according to the water needs of the plant as best I can determine through research of the habitat of the species in question.  I have been gardening for many years, but bear in mind that I am a neophyte when it comes to culturing these western species.

Have you thought about having an alpine house to shelter your plants from the excess moisture?

Good luck with your efforts, the genus has many extremely beautiful forms and colors in the various (huge numbers) of species in the western part of the continent.

When I look at the gravel or chicken grit I've purchased I can't imagine how anything would germinate in that

I am another rock gardener (and general gardener) from Minnesota.  It really is quite amazing how much water sand can hold (even near he surface) in a pot that doesn't have a continuous vertical column of soil (like a garden does).  The perched water table effect is dramatic with any similarly small sized aggregate, whether it is mineral or organic plant based.  Depending on the size of the chicken grit, seed could germinate in it.  Certainly it can in the turface.

I wash and re use pots for seeding, but I don't bleach or sterilize in any way.  I use what I deem to be correct media aggregates, but don't worry about sterilization or pasteurization.  I agree that germination and early growth is not very dependent on soil make up.  The only problem I have with damping off type diseases is with Townsendia seedlings.  Years ago, I devised a simple, no fungicide remedy.   For them, the pot is almost filled as normal with whatever rock garden substrate I am using.  Then a layer of just #1 chic grit that the seed is sown over, a bit more #1 grit and then covered with the normal layer of #2 grit.  Pots are watered, drained and put in a clear plastic bag until seed emergence.  This works incredibly well for me, and it might be another alternative for your western penstemons in your climate. 

Mike is right that our native Minnesota penstemons grow in sand (especially grandiflorus and gracilis) or gravel (especially albidus)..  Occasionally you will find them (and other rock garden plants) in tight crevices of rock outcrops filled with organic material.   

As most rock gardeners already realize, it is the combination of environmental factors that allow for a "foreign" plant to adapt, and it's often not just one recipe that works.  Change one ingredient and another(s) might need to be tweaked.  Heavier soils might be able to be compensated by keeping them drier, for instance.  In my clay based, dry garden, I have been growing P. grandiflorus for 20years.  Blooming in the second year, individual plants last about four or five years.

I am certainly not a man-in-the-know with western penstemons, although I have grown a few, but I will stick my neck out with a suggestion for you to ruminate. To transplant young seedlings into pots for westerners:

one-fifth regular potting mix

one-half pea gravel

the remainder equal parts of the turface, chic grit, oyster shells

Like any good gardener, you are going to learn to "feel" what is right for the soil.  You didn't say what size your chic grit is (turkey grit is #4).  My best advice is pay close attention to aggregate size and and proportion of organic matter in whatever mix you use, so you can record how different mixes react with different species.

Thanks, Muggli.  I fell in love with Penstemon last season when a plant from P. strictus seed I'd winter-sown in February 2017 actually bloomed.  I'd kind of forgotten I'd planted it there, and when I realized what it was I stood stunned and reflected on my good fortune at having grown Rocky Mountain Penstemon from seed in my regular rich New England garden soil.  Whether I'll see it again this May is anyone's guess.  After that experience, and also seeing a Penstemon 'Prairie Dusk' i'd planteed successfully over-winter and bloom in my garden, I was hooked. I thnk these experiences made me dream of the amazing blues of some of the western species.  I'm a NARGS member but don't have a rock garden so I know that's going to limit what I can grow.  I'd never heard the term 'alpine house' so I just looked it up and it looks interesting.

I just learned that there are different grades of chicken grit -- #1, #2 and #3?  I have #3 - the largest - but my local Agway is a quick drive from here and they have the other sizes.  What do you use? I guess it depends on the species?

[quote=RickR]

When I look at the gravel or chicken grit I've purchased I can't imagine how anything would germinate in that

I am another rock gardener (and general gardener) from Minnesota.  It really is quite amazing how much water sand can hold (even near he surface) in a pot that doesn't have a continuous vertical column of soil (like a garden does).  The perched water table effect is dramatic with any similarly small sized aggregate, whether it is mineral or organic plant based.  Depending on the size of the chicken grit, seed could germinate in it.  Certainly it can in the turface.

[/quote]

I wasn't familiar with the term 'perched water table' and looked it up and now I understand. So that effect can keep the soil moist.  I have chicken grit #3.  If that might be too large to hold water reliably or is otherwise not ideal for germination, should I get some #1 and #2, at least to experiment with?  Does the perched water table effect come into play for grit #3?  

[quote=RickR]

I wash and re use pots for seeding, but I don't bleach or sterilize in any way.  I use what I deem to be correct media aggregates, but don't worry about sterilization or pasteurization.  I agree that germination and early growth is not very dependent on soil make up.  The only problem I have with damping off type diseases is with Townsendia seedlings.  Years ago, I devised a simple, no fungicide remedy.   For them, the pot is almost filled as normal with whatever rock garden substrate I am using.  Then a layer of just #1 chic grit that the seed is sown over, a bit more #1 grit and then covered with the normal layer of #2 grit.  Pots are watered, drained and put in a clear plastic bag until seed emergence.  This works incredibly well for me, and it might be another alternative for your western penstemons in your climate. 

[/quote]

To confirm: you start out with some other substrate that you normally use, then #1 chic grit, then the seeds, then more #1, then a layer of #2 on top? Don't penstemon seeds want to be exposed to light, just on the surface?

[quote=RickR]

Mike is right that our native Minnesota penstemons grow in sand (especially grandiflorus and gracilis) or gravel (especially albidus)..  Occasionally you will find them (and other rock garden plants) in tight crevices of rock outcrops filled with organic material.   

As most rock gardeners already realize, it is the combination of environmental factors that allow for a "foreign" plant to adapt, and it's often not just one recipe that works.  Change one ingredient and another(s) might need to be tweaked.  Heavier soils might be able to be compensated by keeping them drier, for instance.  In my clay based, dry garden, I have been growing P. grandiflorus for 20years.  Blooming in the second year, individual plants last about four or five years.

I am certainly not a man-in-the-know with western penstemons, although I have grown a few, but I will stick my neck out with a suggestion for you to ruminate. To transplant young seedlings into pots for westerners:

one-fifth regular potting mix

one-half pea gravel

the remainder equal parts of the turface, chic grit, oyster shells

[/quote]

Thanks - I needed to hear that.  But I'm a little unclear: you're suggesting this as the mix for the pots for after the seeds have germinated?  I start the seeds out to germinate in a separate container, then transplant the young seedlings into this mix?

[quote=RickR]

Like any good gardener, you are going to learn to "feel" what is right for the soil.  You didn't say what size your chic grit is (turkey grit is #4).  My best advice is pay close attention to aggregate size and and proportion of organic matter in whatever mix you use, so you can record how different mixes react with different species.

[/quote]

Appreciate all this help.  Not only is growing penstemon new to me, but basic concepts of rock gardening are as well.  I have turkey grit, and chic grit #3, but Agway is a short drive away.

I do appreciate iquisitive minds. :)

I have never made a point to expose penstemon seed to light for germination.  Dr. Norman Deno was very methodical with his 10,000+ germination tests of thousands of species seeds.  Among his testings, his seed germination attempts included  both dark and light treatments.   Of the approximately 100 penstemon species he tested, only a few were found to require light. 

Dr. Deno's work can be downloaded free here:  https://www.nargs.org/forum/link-pdfs-dr-denos-seed-germination-books

Alternatively, an abreviation of the data in spread sheet form can be downloaded free at the bottom of the page here:

https://tomclothier.hort.net/page15.html

But he did not investigate if light could improve germination, and while many sites recommend surface sowing for all penstemon, real empirical data is lacking.  So maybe it would be better?  If you simply press the seed into the surface of sand or grit, then you will may also need to enclose the in a clear plastic bag.

#3 grit is fine for most applications, but purely as a seed bed it is too coarse in my opinion.  I usally keep #1, #2, #4 grits in my arsenal of soil media components.  As a seed bed like I relayed previously you could use just sand, or better yet, 2/3 sand 1/3 #3 grit.  You could still top with #3 grit, or nothing at all, if you wish.  Enclosed in a bag, there would certainly be enough moisture at the surface.  The difficulty is that penstemon are often erradic germinators, and you will need to remove the bag soon after your first seed emergences.  Likely, you would be hindering any further germinations without some kind of cover.

Of course, grit at the top would have no effect on a perched water table below.  However, if you mixed enough grit throughout the soil that significantly improves drainage, then yes, that would also affect the water table, making it lower.  If you undersand the perched water table, then you will understand how and why this experiment works:

http://www.srgc.net/forum/index.php?topic=8097.msg219668#msg219668

Yes, the mix I suggested is for transplanting seedlings into, after they have at least produced a pair of true leaves.  It's my preference to wait for two or three sets of leaves, but that's just me.  The mix seems incredibly lean: this is for the western penstemons in your climate.  You can always give them some extra fertilizer, but if you want them to be long lived, they need to have a sparse diet.

Congratulations with P. digitalis!   This species is an easier one.  P. digitalis is also one of the common imposter penstemons in seed exchanges.  It was one of the first penstemons I grew, (it was "supposedly" P. smallii),  but I enjoyed it very much.  Penstemons like Prairie Dusk and Husker's Red are hybrids selected for easy growing in regular garden soil.  There are a few others now that you can find in general nurseries and big box stores that have small flowers and mor succulent, often bluer foliage.  These will require better drainage and full sun, and will do better in leaner soil.

[quote=RickR]

I do appreciate iquisitive minds. :)

I have never made a point to expose penstemon seed to light for germination.  Dr. Norman Deno was very methodical with his 10,000+ germination tests of thousands of species seeds.  Among his testings, his seed germination attempts included  both dark and light treatments.   Of the approximately 100 penstemon species he tested, only a few were found to require light. 

Dr. Deno's work can be downloaded free here:  https://www.nargs.org/forum/link-pdfs-dr-denos-seed-germination-books

Alternatively, an abreviation of the data in spread sheet form can be downloaded free at the bottom of the page here:

https://tomclothier.hort.net/page15.html

But he did not investigate if light could improve germination, and while many sites recommend surface sowing for all penstemon, real empirical data is lacking.  So maybe it would be better?  If you simply press the seed into the surface of sand or grit, then you will may also need to enclose the in a clear plastic bag.

#3 grit is fine for most applications, but purely as a seed bed it is too coarse in my opinion.  I usally keep #1, #2, #4 grits in my arsenal of soil media components.  As a seed bed like I relayed previously you could use just sand, or better yet, 2/3 sand 1/3 #3 grit.  You could still top with #3 grit, or nothing at all, if you wish.  Enclosed in a bag, there would certainly be enough moisture at the surface.  The difficulty is that penstemon are often erradic germinators, and you will need to remove the bag soon after your first seed emergences.  Likely, you would be hindering any further germinations without some kind of cover.

Of course, grit at the top would have no effect on a perched water table below.  However, if you mixed enough grit throughout the soil that significantly improves drainage, then yes, that would also affect the water table, making it lower.  If you undersand the perched water table, then you will understand how and why this experiment works:

http://www.srgc.net/forum/index.php?topic=8097.msg219668#msg219668

Yes, the mix I suggested is for transplanting seedlings into, after they have at least produced a pair of true leaves.  It's my preference to wait for two or three sets of leaves, but that's just me.  The mix seems incredibly lean: this is for the western penstemons in your climate.  You can always give them some extra fertilizer, but if you want them to be long lived, they need to have a sparse diet.

Congratulations with P. digitalis!   This species is an easier one.  P. digitalis is also one of the common imposter penstemons in seed exchanges.  It was one of the first penstemons I grew, (it was "supposedly" P. smallii),  but I enjoyed it very much.  Penstemons like Prairie Dusk and Husker's Red are hybrids selected for easy growing in regular garden soil.  There are a few others now that you can find in general nurseries and big box stores that have small flowers and mor succulent, often bluer foliage.  These will require better drainage and full sun, and will do better in leaner soil.

[/quote]

in a seed bed of just sand, or two-thirds sand and one-thirds #3 grit

I was suggesting this as a layer for initial germination that is on top of a mix  containing some nutrition.  I've never needed to do this for any penstemons, myself.  I always direct seeded into a uniform well drained mix.  I would only do it if I think I will encounter a disease problem.  I mentioned this method because of your wetter climate, for the westerners.

Some will transplant seedlings at the first set of true leaves.  Myself, I lke to wait until 2 or three sets; I think I get better survival.  Sometimes if there is only one or a few seedlings in a pot, I won't transplant until the following year.

I 've always wondered about the tube sand: what it actually is.  Since it is only meant to be sold as weight for your vehicles in winter (at least here in Minnesota), is it really JUST sand, or ...?  I dunno.  Where does all the sand that street cleners sweep up go? I think it is safer to use the bags of sand labeled as play sand or sand for mixing with cement.  Or the stuff in bulk at a landscape place.  At least with these, you know for sure there won't be any  winter salt contaminates.

People talk about sharp sand.  The best quality of truly sharp sand  is pool filter sand.  Very angular, and with ABSOLUTELY no fines.  I have used it, but don't see any need for it.  What you do want is as coarse sand as you can find that has as little fine particles in it as possible.  (That's where the "washed" sand will help.)  Isn't that the same as pool filter sand? No.  You're not worried about having all the exact same size aggregate that pool filter sand has.  In fact you want all different sizes, minus the very fine.  (That's why you add pea gravel, or other grit sizes.) 

Sharp (pool filter) sand and Builder's sand

Again, at the seedling stage, what alpines grow in isn't as important.  In fact, some growers purposely grow seedlings in richer soil to give them a jump start.  But they always get put into the proper mix eventually.

Well, this evening I took my first halting steps into the world of sowing penstemon seed in pots. I have no idea if what I did will work but I planted seed in five of the 15 plastic pots I have, which are 7" tall and 6" in diameter.  Since I only have a single bag of pea gravel, I filled the bottom half of each pot with a mixture of pea gravel and something called Hydroton, "expanded clay pebbles" that I bought at a hydroponics store.  For the next layer, maybe a quarter of the total, I mixed regular potting soil and #2 chicken grit.  Then for the last quarter, I mixed 50% turface and 50% sand and added that.  I then planted the seeds directly on top of that, covering the seeds gently with a sprinkling of that mix.  Tomorrow I'll water what's in the pots and place them outside. 

I planted Penstemon albertinus, ovatus, richardsonii, grandiflorus and cobaea.  

I'm not sure I have the patience to germinate the seed in one container and then transplant the seedlings into another.

Any thoughts about whether what I did has some chance of working?  If not, I have 10 more pots in which to make even more interesting mistakes.

When I plant seed, especially from seed exchanges, most of the time I use 3 or 4 inch pots.  It's not uncommon that seed doesn't come up (for a variety of reasons), but sometimes I will get a plethora, and sometimes just 1 to three.  If I just have a few, they might stay in the pot untill the following spring when I transplant.  With bigger pots, you just need to be more careful about overwatering.

I may have confused you when I explained my layering with my townsendia seeds.  Layering of different types of soils and especial vastly different size aggregates can be problematic for plant growth, if you are expecting roots to cross over into adjacent layers.  Unless a layer is "better" than the layer a root is currently in, the root just won't go there.  On the other hand, a gradual change over of one kind of soil/aggregate size to another is perfectly fine.  Roots have no problem penetrating to whatever depth is healthy for them.

Almost all rock and alpine plants like their "necks" very well drained, with roots penetrating deeper into moister soils.  The crown of the plant (the neck) is susceptible to rot, whereas plants native to moister climates without dry winds have adapted to become rot resistant.  This is why rock and alpine gardens don't use an organic mulch (like leaves or barks) that retains moisture at the surface.  Rather, rock gardens have rock mulches that dry out quickly.  So this was the exact reason why I modified my townsendia seeding: to keep the susceptible crown of the plant (where the seed is) dry, while still allowing the roots to grow down to where they can obtain moisture and nutrients.

Notice too, that my townsendia example is exactly the opposite of yours. Mine is larger aggregates on top, with smaller aggregates below.  This is how nature works, too.  You have small aggregates on top, with large aggregates below. 

So what I would recommend is mix all those ingredients together at approximatedly the same ratios as you have stated (it's not rocket science), and fill the pots with the same stuff, top to bottom.  It's going to be very rocky; your penstemon will love it!  If you would like to still have a few millimeters of sand on top or a top dressing of grit, that would be fine.

By the way, Penstemon hirsutus var. pygmaeus is a stalwart rock garden plant, and a blooming machine.  Being  the species hirsutus, it's already adapted to the east and will do great with no special care in your climate. 

ok, thanks for this.  I did misunderstand so I'll just start over on those five pots and mix everything together rather than layering.

btw, I notice that in his book Growing Penstemons Dale Lindgren recommends for a potting mix just perlite and vermiculite, with the possible addition of sand.  In his book Robert Nold suggests something similar: "equal parts perlite, vermiculite, and sand," mentioning later in the paragraph that grit is good as well. 

I was surprised at their focus on perlite/vermiculite; I haven't used those at all except the small amounts that's already in the 20% potting mix I used.  Maybe since I'm in a much more moist environment perlite/vermiculite is less necessary?

Thanks for the tip about Penstemon hirsutus var. pygmaeus.

I would have redone those first five pots if I had not already seeded them.  How are you going to retrieve the seeds?   It's your call ....

Maybe since I'm in a much more moist environment perlite/vermiculite is less necessary?

Actually just the opposite: the perlite and vermiculite provide more air spaces in the growing media (while not adding nutrients).  This becomes more important in place with higher rainfall and more humidity.  Think about how much more dry a western soil is, compared to yours in Massachusetts.

Bob Nold understands soil physics better than most!

Regarding P. hirsutus var. pygmaeus, the seed is always available in our seed exchange.  Because it is a seed grown dwarf, you may find size variation in the seedlings.  you might want to discard the largest, fastest growing one(s) if you want the keep your stock the most dwarf.

I did redo those first five pots.  My plan was to take a spatula and scrape off the first inch of mix at the top of the pot and put that in another pot, then mix everything up, then put the inch back on at the top.  But I didn't.  I just mixed everything up - seeds at the top and all - and then put fresh new seed at the top.  Thank you to seed exchanges for making that possible. 

Maybe 20 years from now the old buried seed will make its way to the top and surprise the heck out of me and germinate.

Thanks for the thoughts about perlite and vermiculite.

btw, why is there a danger of overwatering with large pots?  I did use the 6" pots.

Here are the penstemon species I planted:

• P.  albertinus
• P.  barrettiae
• P.  cardinalis
• P.  cardwellii
• P.  cobaea
• P.  eatonii
• P.  grandiflorus
• P.  ovatus
• P.  procerus
• P.  richardsonii
• P.  rostiflorus
• P.  serralatus
• P.  smallii
• P.  'Sunburst Ruby'
• P.  venustus
   

...with (I think) many more to come.

That's quite a list!

It's easy to overwater large pots because they hold a lot more water and take longer to dry out.  People have these unfounded tendenciesto kill plants with love (and extra water), and put watering on a schedule.  Both are never good things.  If you only water when they need it, you will do fine.  Just don't water every Sunday or somesuch.  Timing will change according to many variables, and of course, seeds actually use very little water.

I am wondering if it would be good to put some window screening over my pots outside, to keep the seeds from blowing away and maybe keep critters and birds away from the seeds as well as the seedlings once they emerge.  Is some kind of covering that like standard protocol for pots of seeds left outside in the winter?  I have a large roll of window screen which I could cut into pieces, but I'm not sure how I'd anchor it around the top of the pots.  Maybe some thin wire.

RickR, I want to thank you for the help with this back in February and give you an update for this batch of seeds I started in large pots.  (This is separate from the seeds I started in milk jugs and potting soil that I just posted about.) For this batch, I used a mixture pretty similar to what you'd suggested: pea gravel, chicken grit, turface, sand, and a touch of seed starting mix.  I'm pretty happy with the results so far.  They're all growing very slowly, and I still have only cotyledons, and for some species I have only one or two seedlings in the pot, but it's a start.  I have: P. fruticosus, P. virens (many seedlings), P. grandiflorus, a P. strictus x P. barbatus hybrid (many), P. gormanii (many), P. richardsonii, P. ovatus, P. cardwellii, P. digitalis, P. venustus, P. tenuis, P. virgatus, P. newberryi, P. albidus, P. rupicola, P. eatonii, P. superbus.  Hopefully soon I'll get some true leaves, and then who knows what time will bring.