Type of potting material for planting penstemon seed

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sf2bos2prov
Title: Member
Joined: 2018-10-04
Type of potting material for planting penstemon seed

Here in Boston, over the next week I'm going to start seed for various species of Penstemon in pots which I'll cover with window screen and leave outside. To prepare, I went to Agway and bought 50 lbs of pea gravel, 50 lbs of Turface, 10 lbs. chicken grit (maybe I should get turkey grit instead?) and 10 lbs crushed oyster shells.  I also have regular potting mix that I would use for my regular non-Penstemon east coast species.

Can someone suggest what combination of these materials I should use to start my seeds in? I have some east coast penstemon (P. laevigatus, canescens, pallidus, calycosus), some midwesterners (gracilis, cobaea, grandiflorus) and a good number of some of the dryland westerners that I know I'm taking a serious risk with. I think I can plant the easteners in regular potting soil, but the others will need some combination of the others.  Thanks for any help.

Muggli
Title: Member
Joined: 2011-12-10

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.

sf2bos2prov
Title: Member
Joined: 2018-10-04

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?

Near Boston, MA, zone 6b.  Average annual rainfall = 44 inches

Muggli
Title: Member
Joined: 2011-12-10

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.

sf2bos2prov
Title: Member
Joined: 2018-10-04

[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.

[/quote]

 

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

Near Boston, MA, zone 6b.  Average annual rainfall = 44 inches

Muggli
Title: Member
Joined: 2011-12-10

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.

RickR
Title: Moderator
Joined: 2009-09-21

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.

 

Rick Rodich    zone 4a.    Annual precipitation ~24 inches near Minneapolis, Minnesota, USA

sf2bos2prov
Title: Member
Joined: 2018-10-04

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?

Near Boston, MA, zone 6b.  Average annual rainfall = 44 inches

sf2bos2prov
Title: Member
Joined: 2018-10-04

[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.

Near Boston, MA, zone 6b.  Average annual rainfall = 44 inches

RickR
Title: Moderator
Joined: 2009-09-21

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.

 

 

Rick Rodich    zone 4a.    Annual precipitation ~24 inches near Minneapolis, Minnesota, USA

sf2bos2prov
Title: Member
Joined: 2018-10-04
Interesting about the issue about whether pent seeds want light or darkness.  I've consulted Tom Clothier's pages before for other species, but haven't looked at them for Penstemon.  
 
So your suggestion is to sow the seeds (at least the westerners, and maybe the northwesterners and midwesterners as well?) in a seed bed of just sand, or two-thirds sand and one-thirds #3 grit. After a couple of true leaves appear, then transplant into the mix you mentioned before? I have a bag of Sakrete tube sand - will that be ok for the seed germination? Is there a special garden-quality sand that is better for this?
 
Before I started thinking this all through, I did winter-sow in gallon-sized translucent plastic jugs seed of various penstemon species into the same potting soil (Foxfarm Happy Frog: Aged forest products, sphagnum peat moss, perlite, earthworm castings, bat guano, humic acid, oyster shell, dolomite) that I use for my non-Penstemon seeds.  Now I understand that many of the Penstemon will not appreciate the nutrients and water-rentative capacity of this mix.  Well, I'll let these go and see what happens with them, but I'm planning to start a completely new batch with this new plan since I have plenty of seed.
 

[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]

Near Boston, MA, zone 6b.  Average annual rainfall = 44 inches

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