Propagation - Tips from a Pro

Once a month I help out our local CNPS chapter, which is Santa Cruz, by volunteering with the plant propagation group.

It’s hardly a selfless act. I meet very nice people interested in native plants, I learn about propagating all kinds of plant materials, and I get lots of free practice. Plus – I get to call it, “volunteering!” Ha!

Last month, I worked with one of the two propagation group co-ordinators, Denise Polk, potting up some seedlings in one of the beautiful huge new greenhouses at Suncrest Nurseries, a wholesale nursery in Watsonville that kindly donates space and material to CNPS for the purpose, and also looks after the plants between our visits.

I confess I don’t remember what we were potting up. They had a long name I didn’t know. The other good thing about volunteering is I learn more plants. (Except when I don’t .)

Denise is a professional horticulturist, and manages various greenhouses at U.C. Santa Cruz. I asked her if I could pick her brains regarding propagating seeds and cuttings. I came to the meeting with malice aforethought, and a voice recorder. Denise kindly agreed to give advice on record, and as we potted, we prattled. (Sorry. I have a hopeless addiction to alliteration.)

I was going to summarize brief bullet points but decided to just provide direct quotes, so this gets a little long, but I hope is of interest (to those with an interest anyway).

I told Denise how I had planted seeds from gathered foothill needlegrass (Nassella lepida), zauschneria (probably Z. canis) , and mimulus (Probably M. Aurianticus); as well as seeds from nursery stock penstemons (P. heterophyllus “Margarita BOP” and P. azureus), all in flats and plugs. I also tried planting cuttings from nursery stock mimulus (M. “Trish” – salmon colored, and M Eleanor, pale gold – and wonderful lush greenery too).

Jackie: “I put them in equal parts organic potting mix, coarse sand, and Perlite.”

Denise: “That sounds fine – as long as the mixture is pretty loose, you don’t want it to be too soggy. You want good aeration, so that should be OK. With mimulus what is more important is the condition of the stem itself, whether it’s really soft new growth or whether it’s woody and hard, those are extremes you want to avoid. You want to use new growth but that’s firmed up a little. It doesn’t bend really easily but it’s got a bit of a bend to it. Usually if it’s too soft it rots and if too hard it’s not inclined to root at all. About 4 inches is a general size guideline. Loose draining soil is particularly important for cuttings. We use half perlite and half peat moss. We’ve also got bottom heat and a mist system.”

Mine had bottom cold and a plastic wrap so well concocted with string and duct tape and battened to a shed wall that I couldn’t get inside to water. They were also on the north side of the house, and in the shade.

Denise: “I think the fact that there is no sun is probably a good thing. You want to protect your cuttings from desiccating. Especially if you don’t have a mist system that’s always putting moisture on the foliage. So definitely I think a shady area is important.

If it’s a little too cool that may not a problem. It might take longer. Usually it will take 2-3 months without bottom heat. So - you’ve got to keep them living. Sun is too much stress for them. And you’ve got to keep a lot of even moisture on them. But not soggy or the stem will rot. And it’s important to keep some kind of humidity or coolness around the leaves to keep them viable.”

Jackie: “They all just started to just fall over. I’m not sure I got them watered all the way down.”

Denise: “In the future make sure the soil is already premoistened. Then stick your cuttings in. Then if you can put some kind of tarping over them to keep the moisture in. And it’s good if you’re in the shade, because if they’re in the sun and tarped they get way too hot.”

I asked how frequently to water so they stay moist.

Denise: “You have to play around with that, depending on the soil mix, how moist the soil was to begin with, how much sun and shade. As long as the soil is damp, that’s all it needs. It’s not like you’re watering a plant that’s got roots to take up the water.”

No roots to take up the water! Of course! Sometimes the obvious eludes us. Or me anyway.

Jackie: “So I gave up on the cuttings. Then I was more concerned that the seeds weren’t getting enough warmth and light to germinate. So far only one seed has germinated!”

Denise: “Some things will come up right away and some things will wait until the environmental conditions are right.”

Jackie: “I moved them up to where they get morning sun and afternoon shade.”

[note: since then I’ve had lots of grass come up and quite a number of tiny zauschneria.]

Denise: “That sounds good for the seeds. A lot of plants would be coming up in full sun, so that isn’t something you need to be too concerned about.”

Jackie: “I don’t have a plastic covering on them yet – should I do that?”

Denise: I don’t for seeds. Just for the cuttings. I’ve had the problem of the birds eating all the seeds. So you notice over here they’ve got bird netting on all their seed flats. There’s always a question, if the seed was even viable to begin with you know. What month did you sow the seeds?’

(It was Hogmanay - that’s the last day of the year, to a Scot.)

Denise: “That’s kind of early and late at the same time. It’s good to get them in the ground in time for the first rains. If we had gotten rain in October. So if you’re sowing seeds at home for native stuff it’s really good to have it out by then. It’s much better for the cycle, so that then they can get their roots down and get the top growth going so that they’re in sync and if they’re actually in the ground they’ll be well established by the time the rains stop. If you start seeds at home late in the season they’re going to have a harder time adapting, if you’re going to transplant them straight into the yard without giving them supplemental irrigation. A lot of people people feel better, if they know they want a plant in a particular spot, to directly sow those seeds right there.”

Jackie: “I did some of that too – I sowed in the ground in a sunny south garden area. (about 20’ X 10’) Penstemons, sulphur buckwheat.” I explained how I did the preparation – water. Wait. Weed. Repeat 3 times. After I broadcast the seeds – which I did with no great science at all – I covered it all with floating row cover. “Now it’s kind of sticking on the ground when I water. Not sure if that’s a bad thing. I’m watering about every other day – we have sandy soil, the water runs right through. Is that OK?”

Denise: “I don’t know – you’d have to keep checking your soil to see what the moisture is like. I haven’t done floating row covers.”

Jackie: “It look like thin interlining, that stuff dressmakers use.”

Denise: Maybe hoops or bend wire or something to keep it up off the ground.

Jackie: “like with pies.”

Denise: “Yeah that’s right”

(In fact I decided that the sticking isn’t really a problem. It’s only when I water.)

Jacke: “Well, you can say, ‘check the soil to see if it’s moist enough,’ because you have judgment. I have no judgment. I have a moisture meter. Can you over water them?”

Denise: “One could if it flooded the area – that happened to me one year – we had such heavy rain all my seeds washed away. That was the year after the birds ate all my seeds.”

(Talk intermingled with much mirth of mutual empathy.)

Jackie: “Well I’m glad I’m not the only one to have disasters.”

Denise: “Then there was the year when I direct sowed and everything came up beautifully and we had the midwinter drought and I didn’t give them any extra water. So I’ve given up. I have such a small yard that I don’t need to direct sow. I can just do transplanting. And plus sometimes I don’t know honestly which are the weeds and which are the seeds until I have some experience with them later and so that’s another problem.

“With direct sowing, the idea is you get the timing down better. With transplanted seeds by the time you get them into the ground you’re usually running a little late. Of course this year we’ve had so little rain things may be coming up later anyway. [or sooner!]

“But in terms of how wet, you know so much depends on the soil. But if after it’s watered in, the soil is wet at least a foot down or so, then the seed can sense that there is moisture down there and put its root down. It has mechanisms for knowing, and if there’s not enough moisture then it won’t germinate.”

Jackie: “I got a moisture meter and I tested it this morning. It was dry in the top two to three inches and then farther down it was moister, in the middle range.”

Denise: “When I sow seeds in flats or in a pot, I do want to make sure that there is still moisture on the top. Because you also don’t want want the seed to start to get some water, think there’s enough, start to germinate, and then have it go dry – then it just kills the germinating embryo, and it’ll stop the whole process.”

So I’ll stop now and just go check those seedlings…

Wow! The first tiny tiny seedlings in the penstemon flats - just two! (I wonder if they’re penstemons?)


joey said…
Thanks for sharing the hot tips!
Town Mouse said…
Very impressive! We should repost that one in October...

thanks so much!
Isn't seeding fun. Every morning I take the dogs and a cup of coffee on the rounds to see what's germinated and what hasn't. Looking forward to seeing how your penstemons do. Great Post.