Salpiglossis Techniques and Trials

My last post, (which was surprisingly this past February) proves not only how busy I’ve been, but how time can fly by. First, just so you know – I’m mostly posting to my Instagram account lately (mostly everyday). So if you need more updates than my blog offers, follow me at @matt_mattus on Instagram and see what’s happening in the garden, greenhouse and sometimes in the kitchen.

My 2022 trials we as obsessive as usual, but perhaps even mores this year as we were honored to have our garden included as a Garden Conservancy Open Days garden in May. If any of you have participated in this event, you know how time consuming preparing ones garden for a tour can be. OK, I know it’s already October, but even though our tour was in May, it was well attended (sold out in 24 hours) and for about a month and a half after that, we were just wiped out. Then, summer hit full-on, with drought, heat and then COVID for both of us (we’re fine, just mild but exhausting symptoms) and the one garden client we have required much attention for a big photoshoot – more about that later. Anyway, time flies, and I don’t think that I’ve ever skipped so many months posting to this blog. Maybe blogging itself is changing as well, in a world of faster social media like Instagram? Please let me know you still read and follow this, or if you prefer a different medium (Podcast, video, something else), as that will help me decide where to share.

I’ll bet that very few people grow, if even care about the old fashioned annual flower called Salpiglossis or bearded Tongue, but to follow through from my last post, this year I decided to try various techniques and methods, most of which challenged what one will find on the internet or even in books and seed catalogs. Cultural information for more uncommon annuals is often incorrect – I really don’t know why other than this information is often second or third-hand. I would bet that many garden writers research via the internet, Google search or via the latest books, and to be fair, many freelancers are on a tight deadline. I’m really not trying to be critical here, but instead – simply honest. My guess here is that some cultural information is just passed along via respectable sources (university sites, seed companies and in gardening books) but rarely are they challenged or researched deeply. My findings may still be incorrect, but after three years, I am getting extraordinary results with a few annuals, and this Salpiglossis trial is confirming some surprising findings.

Briefly, Salpiglossis information from seed to flowers often starts with germination advice that is contradictory. Germinate dark, surface sown, sow seed 1/4 inch deep, seed needs light or complete darkness to germinate. For years I used to follow directions from a very trusted book on raising annuals – I covered surface sown seed with tinfoil, kept trays warm until seeds germinated. While I don’t know where this information originated, it may have come from early seed collectors who noted that in its native habitat, Salpiglossis sinuata grows in a unique coastal climate where the marine air is cool, frequent fog and overcast in winter, but the seed drops down onto a rocky surface where it is shaded. I should note that my research is certainly flawed, I usually try to look backwards through history to see where a plant is native to, I make notes about the climate there, and how it relates to the plants natural cycles. Salpiglossis is unique in this case. Still, there is no excuse for such contradiction when it comes to germination advice – and some seed packets from large seed companies offer contradicting information printed on the same packet in different locations.

The above image shows my reward for following directions, both from two old books (reviewed in my previous post). I couldn’t believe that my tiny seedlings would grow -with great care, but not all that much effort – into what the books once promised – 4-5 foot tall plants, some as tall as 6 feet tall. If you’ve ever tried growing salpiglossis in your flower beds from seedlings bought at nurseries, you know how unusual this is. I wanted to figure out why nursery plants often topped out at 1.5 feet tall – maybe 24″, and what were we doing wrong.

I used a number of sources for both seed and cultural advice, but the 2021-22 seed catalogs offered only a few varieties of salpiglossis. It seems the few breeders only introduce a strain that is interesting every few years, and most seed companies default back to the old standards. This is understandable as so few of us grow salpiglossis. It’s not a great cut-flower, and a good majority of home gardeners don’t even know what it is, let alone have actually seen a plant in bloom before. Thumbnail photos are often misleading, and many might just write it off as another petunia-look-alike (it is released, however, as salpiglossis is organized within Solanaceae, along with petunias and tomatoes).

I should also add that while I had success growing salpiglossis following the cultural advice often found on-line or in books (surface sow, but keep trays in complete darkness until germination), I always found that even if I catch the seedlings just as they have germinated, they would still be too elongated and never seemed to recover. Not to mention that I always wondered why such advice existed, as it just never made sense. I found that the very old books (19th century) often suggested covering the seed lightly, but my mind was changed once I started downloading professional grower guides supplied by the major seed suppliers (where seed catalogs get their seed from). These guides are written for commercial growers – often plug growers or wholesale nurseries who depend on raising healthy crops of bedding plants. While often not helpful for home growers, as these can be complex or offer information such as feeding schedules that are in code, or parts per million, they do offer some valuable bits of advice, one of which was soil depth for seed sowing which was 1/8 – 1.4″ deep. Not surface sown.

I germinated all 5 packets of seeds indoors, between January and early March to see if timing made a difference. seed pots and flats where sown thinly, covered with fine vermiculite at about 1/8 inch deep, and set under high intensity, full-spectrum LED lights in a spare bedroom. The warm, indoor temperatures were beneficial and it’s a method I’ll do again as it worked much better than heating mats outdoors for me (maybe because the temperature differential from day to night was measurable, and not consistent.).

Professional grower sheets provided another clue, and that is as with snapdragons and sometimes pansies, the seed trays and pots were allowed to dry out between watering. This is a critical step for salpiglossis, as they tend to be weak rooted, and dry medium forces roots to go searching for water, and thus, nutrients. Drying out between watering to a point of slight wilt also stimulated seedlings to grow denser and produced stockier seedlings.

Fertilizer was also key, as salpiglossis has some demands and sensitivity as with petunias and snaps. I used the recommended amount of a Cal-Mag feed (you can find it under the Peters or Jack’s Brand on Amazon sold as Petunia Feed. It’s hard to find at retail offered in small amounts, as most sources only offer Cal Mag in 50lb bags for professional growers. It’s a must for growing snapdragons, pansies and petunias). You an find more info about the benefits of using a cal-mag feed here https://www.gardenmyths.com/cal-mag-plants/ and you can read here https://www.greenhousegrower.com/crops/petunia-finished-production-tips/ about why snapdragons and petunia seedlings require cal-mag feeds.especially if you use an acidic potting mix (peat based) or coir based. If you’ve ever tried to grow snaps and found the leaves starting to yellow while still very young, this is probably why. All the Miracle-Gro in the world won’t turn them green. (note: Not all flowers or veg need additional calcium or magnesium, and while these elements aren’t added to regular fertilizers, and not always needed, I’d avoid using home made solutions (such as Epsom salts and eggshells). Epsom may work if you can measure it precisely, but it still will need calcium to work well, and egg shells aren’t a good choice for seedlings due to the year, or so, required for eggshells to decay and convert to usable calcium).

Another good tip came with when and how to transplant. Salpiglossis dislike root disturbance or better yet, root restriction. They like a free root run, and seedlings will sulk and bolt if pots become root bound, as in nursery 6 packs – one of the main reasons why I think nursery plants in small modules are often don’t perform well. I can understand why nurseries grow their annuals this way, it’s easier to grow all of ones crops the same way, but unlike their kin snapdragons or petunias, where extra fertilizer applied to even tiny pots, will still produce strong, yet root bound, seedlings. One benefit of keeping salpiglossis in small modules rootbound, is that they’ll bloom younger, which obviously has its benefits as most consumers want to buy a plant in bloom, but buying a salpiglossis 6 pack with flower buds will do you no favors. They’ll bloom for a few weeks, and maybe reach a foot or so tall, but then that’s it. I wanted to see if I could produce those 5 foot tall plants with dozens and dozens of flowers that the old gardening books promised. As you’ll see, I did, but it took the luxury of greenhouse space, and daily coddling.

I potted young seedlings up into larger pots as soon as they formed their first or second pair of true leaves. The older texts suggested a final pot size of 9″, so I began transferring into 3″ and 4″ pots at first, so that I could easily dry out the pots between watering, but then moved them up to 6 and 8″ pots. I thought that these might be the final size, but plants began to grow so large that I decided to upgrade 12 of them to 12 and 14″ deep clay long-toms. I used Pro-Mix BX as my primary medium, and continued a seeking Cal Mag feed if I could dry the pots out slightly (this depended on the weather). I quickly learned that the larger the pot, the better the results, but what surprised me was that while plants were growing tall and branching well in the largest pots, in the smaller ones, and especially those seedlings that I kept in 2″ 6 packs, that were root bound and fed the same diet, they began to form flower buds and bloom early at 9″ tall. These looked more like the typical seedling I would find at my local garden center.

Clearly the best results came from plants in the largest pots. I did pot some containers with 3 seedlings, but these didn’t grow as large as those did in the 14″ pots. Kept in the greenhouse, the leaves grew lush and large, requiring 5′ bamboo stakes one the central stem began to extend. I pinched some, which was advised, but found that the most elegant look came with those that were not pinched, and it seemed, just as many blooms. I relocated some plants outdoors around June 1, but that subjected them to an infestation of leaf miner, that ruined many leaved with their winding paths, just like spinach that was planted nearby. I removed most of the leaved, and moved all plants back underclass where the seemed to not mind the high heat on sunny days (near 100° F) if watered daily.