I’ve already sown countless seeds this year, with still more to go, and many seedlings are taking off in the warm, bright environment of my new greenhouse. Greenhouse growing is a new experience for me, and I talked all about it and shared seed starting updates with my friend Craig LeHoullier, a frequent guest on the podcast and an expert seed starter and tomato grower.
Craig lives in Hendersonville, North Carolina, and has been gardening since 1981. He literally wrote the book on growing tomatoes, “Epic Tomatoes: How to Select and Grow the Best Varieties of All Time.” He also penned the gardening book “Growing Vegetables in Straw Bales,” plus he’s the tomato adviser to the Seed Savers Exchange and a co-leader of the Dwarf Tomato Project. Together, Craig and I co-lead the Online Gardening Academy Course Growing Epic Tomatoes.
At this time of year, I’m thinking about tomato seedlings and the dense planting technique that Craig advocates. That’s why I thought now would be the perfect time for us to catch up and to welcome Craig back to the podcast.
Craig and his wife, Sue, caught COVID in January, so this year has gotten off to a slow start for them. Craig is stepping back from traveling to give talks and presentations, but he’s still as busy as ever growing and experimenting.
Craig’s always busy, but he anticipates this season will be “different busy.”
Craig has a huge seed collection, and he gets a lot of emails requesting seeds of different varieties. In 2022 and 2023 combined, he received 300 messages requesting seeds, and many of the requestors asked for five or 10 samples each. It takes a long time to locate those seeds and label packages for mailing, but he’s finally done with that activity for the year.
“I’ve created this wild set of tomato family trees, and I always try to go back as far as I can to get something that’s truest to what was sent to me,” he says. “So I’ve got a flat of the oldies that are going to take probably not three to four days to germinate, but maybe eight, 10 or 12 days, if they germinate at all.”
He’s growing many more plants this year than he originally planned on because of some local opportunities that opened up for him.
“Because COVID is largely over, now all of a sudden Hendersonville is trying to tap into me as a resource,” he says.
He’s scheduled to do a number of local talks to neighborhood garden clubs and other groups, and a veterans healing farm down the street from him is letting him use their greenhouse to plant 120 tomato plants there.
And that’s not all.
“There’s a local farm that wants to do a dwarf tomato trial, so I brought them 10 seeds each of 20 varieties,” he says.
Craig and I worked closely together for two years on our Growing Epic Tomatoes course, but he points out that now we’ll be working more in parallel and occasionally touching base.
He’s also appearing over Zoom for different groups, including one in Texas, but he says he turned down an offer to travel to Arizona because he’s officially a “homebody” now and will no longer travel for events.
Of his new plans he says, it’s a “different type of music, maybe, but still lots of music.”
One of the things I love about gardening is that no two years are the same, let alone no two days. I applaud Craig for exploring new ways to keep his gardening life interesting.
How Having a Greenhouse Has Changed My Approach to Gardening
Craig is expecting temperatures to fall to 25°F in his garden with 20-mph winds, making for extreme windchill temperatures. This is coming after star magnolias, saucer magnolias and daffodils have already bloomed.
“The plants have not yet adjusted to what the weather patterns are doing, and it always makes me a little bit sad to see something beautifully filled out and then know that it’s going be brown,” he says.
As I get accustomed to raising seedlings in my Yoderbilt greenhouse for the first time, as all greenhouses are notorious for, I’m struggling with keeping the space warm overnight. I’ve brought in propane heaters for supplemental heat to protect my tomato, pepper and cool-season crop seedlings as the temperature dips to 27° F. I am working on insulating the greenhouse and am looking forward to that being done so I can get my benches, work tables and seed trays where I want them.
Craig poses an interesting question: How is this greenhouse changing my gardening approach, and how am I working it into my normal planting and growing patterns?
I admit there is a big learning curve to seed starting in a greenhouse. I have been seed starting indoors under lights for years, and I am very confident in doing that. Now I see the greenhouse has a complement to what I am doing indoors.
I enjoy the controlled environment inside, including in July when I can start fall cool-season crops indoors — something I couldn’t do in a greenhouse.
I’m still seed starting under grow lights, and then I get them out into the greenhouse as quickly as I can. Inside the greenhouse is 70% of full sunlight, so I know my seedlings won’t be cooked in there this time of year.
The seedlings are blowing up in a beautiful way so it’s hard not to go out there about 20 times a day. I really do love having this greenhouse. It’s everything I had hoped for and more. And that’s saying a lot!
Typically, I start my peppers around the first of the year because they take a lot longer to germinate than most seeds. However, they tend to just sit there. By mid-April, all I have are seedlings that are just an inch or two tall, and that’s not very impressive when I hold my annual seedling sale. They take off once it gets hot, but it’s awkward to explain that while handing off these tiny things.
But this year, in my greenhouse, those pepper plants are gorgeous already. Fingers crossed, it will be the same case with my tomato plants. It is quite a dramatic difference, from seeing how my plants perform under grow lights to seeing them perform in a greenhouse.
Managing Pests and Heat
When pests find a warm greenhouse, they want to stay and make babies. My strategy is to use rosemary oil from Earth’s Ally, a botanical oil that smells good and effectively coats soft-bodied pests. I may bring in some beneficial insects from an insectary if beneficials don’t show up on their own.
Craig says he’ll be watching from not too far away, vicariously greenhouse managing through what I’m sharing about it.
One concern Craig raises is what a changing climate will mean for tomato growers.
“If areas of the country do become too hot to grow tomatoes well outside because of pollen death, using indoor planting is going to be one of the things that people are going to have to figure out,” he says.
This includes cooling plants down so they’re running at an optimum temperature, he explains.
I wonder already how I will cool my greenhouse this summer. When it’s 46° outside, the greenhouse reaches 90° or more. I have windows I can open and a back vent to pull hot air out, but what’s it going to be like when the outdoor temperature is 90°?
Growing 50-Plus Tomato Varieties
Last year I had 25 varieties of tomatoes for my plant sale, and this year I’m up to 54, including 18 dwarf varieties for the first time. If I am ever going to cut back, this certainly isn’t the year for it.
However, I won’t have as much room to grow tomatoes in my garden this year because where I had livestock panels, grow bags and straw bales, new flower beds are going in around the entire interior perimeter of the garden. I have 12 bags of Soil³ right now sitting in my driveway that are going to go into those beds.
I can’t resist planting one of everything, so I know I’ll grow at least 54 tomato plants in my garden — and more than one of my favorite varieties, like Cherokee Purple, Black Krim and Sun Gold.
Craig originally planned on growing enough plants for his own garden, which he intends to re-orient this year. But between the veteran’s farm hoop house and the other farm that wants to do the dwarf tomato trial, he can now use those remote locations to grow some of the varieties he wanted to raise for seed saving, and he can dedicate his own yard to nothing but research and development.
“I expected to really close things down, and now things have kind of been blown way open for me again,” Craig says.
He also plans to grow melons again for the first time in many years. He will grow them in straw bales and see how they perform. He already knows that tomatoes do really well in straw bales in his climate. He’ll use 4-foot-tall tomato cages to keep the melons from sprawling on the ground. He plans to grow Minnesota Midgets and old varieties like Eden’s Gem and Jenny Lind.
“Some of those older varieties are just really, really tasty,” Craig says. “It’s just that they’ve been supplanted by the increasingly expensive hybrids. I don’t know if you’ve looked at a seed catalog lately: Holy crap, man. The price of hybrid seed is going through the roof.”
He says he’s happy to be a grower who mostly uses open-pollinated seeds, and to be a seed saver.
“Not that creative breeding doesn’t deserve reward, and not that people who breed things don’t deserve to have their efforts compensated for,” he says.” “But as a gardener with choice, I’m going to stick with the history stuff and saving seeds from it and spreading them around — and leave the hybrids to those who feel like they have to grow them either through disease issues or getting at the highest possible yield for a square foot.”
For gardeners who are looking for certain traits in their plants, which as disease resistance, now is a good time.
“What a time to garden!” Craig says. “There are varieties for every desire, every need. What a great time to take advantage of all of that diversity.”
Craig uses spreadsheets and family trees to help him track what he grows, its lineage, and what he must grow and what he wishes to grow for research.
“It’s a Rubik’s cube that is only getting more complicated with each passing year,’ he says.
One year Craig crossed indeterminate heirloom tomato varieties with other indeterminate heirloom tomatoes and grew out all eight hybrids and loves them. Since then he’s only grown out saved seeds from three or four of them, and now he wants to go back and grow out saved seeds from the others.
Last year Craig grew out Cherokee Purple crossed with Lillian’s Yellow, and produced a new variety he’s calling Lillian Rose. It’s potato leaved, pink on the outside and yellowish on the inside. It’s still only on the third generation, so there is more work to be done.
“I’ve shared seeds of that with lots of people around the country, even around the world,” Craig says. “There must be at least 30, 40, 50 people that are helping me in searching.”
He’s also experimenting with Dwarf Tomato Project varieties. And there are some of his favorites, like Cherokee Chocolate and Cherokee Green.
Craig researched seed pretreatment in a bonus module for the Growing Epic Tomatoes course. He found that the best way to remove the greatest number of potential diseases from a seed is to expose it to 122° water for 25 minutes.
“But if you’re growing a lot of plants, that’s hard to do,” he says. “So do you pick and choose? If I save seed off a plant that might have had fusarium or a heavy dose of early blight, should I go ahead and do that?”
“The literature is maddeningly absent of a lot of this type of information just because there’s so much you could research. So those of us that are playing this playground are, are kind of building some of this in ourselves. Getting the definite list of which disease can get into a seed coat: That was really, really hard because you can go to five different websites and see five different lists.”
Lists don’t agree on what pathogens can be removed by hot water or bleach, but Craig is doing the work to figure it out.
Vermicompost in Seed Starting Mix
Now that I have access to a consistent supply of vermicompost from my friend Jack Chamber’s company TerraThrive, I am adding it to all my seed starting mixes.
I now use 20% vermicompost in my seed starting mix, and I am absolutely convinced that the vermicompost’s contribution to soil microbiology is making a difference once the roots hit it.
I am also experimenting with soaking seeds in vermicompost extract. Seeds that I soaked overnight in 20% dilution of extract germinated faster and grew more vigorously.
Craig says tea, gibberellic acid (rooting hormone) and nitrate can all assist seeds, though precision remains a problem.
Tomato Disease Resistance
“A lot of people have asked me, what have you done in the Dwarf Project to breed disease resistance into the dwarfs?” Craig says.
He says the project is not even touching that yet.
“That is such hard work to do,” he says. “You need fields where you can plant hundreds of plants, and you need to have known disease in that field. You have to know you have septoria or early blight or fusarium or nematodes. You have to run controls. You have to have stock that you know has resistance or tolerance that you breed in. So this is why, to me, the seed breeders working on that sort of thing do deserve the big buck bucks. Because it’s really, really, really hard to do.”
The Dwarf Tomato Project wanted to focus on the fun stuff: What color are they? What do they taste like? What shape are they? How’s the beauty of it? The fascination of it, the diversity of it? What does it taste like?
“That after all initially is what gets gardeners interested in gardening,” he said.
Absence of Pest or Disease Problems
Craig says that he rarely gets a criticism in a review for his book “Growing Epic Tomatoes” the reviewers say he didn’t write enough about a certain pest of disease. He says they weren’t included in his book because he didn’t have to grapple with those specific issues in his garden. He’d much rather refer readers to experts on the topics.
“Gardening is such an incredibly broad topic that there is always going to be something that is not in your bailiwick and then you feel kind of guilty because you can’t cover it to the extent that you think people need it covered,” Craig says.
Having hosted “Growing a Greener World” for 12 years and going, I want people to learn about pest and disease management all around the country — because I know the viewers are from all around the country. But my home garden is in the Southeast and won’t experience the regional problems others confront.
With my upcoming Organic Vegetable Gardening course, I struggled with the fact that I could not demonstrate the top pests and top disease issues for each vegetable that I was demonstrating how to grow. I finally reconciled with the fact that I can’t cover everything because of the diversity.
Craig points out that during office hours in the Organic Gardening Academy, students become teachers in the group because they have knowledge that they can share with gardeners who confront the same issues there do where they live.
Craig’s Growing Mix Preferences
Craig’s growing mix of choice was long Metro-Mix 360, but he’s found two suitable replacements. He spoke with SunGro, the maker of Metro-Mix 360, and learned the company had become unhappy with its supply of vermiculite, maybe due to a supply-chain issue. It was not up to their standards, so they stopped putting vermiculite in the mix.
SunGro recommended Metro-Mix 830 instead, which is similar to Fafard #3B and contains perlite rather than vermiculite. Craig says he liked it, and seed starting and transplanting went OK, but the mix is a bit chunkier. The shredded wood is not as fine, so when he is starting seeds he sieves the mix first. He also found the mix absorbs more water.
Craig also tried Sunshine Mix #5, called propagation mix. It comes sieved like Metro-Mix 360, which he likes. He suspects he will need to use warm water to pre-wet it because it appears to be water-repellent.
Coir & Peat
I don’t like to use the word hate, but I’ve hated the coir I have tried so far. Anyone who has followed along as I have trialed coir has seen how stunted the seedlings get. They germinate, and then they remain half an inch tall for a long time.
It comes down to the salinity content of the coir and the lack of buffering. These are issues that should be resolved before the product reaches consumers. The producers want to get coir out for sale while spending the least amount possible on the product. The end result is a very unsatisfactory user experience. Who wants to go back and buy that stuff if they’re not having success with it?
“It should not come to the gardener to have to figure this out by trial and error in debt or stunted seedlings,” Craig says. “It should be the R&D behind these products that does this work so that you get a handy little cheat sheet saying this is what’s different about using this.”
I’m trying to dial down on how much peat I use, but frankly, I love working with peat. It works well and is a proven product, although I acknowledge its environmental downsides.
I’m still bullish on Plentiful PittMoss, which is a paper-based, non-peat, non-coir product. Once you get over the slight learning curve of how to use it and how to water it, it’s amazing. The results have actually been better than anything else I’ve ever had.
I also just started sowing directly into Soil³. They have a new veggie mix with better drainage, and when I have used it, the seeds in Soil³ are the first to germinate.
Soil³ is not available everywhere, so as much as I recommend it, I know it’s not accessible to everyone. Craig makes this point: “Gardeners garden where they garden, and we can’t know what their mix of material is where they’re gardening, but I have to always remind myself, this is what I use. I can’t assume that this is what everybody else around the country has at their disposal.”
I hope you enjoyed my conversation with Craig LeHoullier about seed starting and more. If you haven’t listened yet, you can do so now by scrolling to the top of the page and clicking the Play icon in the green bar under the page title.
What are you trying for the first time this seed starting season? Let us know in the comments below.
Links & Resources
Some product links in this guide are affiliate links. See full disclosure below.
joegardener Online Gardening Academy™: Popular courses on gardening fundamentals; managing pests, diseases & weeds; seed starting and more.
joegardener Online Gardening Academy Master Seed Starting: Everything you need to know to start your own plants from seed — indoors and out.
joegardener Online Gardening Academy Organic Vegetable Gardening: My new premium online course membership opens in 2023. Sign up for the waitlist here.
joegardener Online Gardening Academy Beginning Gardener Fundamentals: Essential principles to know to create a thriving garden.
joegardener Online Gardening Academy Growing Epic Tomatoes: Learn how to grow epic tomatoes with Joe Lamp’l and Craig LeHoullier.
joegardener Online Gardening Academy Master Pests, Diseases & Weeds: Learn the proactive steps to take to manage pests, diseases and weeds for a more successful garden with a lot less frustration. Just $47 for lifetime access!
joegardener Online Gardening Academy Perfect Soil Recipe Master Class: Learn how to create the perfect soil environment for thriving plants.
“Epic Tomatoes; How to Select and Grow the Best Varieties of All Time” by Craig LeHoullier
“Growing Vegetables in Straw Bales: Easy Planting, Less Weeding, Early Harvests” by Craig LeHoullier
Disclosure: Some product links in this guide are affiliate links, which means we get a commission if you purchase. However, none of the prices of these resources have been increased to compensate us, and compensation is not an influencing factor on their inclusion here. The selection of all items featured in this post and podcast were based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Rain Bird, Corona Tools, AeroGarden, Milorganite, Soil³, Greenhouse Megastore, PittMoss, Territorial Seed Company, Earth’s Ally, National Wildlife Federation, Proven Winners ColorChoice and TerraThrive. These companies are either Brand Partners of joegardener.com and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.