How to Time Your Fall Brassicas - Ep. 307

[00:00:00] It is officially the beginning of summer. The tomatoes are loaded with fruit. My squash is doing its aggressive best to take over their half of the gardens. The pole beans are flowering, the cucumbers are trellising, the potatoes and onions are coming out of their beds. It's hot. It's weedy. And right now, while all of that is happening, I am also starting cauliflower seeds under the lights in my basement and trays and trays of other brassicas are getting started in the greenhouse. And I know how that sounds.

[00:00:28] But if I wait for another two weeks to start those seeds, I won't have cauliflower this fall. The calendar doesn't care how busy I am or how much the summer heat has me convinced that fall is a long way off. The time to start is now.

[00:00:43] Fall gardening doesn't start in September. For the crops that take a long time to produce, so your broccoli, your cauliflower, cabbage, maybe brussel sprouts, it actually starts now in late June and early July. If you've never had a productive fall brassica bed, it's almost certainly because you started too late and it took me a lot of years to master this.

[00:01:08] Welcome back to Just Grow Something. I'm Karin Velez, market farmer, horticulturist and somebody who has learned most of what I know about fall brassicas from missing the planting window a few too many times in my earlier years. This episode is about fall garden planning and specifically about the crops that require you to be thinking ahead right now in late June and into July when literally nothing about summer conditions suggests that fall is coming.

[00:01:35] This episode actually connects directly back to episode 296 where we talked about succession planting and keeping garden beds productive from the first thaw to the last frost. If you haven't listened to that one, go back and start there. I will link to it in the show notes because what we're covering today is the fall half of that conversation.

[00:01:56] Specifically, how to time the crops that take 70 to 100 days or more to mature so that they're ready to harvest before your first frost. We're talking about the timing, why it matters, how to calculate it for your specific first frost date, and exactly what to do if you're sitting here thinking you may have already missed the window. Because you might not have, but we need to move quickly. Let's dig in.

[00:02:24] So before we jump into fall gardening, I want to read an email question I got because I think the answer is something that many of you can use right now. This email came from Carol and it says, Hi Karen, I'm growing my zucchini inside of a tool hoop this year because of pest pressure. I bought parthenocarpic seeds from Hudson and they have grown extremely well, but no flowers. Is this because of the seeds that I used?

[00:02:51] Love your podcast. And yes, this has been a horrible year weather-wise. Thanks for any insight you might have, Carol. And so I subsequently emailed Carol back and asked her for some specifics, including which varieties she planted. When were they started? Were they started indoors or were they direct sown out in the garden? And if indoors, when were they transplanted outdoors? Because all of those things matter to my answer. Carol responded that she had checked her garden notebook. Love this. Love this.

[00:03:22] And she told me the variety name and when she had direct sown the seeds. Because she had this information, I was able to tell her that, yes, it was a little too early for those to be blooming and that she'd likely see those starting in like the second week of July. And if everything looked healthy, then to just keep doing what she was doing. How did I know this? Because the variety she planted is typically a 50 to 55 day zucchini.

[00:03:48] And she direct sowed the seeds in the garden on June 1st. So the plants are less than 30 days old. And so they're still putting on their vegetative growth and they're not ready for flowering. All this from the fact that Carol wrote down which varieties she was growing and when she planted them and I could find the days to maturity. This is basically just one more vote for the garden journal.

[00:04:14] So that when you're questioning the timing of something happening in your garden, you have the information to go back and look. So you're not guessing at when something is supposed to be flowering or fruiting or ready to harvest. So good job, Carol. And good luck with that zucchini. Okay, so we're talking fall gardening in general.

[00:04:37] But I will be referencing brassicas a lot just because they are the main fall crop that tends to take the longest to come to maturity. But all of the things that we're talking about including your timing can also apply or should also apply to everything else that you want to grow. So if it's leafy greens like lettuces or something that don't take as long, the timing still matters. But we're talking about brassicas a little bit more specifically because they do take so long, right?

[00:05:05] And this is the reason why the timing for these brassicas actually catch so many home gardeners off guard. The crops that I'm talking about don't mature in 30 or 45 days. They take 65 to 100 days or more from transplant to harvest depending on the crop and the variety. So I have used the MU Extensions Vegetable Planting Calendar for years and years and years.

[00:05:34] And it specifically says for Missouri specifically, and it's broken into like east and west and central areas, it has the dates broken down for every single crop that you might want to plant both in the spring and the fall. Now, this hasn't been updated in recent years as far as I can tell. And so it doesn't necessarily take into account what I've seen in my own gardens in terms of our heat and our later average frost date in the fall.

[00:06:03] But it is still the data that I work from personally here in west central Missouri, which is now zone 6B. So what it says for broccoli is that you should be planting those starts. So transplanting right around July 25th through maybe August 5th for a fall crop. So the days to maturity from transplant would be about 70 to 80 days. For Brussels sprouts, they're saying to get them in the ground by July 20th, maybe as late as July 30th.

[00:06:33] You're looking at 90 days or more for maturity days. For cabbage, they recommend planting between July 20th and August 5th. So days to maturity on those would be between 70 and 80 days. And then for cauliflower, again, around July 20th through August 5th, days to maturity on those would be 65 to 75 days. Now, notice that for central Missouri, broccoli, cauliflower, cabbage, and Brussels sprouts

[00:06:59] all have fall planting windows that open in mid to late July. And the thing about those dates is that they are for setting out transplants, not for when you start the seeds. And so we know our seeds take between four and six weeks of indoor growth before we transplant them outside. So that means if the transplant out date is late July to early August,

[00:07:24] then seed starting needs to happen in late June or early July, like now, right? Brussels sprouts are probably the most extreme example. They need the longest time in the garden of any of the common like brassicas. So typically 90 days or 100 days or more from transplant to harvest. And so that MU calendar shows them with a July 20th to July 30th transplant window for my area. That is not a lot of runway.

[00:07:54] So if you're listening to this in late June, if you're in a climate like mine, you have a very narrow window before you lose the chance entirely for this year, right? The University of Minnesota is also very specific about this. You know, for Brussels sprouts, they say to sow the seeds in June. So this could either be indoors or directly in the garden for a fall crop. And they also note that direct seeded plants can need up to three more weeks to mature than transplants,

[00:08:23] which matters a lot when you are racing a frost date. The same math applies everywhere, though the specific dates obviously are going to shift based on your first frost. So if you're in a shorter season area, say like zone five, and your average first frost comes around mid-October, then you need your transplants in the ground by late July to early August to have any chance of a full head before frost.

[00:08:49] If you're in a zone seven garden, right, with like a first frost in early November, then you have a little more time. But not as much as most people assume, because some of these crops need that cool fall weather to actually form a quality head. And the fading number of daylight hours also makes a difference. Now, if you're lucky enough to have an extension service in your state that has a planting calendar like the one from MU,

[00:09:18] by all means, use it as a really handy starting point. And it keeps you from having to always go back and do the math. But as always, keeping a garden journal so that you have your own notes for what performs well and what doesn't in your own garden is a really fantastic idea so you can adjust from year to year.

[00:09:48] So I think the thing that most gardeners don't understand or that they don't fully internalize is that these brassicas that we're talking about don't just tolerate the fall weather. Fall is actually when they are at their best in most areas, I think, especially if you have a very short runway in the spring. All four of those crops that we just talked about are cool season brassicas. They grow okay in warm weather, right?

[00:10:17] The leafy vegetative growth phase doesn't need cool temperatures. But when it comes to the time to form the head or the curd or in the case of Brussels sprouts, the individual little sprouts, you know, along the stalk, cool temperatures are what drive the quality of those heads or those curds. Summer heat can actually harm the quality of the developing head. Heat while the leafy plant is growing is fine.

[00:10:47] But once those heads start to form, you want the cool air. So this is what I really misunderstood the first few times that I tried to do fall brassicas. I really, really thought that I needed to wait until the weather started to cool before I could transplant. And all I was doing was getting great leafy growth and that I just would not get any type of a head or a curd or anything on these.

[00:11:12] And so I know that planting in the heat of the summer almost seems counterintuitive. But this is what, you know, we as gardeners here in Missouri have noticed for a very, very long time is that fall broccoli just has a better quality than the spring broccoli here, right? Fall grown broccoli heads are tighter. The flavor is better. And that's because they're not racing to beat the summer heat.

[00:11:37] So you also have a longer harvest window, which is honestly why I switched to growing broccolini in the spring instead of regular broccoli because it doesn't form a head. I just save the heading broccoli for the fall. The cauliflower situation is even more specific. Cauliflower is maybe the most temperature sensitive crop in this group, even though it sometimes doesn't seem like it. But high temperatures can prevent proper head formation entirely in cauliflower.

[00:12:06] This is what we call a blind bud where the plant just never produces a curd. I have had this happen over and over before. Research on head formation has basically shown us that daytime temperatures above 86 Fahrenheit and nighttime temperatures above 77 Fahrenheit can keep the plant from forming henny head at all.

[00:12:29] And at lower but still warm temperatures, you just get loose leafy curds instead of that, you know, tight, compact head that we're looking for. Cauliflower grown when it's heading into summer heat can really be a disappointment if you don't get the timing right. But growing into the cooler temperatures of fall, that same plant is going to produce dense, firm, very flavorful heads.

[00:12:56] The chemistry of the plant responds to the conditions in ways that translate directly into what we eat. Brussels sprouts take this even further, right? The flavor of Brussels sprouts really improves with the cooler fall weather. And the sprouts can stay in the garden as long as temperatures stay above 20 degrees Fahrenheit, which means a frost doesn't kill Brussels sprouts. It actually improves them.

[00:13:21] The cell walls of the sprouts are more intact when the cold slows their metabolism. And then the sugars concentrate in a way that makes them just so much sweeter than anything that you would get in the spring. Most people, I think, who have decided that they don't like Brussels sprouts have probably only ever eaten spring grown ones or supermarket ones. A properly grown fall Brussels sprouts, if you harvest it after the first frost, is a completely different eating experience.

[00:13:51] Cabbage is a little bit more forgiving of temperature extremes than the others, but it also stores better and develops a sweeter, milder flavor when it matures in the fall rather than rushing it through the summertime. So I usually grow a batch in each season. And cold, tolerant cabbage varieties can handle below freezing temperatures late in the season, which also is going to extend your harvest window.

[00:14:22] Now let's talk about how to actually figure out your timing, because the specific dates that I gave for Central Missouri obviously don't apply directly to you if you are in a different region from me. The calculation is straightforward, though. So, you know, once you do it once, you'll basically have it for every year. I have a little piece of graph paper that I made, and I'm going to guess it was probably 12 years ago,

[00:14:48] that basically just keeps this math right in front of me and gives me the approximate planting dates for the varieties that I commonly grow based on their days to maturity. And I just reference that every year. But you're welcome to do the math every season if you want to. So for transplants, you take the days to maturity of the crop, and we're going to add 10 to 14 days as a buffer.

[00:15:13] This is your short day buffer, and this is going to account for the slower growth that happens as the days shorten and the temperatures drop. Okay? And then we're going to count backward from your average first frost date. If you're someplace that doesn't get a frost, then this would be your Persephone date, your Persephone period. So the date when your daylight hours drop below 10 hours a day. Okay? That gives you the latest date to transplant outside.

[00:15:42] Then you count back another four to six weeks from that to find when you should start those seeds indoors. So let me walk through this with broccoli as an example for a garden with an October 10th average first frost. Okay? So if we assume that this is a mid-range variety, you know, that matures in about 70 days, then we're going to add 10 days, that short day factor. Okay?

[00:16:09] So that means we need 80 days for that plant to mature before the first frost. So if our first frost is October 10th, we're going to count back 80 days. That means our transplant date would be July 22nd. Okay? Well, we need four to six weeks to get that plant started indoors and allow it to grow on a little bit.

[00:16:31] So if we count back four to six weeks from July 22nd, we are looking at needing to start our seeds indoors somewhere between June 17th and June 30th-ish. Okay? And that is why we're talking about this now. If your first frost falls in October and you are listening to me in late June, early July, you may have just barely enough time.

[00:16:56] If your first frost is in mid-September, some of these windows have already closed for the season, but we'll get to that in a second. For Brussels sprouts, the math gets, you know, a lot tighter. If you have like a September 25th first frost date and you need 100 plus days from transplant, then you actually need to be starting seeds in May or very early June.

[00:17:18] That's why Brussels sprouts often get kind of left off of the fall garden plan entirely because, you know, gardeners run the numbers and they realize they missed the window before they even thought about it. For gardeners in longer season zones, the season or the windows shift forward and you have a little bit more flexibility.

[00:17:35] So if you're like in a coastal area of the Pacific Northwest or you live in the Upper South, even parts of the Southwest, you can grow fall brassicas with transplanting windows extending into late August and sometimes even September. But even there, Brussels sprouts need to go in earlier than most people expect. So we want to remember to use our average first frost date, not the earliest recorded frost.

[00:18:03] You want the calendar to work for, you know, an average year, not the worst year on record. And then choose variety days to maturity very carefully. A variety that is listed at 90 days, obviously, takes longer than one at 65 days, right? And so that difference is going to matter when you're working backward from a fixed frost date.

[00:18:23] So the usual recommendation is to choose, for example, you know, fall broccoli varieties with like a longer growth cycle of between 60 and like 85 days. And this is specifically because we want the heads to form in those cooler temperatures. So that longer runway gives us more of a chance to do that. You know, the opposite is true for our spring plantings. We want to choose those fast maturing varieties so we beat the heat. But for fall plantings, the calculation is the opposite.

[00:18:54] But if you are finding yourself short on time, then maybe look for one that's a little bit more fast maturing if you're close to missing the planting window right now. For your direct seeded stuff, generally you want to add a couple of weeks. Because the soil temperatures are warmer at this time of the year, you absolutely can direct sow all of your brassicas. It just means that you need to monitor that bed very heavily for weed pressure.

[00:19:21] And you also have to watch for critters that may want to eat the sprouts and then thin them out as they pop up, okay? Plus for something like direct seeded cabbage, it can take up to three weeks longer for them to mature than if we're doing them from transplants. So if you're direct seeding any of these rather than using transplants, then make sure you're kind of adjusting your days to maturity accordingly. And then remember that row covers can buy you a little bit of time on the back end.

[00:19:50] So a good frost cloth or a row cover can actually extend your harvest window by a few degrees and a few days to even a couple of weeks, which can totally make the difference between a partial harvest and a full one if you have a season that runs maybe just a little bit late. Okay, so depending on when you're listening to this, you are in one of a few situations.

[00:20:17] If it's late June, then you are right on time in most zones for broccoli, cabbage, and cauliflower. You still have a window for Brussels sprouts if your first frost is in late October or later. So get seeds started immediately. Every day that you wait is going to narrow the window on the back end. And starting seeds just a little bit earlier, say like late June rather than mid-July,

[00:20:44] actually gives your transplants just a little extra size and root development before they go out, which generally works in your favor with these crops at this time of year. You just want to avoid letting the transplants get too big, and we certainly don't want them root-bound before they go in the ground. Now, if it's mid-July when you are hearing this, you're still in the range for broccoli, cabbage, and cauliflower in most like zone five and warmer gardens.

[00:21:13] Brussels sprouts are probably getting really tight, but if your first frost is like mid to late October, you may still have some room, especially since those can continue to be harvested after the first frost. Run the math for your specific frost date and the variety that you're choosing before you give up on them. If it's late July or early August, for most mid-range season gardens, the window for Brussels sprouts has pretty much closed for the season. Broccoli and cabbage are still very much worth doing,

[00:21:42] especially if you can find transplants, or if you have some, you know, some started seeds, or if you have some varieties that have like the right maturity window. In shorter season gardens, the math may not work out for some of these. So again, you know, look at your first frost, your days to maturity, figure out when your day length decreases below those 10 hours per day, because that's when the plant growth all but slows to a halt. So if your season is too short for any of this, right? Like if you're gardening in zone four,

[00:22:11] where you guys have first frosts in September, fall brassica production is kind of challenging. Brussels sprouts probably are not worth attempting for a late fall harvest. I just don't think you have enough days. Broccoli and fast maturing cabbage and cauliflower varieties probably have the best chance with you. You might focus on kale, which is still a brassica, but it matures more quickly and it's even more cold tolerant.

[00:22:39] And then maybe direct seeded greens like spinach and arugula that are going to carry your fall garden through without needing the lead time that, you know, the heading brassicas do. And then one more thing about heat and the timing that sometimes surprises gardeners. You don't have to wait for the cool weather to transplant these out. I made that mistake over and over and over again. In fact, you shouldn't wait, okay? The vegetative growth phase,

[00:23:09] the weeks when the plant is building the leaves and the root structure before it's ready to form that head, it can do just fine in the summer heat. What you're trying to do is time it so that when the plant is finally ready to form that head or that curd, that the temperatures have dropped into the range where that happens really well, okay? That's why starting seeds in late June or July makes sense. Even when it's 95 degrees outside,

[00:23:35] the plant will spend the hottest weeks just growing vegetatively. By the time it's heading up, fall should be arriving right on schedule. I love a fall garden. It's cooler to work in. There are fewer pests and diseases. The weather is a bit easier to predict. It truly is just a joy. So if you've never planted for the fall harvest or it's been a while,

[00:24:02] I absolutely encourage you to try this season. Now, if you need a little help with this, I've got you covered. I run a free five-day email sequence called the Fall Garden Challenge. I take you through figuring out where to fit these plants in because if you didn't plant this out in the spring, you might be looking at your garden going, uh, Karen, I don't have any place to put these plants. So we plan that out, okay? I also walk you through crop selection and the layout and the planting calendar

[00:24:31] so you know when you need to be getting these seeds started or when you need to purchase your transplants. You can go to justgrowsomethingpodcast.com slash fall to get signed up. Like I said, it's free and you'll get one email per day from me walking you through this process. Justgrowsomethingpodcast.com slash fall and of course, I will leave that link in the show notes. The fall garden shouldn't be a second thought

[00:25:01] or an afterthought. It really is the second half of the same growing season you started in spring and it requires the same kind of forward planning that your spring garden planting did just with a different anchor on the calendar, okay? You plant in spring relative to your last frost date. You plant in fall relative to your first frost date or your daylight hours. The math is the same. The timing is just a little harder to see

[00:25:30] because the summer heat makes October feel like it is a really long way off. Trust me, it is not. Now, go register for the fall challenge and then go track down some seeds. Until next time, my gardening friends, keep on cultivating that dream garden and we'll talk again soon.