Succession Planting Part I: The Best Crops for the Job
We shared our personal sowing chart in a late January post. And, admittedly, it's a very aggressive growth chart by general gardening standards. We grow aggressively to maximize our terribly short growing season, and to inspire others to stretch their own predisposed gardening beliefs. My goal here is to break down our approach into bite-sized, actionable pieces for those hoping to try their hand at the deliciously-rewarding art of successional planting, wherever you may reside.
In order to achieve successional harvests, you need to be aware of what foods can be grown successionally. Certain summer crops you plant just once like tomatoes and peppers, others have a wide variety that matures at different times like cabbage and brussels sprouts, and others still grow over a wide range of temperatures and can be planted throughout the growing season such as beets and carrots and broccoli. I will lean on some popular crops and use them to demonstrate how we approach succession planting.
Two other important factors for planning extended harvests include your last (spring) frost date and how much space you have for food production. If you don't know your zone or last frost date, you can find it here. Also fun to peruse if you're a map geek like me is the USDA hardiness zone map; truth be told this is more of a dynamic map than it appears as climate change is impacting these zones and their data does not include the past 5 years or so. In Minnesota, our last frost is early May, and we make haste during our brief, four and a half month frost-free growing period.
At the Seed to Fork homestead, we transplant our first succession four to six weeks earlier under "row cover" - a simple and economical PVC hoop house covered with 5ml painters poly fastened to the PVC with large binder clips. On a really good year, we have our first starts out in the garden by the last week in March. By doing so, we are eating food from our garden by the last frost date. Additionally, we are able to get a third - or sometimes fourth - succession of broccoli, cabbage, and kohlrabi. And that, my friends, is why we do it.
Plan to start your first succession at least four weeks before your last frost date -- up to 6 weeks if you are willing to experiment with early, uncovered crops. Some years your last frost will be several weeks earlier than average. We plan for that every year, and hope for the best. You just never know until you try -- and I highly encourage you to stretch your season and your comfort zone and give it a try with at least a few seedlings this spring.
Top Picks for Successional Plantings
Before I dive in, here is my short list of things you need only sow once a year in a cold climate like ours: tomatoes, peppers, eggplants, corn (dent and sweet), summer squash, winter squash, potatoes, sweet potatoes, watermelon / musk melon, rutabaga, brussels sprouts, cucumbers, shelling beans, leeks, onions, herbs, and edamame. I discussed our strategies for growing these crops in my Ultimate Garden Plan post earlier this winter.
Below are my top picks for successional planting based on over 20 years of garden experimenting and learning, including our own strategies for extended harvests.
What does this mean, you ask? Brassicas are a genus of cruciferous vegetables in the mustard family including broccoli, cauliflower, cabbage, kale, kohlrabi, and brussels sprouts. In our family, this genus of plants is a huge part of our daily, year-round diet. Some of them tolerate heat rather well like newer broccoli varieties, while others do best very early or very late in the growing season such as cauliflower. While kohlrabi can grow throughout the hotter summer months, I have come to love the crunch of a fall kohlrabi over all other times of the year, though I'll confess the first one in late May holds a special place in my heart - and belly. This genera of vegetables is the bread and butter of our successional garden planning as several varieties spread out over the entire season yield really consistent harvests.
Buy seeds not starts! Be diligent in your research. This is the most important advice I can give you: starting from seed means you can proactively select for maturity and your climate. I scour the catalogs, studying the days to maturity, selecting varieties of cabbage suitable to cold climates that mature early, mid and late season. Hands down, this is the easiest way to achieve an extended harvest — grow several varieties that mature over a longer span of time. We grow at least 6 different cabbage varieties and transplant them into the garden in early Spring; they mature over the course of 6 weeks or more.
Additionally, we sow them indoors and transplant to the garden at least 3 times during the growing season. We sow them both one AND two months before last frost, then again 10 weeks before after our first fall frost. Our earliest sowing gets transplanted into a covered hoop house as described above about four weeks after they germinate. The result is heads of cabbage, bouquets of broccoli, and crunchy, sweet kohlrabi from sometime in June through late October or early November.
Oh the garden carrot never disappoints, does it? I find the best and tastiest carrots are those sown in the height of summer (late June/early July) and harvested in early October. The later, the sweeter as fall frosts increase sugar storage in the roots, but carrots can be harvested from July-October with just a little bit of planning and execution.
We direct sow carrot seeds as early as the soil can be worked, which is mid-April in Minnesota. We then sow several rounds of carrots wherever we can find room for them throughout late spring and early summer. We will never tire of the garden carrot nor have too many on our hands. We sowed 3 or 4 rounds of carrots last spring/summer and will plant 4 or 5 this year. A steady stream of carrots is most satisfying.
Carrots can germinate with soil temps as low as the mid-40s, which is pretty cold! Carrot seeds benefit from being mixed in with compost for more evenly sowing — and so they have a good water-holding medium while germinating; the seeds are really small and almost every gardener will begrudgingly disclose their tales of the thinning (death) of dozens of carrot seedlings in the name of spacing. Continue to sow carrots every few weeks until the middle of July, or do one sowing early and then your fall carrot sowing by the Fourth of July in the northern climates. Sowing in the height of summer requires much more attention to the moisture than in the cooler spring weather. You have been forewarned.
We err on the side of less is more, and try not to sow them closer than 1" apart. Saves seed, saves money. Another option is to purchase pelletized carrot seeds, though some garden experts will caution that germination rates on pelletized are not as high as straight up seeds. We use both, for what it's worth. They take what feels like forever to germinate, so don’t despair. It can take up to 3 weeks to see your carrots sprouting. Keep them evenly watered during this important time in their lives.
Sow carrot seeds every few weeks between mid-April until mid-July, as space allows. If you are tight on space, you can interplant them with your tomatoes (think of it as a border plant and frame in the bed with a row of carrots around the outside) or other crops that will grow more vertical than horizontal. We give them their own space, but space is not at a premium for us anymore.
Lettuce & Leafy Greens
This is something I should be really good at, but over the years I have consistently overlooked my indoor seed-starting window for these, and then I run right into late Spring, and my young, direct-sowed lettuce falls prey to early heat waves, goes bitter and bolts.
Here's what you (and I) should do. Sow lettuce indoors as this will give you a big jumpstart. Start seeds 4 weeks before your last frost date (mid-April in Minnesota). Thin them to one head lettuce seedling per pot or a few leaf varieties per cell after true leaves form. Eat what you thin out — they’re micro greens! By early May, you will have strong plants ready to be transplanted. If this is your favorite thing to grow, start it early and start a little bit every week in April to really get a good head start.
Lettuce is a low light plant and will do well even under a sunny windowsill, so no fancy light setup is required (though they will love the extra light if you have it). It's not a fussy crop, but it does do best in cooler weather. This is my stumbling block — I am so fixated on the hotter weather crops and my annual flowers that I overlook this. I have learned that lettuce is more cold-hardy that I imagined, so even direct sowing some lettuce in your garden in mid-April will yield you some salad bowls by Memorial Day.
Another fantastic crop that can be sown multiple times over the course of early spring through summer resulting in a steady stream of roast yumminess and sautéd greens. I love, love, love to grow, cook, and consume beets and their greens. The more I grow, the more I love them.
We actually sow our beets indoors and transplant them out. Sow beets as often as every few weeks starting in early spring. I did an experiment last year where I direct sowed beets in the garden at the same time I sowed them indoors in pots and under a heat pad. The ones that I started indoors and transplanted matured faster and I thought did better overall — more uniform in growth. We now employ this method for beets, though I know this isn’t the standard for large-scale farmers.
On a small scale, I find it the superior way to grow them. I use a 72-plug flat and a self-watering mat; for the summer sowings I do them right outside our kitchen door on our deck, so I can keep an eye on the moisture levels; they sprout quickly. I wait for true leaves and then transplant them into the garden. With this method, we eat fresh beets from mid-June all the way into October. We sowed beets three times last year, and I plan to sow them more often this year.
Pole and Bush Beans
They are summer crops, to be sure, but if space allows these can be an excellent successional crop when sown even just two times in the summer. We did this last summer, and will again this year. Bush beans produce a lot all at once while pole beans produce over a longer period. Planting both at different times ensures an extra-long string bean harvest. I highly recommend this approach.
We direct sowed our pole beans in early June, and then sowed our bush beans a few weeks later in mid-June. Check your varieties for days to maturity and sow them so that the bush beans produce several weeks after the pole beans start producing -- or vice versa. You should get a week or two out of a bush bean planting while poles will produce all summer long until first frost. Either way makes for a great extended harvest in your summer garden. We enjoyed a continuous stream of string beans from mid-July until first frost.
Now that you've read this far down, I'm gonna let you in on a little secret. If you grow tomatoes in your garden, you likely already succession plant. Why? Because tomatoes are one vegetable that has received an abundance of attention from breeders over the decades and centuries. It has become more and more diverse with each passing year. And when you plant a few different varieties, you extend your tomato harvest handily. Succession planting can be as simple as that.
The Bottom Line
Grow your own starts and select a few different varieties for each vegetable to extend your harvest simply by growing both early and late maturing varietals.
Indoor sow your earliest broccoli, cabbage, kohlrabi, cauliflower, kale, and lettuce starts 6 weeks before your last frost date indoors. Transplant out up to 2 weeks before your last frost date, depending on your longterm forecast.
Indoor sow another round of these same plants for fall harvest around beginning of July (this would work well for zones 3 - 6).
Beets and carrots can be sowed in early spring and sowed as often as your space allows through the middle of July. Sow at least a few times between mid-April and mid-July and you will reap harvests anywhere from late July - late October. Diligently water them while they are germinating. Can be sown indoors or direct sown.
Green beans can be extended by growing both bush and pole types, sown a week or two apart. Sow them when soil temps are warm in late Spring, and again two weeks later for extended harvests.
Choose several different types of tomatoes (cherry, paste, slicer) to extend your tomato harvest from early in summer well into warm fall days.
Does this give you some sense of how we approach it? I live and breathe this so sometimes I doubt whether this is approachable enough or not. I will dive deeper into the art of it all - including the mental stamina required - in my next blog post.