Succession planting is kind of like running a relay race. Only a few crops occupy their place in the garden for a full season. Most either grow fast and are gone by midseason, or, though they are slow to mature, and take a long time to fill their allotted space. Some are not even planted until midsummer, for a fall harvest. In all these cases, well-thought out succession planting schemes can make sure that every square foot of the garden is as productive as possible, throughout the longest possible season. There is also another trick, known as “inter-planting,” where crops that are natural companions are planted together in the same space at the same time, also sometimes called “companion planting.” The smaller the garden is, the more benefit you’ll get from taking the time to figure out creative ways to use the time and space that each season allows you.
Single Crop Successions
One of the primary goals of succession planting is to stretch the harvest period. It is traditional to plant both sweet corn and peas in succession, so that their overall harvest periods are stretched out. This is usually done in one of two ways. Either a range of varieties with different maturity periods are planted all at the same time—which I call varietal succession—or the same variety is planted periodically, say, every week or two over the course of the spring—in temporal succession—so that the plantings will mature one after the other. Another example of this second kind of succession planting is staggered planting of lettuce and other salad greens, to maintain a fairly regular harvest throughout the season.
In general, and for beginning gardeners in particular, varietal succession is a bit easier to manage than temporal succession. This is because all of the varieties planted will get the same treatment and grow under the same conditions, allowing only their genetic diversity to provide the variation in harvest date. No management is required. With temporal succession, though, the situation is a bit more complicated. As spring progresses, the days get longer and the weather warmer; usually it gets somewhat drier as well. Each of these factors affects the germination, growth, and maturation rates of the crop, and also when it will reach harvestable size.
For example, two rows of the same variety of peas planted two weeks apart in March will usually mature only one week apart in June, because the germination conditions at the time of the second sowing will likely be much better; the young plants will grow faster in the longer days, slowly catching up with the first crop. But even this difference is relative, as the slightest differences in weather between the two plantings can throw the schedule off in either direction. After years of experience in a particular garden one gets a feel for the season, but for beginners the garden calendar can stretch or shrink like a weather balloon.
With fall crops, this same process of time stretching and compressing happens in reverse. Even a couple of days difference in midsummer planting dates at higher latitudes, where the days begin to shorten rapidly in late August, can lead to a harvest date difference of two, or even three, weeks! To make this kind of relay planting work requires the experience to recognize subtle cues in the garden that foretell the kind of season it’s going to be—even before the weatherman knows. We’ve all heard these kinds of tips: that corn can be safely planted when the oak leaves are the size of a squirrel’s ear; or that a thick band of color on a woolly caterpillar foretells an early fall and cold winter. The years of observation that went into the creation of this kind of folk wisdom—called phenology by those scientists who study the timing of bird migrations, blooming of shrubs, and insect life cycles—was done by gardeners like yourself. Your own observation, in your own garden, will eventually provide you with the best and most reliable guides to the scheduling of successions.
Even the smallest garden can use varietal succession to stretch the harvest. For example, when planting direct-sown crops like beets and carrots, mix the seed of several different varieties before planting. Grow them just as you normally would, but this way you’ll have both the early crop and the late crop in the same row. With a slow germinator like carrots you can go even further by mixing in a little radish seed, thus interplanting it with the carrots. It will germinate immediately, and the radishes will be ready for harvest by the time the carrots need thinning; in fact harvesting the radishes will even help with the job!
Succession-planting two or more different crops in the same space can be more or less complicated than single-crop successions, depending on how you look at it. For instance, it’s fairly simple to plan a tomato crop that follows spring spinach. Spinach should be planted outdoors very early in the spring (while the tomatoes are just getting started in the greenhouse), yet spinach can’t take the heat; conversely, tomatoes need warm weather to succeed and can’t be set out in the garden until it arrives, by which time spinach must be harvested or it will have run to seed. Thus the two crops can ideally share the same space in the garden without a scheduling conflict (though their other needs should be considered, as we discussed on the crop rotation pages).
There are many other, less obvious combinations that can be worked out, and playing around with all the options can be fun, and can provide some good eating in the process. The key is to organize the information you have about the various crops and your particular garden, then “map” all these details onto the time allotted to you by the season, to see which crops might fit together well in a succession plan.
Here’s one way to organize this data: take the list of crops you grow and arrange it into early, middle, and late-maturing crops; I call them one- two- and three-monthers. Next, make a second list arranged by whether each crop favors hot or cool weather (these should have a note telling if they are better adapted to spring or fall). To do this, make a simple flow chart showing the beds and/or rows down the left-hand side, and the weeks of the season across the top. Then take the longest-maturing crops that are most essential to you and block out the time and space they’ll need according to your plan. Next, look for natural combinations with other long-season crops that want the opposite set of conditions. A spreadsheet like Excel is ideal for this, or if you want to get more extreme, many online sites offer software that will do a prettier job.
Here is an example from USDA Zone 3b-4a:
- Plant peas the second week of April and harvest from the second week of July to the first of August.
- Take out the peas and transplant leek seedlings that were started back around the first of May.
- As the leeks grow use the soil from the edge of the pea beds to hill the leeks for blanching.
- Or if you planted the leeks in holes, set out lettuce or endives, or direct-seed some kohlrabi on the bed edges.
Any of these will work; it’s just a matter of which fits into the overall rotation scheme you’ve worked out to match up with your succession scheme.
Once you’ve figured out all the possible fits between long-season crops and midseason crops, place the leftovers in an appropriate spot on your flow chart, then fill in with the short-season crops. It is possible that you’ll have some spots that will be available for multiple plantings of really fast-growing crops like garden cress, arugula, or spinach.
Another possibility to keep in mind is that, if their growth habits are compatible, some crops can overlap. This is particularly true if you are using transplants (which I recommend, especially for small gardens). For example, we set out Brussels sprouts transplants in mid-May, directly into the bed of spinach that was sown a month earlier in mid-April. As we harvest the spinach, the Brussels sprouts plants are allowed more and more room; by the time they need the whole bed, our spinach is out of the ground and into the freezer. We could just as easily inter-plant lettuce seedlings with the Brussels Sprouts. Whenever you have a situation where a large plant takes a long time to size up, you have an opportunity for mixed succession or some other form of interplanting.