When to Plant (& Succession Plant): Using Margaret Roach’s Planting Calculator
In Vermont we frequently use the term “cabin fever” at this time of year, since it seems like such a long time since it was warm enough to spend our days outdoors. It’s easy to feel stuck inside and disconnected from nature, particularly for farmers and gardeners who start to feel accustomed to life in daily contact with the summer soil. So it is with a wave of euphoria that I shake off the mentality of winter to write these words: it is almost time to plant again. In some parts of the country, planting has already begun in earnest, but here in Vermont we still have a short time left to order soil and flats, and organize our seeds and planting plans for the season ahead.
When to Plant
As the number of days left for anticipation gives way to the days slotted for gardening activities, it’s time to get out our calendars and start counting backward from that all-important last frost date. At least, that is the traditional method – take your last frost date, subtract the number of days to maturity, and voila! Many math equations later, your planting dates start to take shape.
Since I am not particularly fond of math, however, I was very excited to come across this amazing tool for calculating planting dates: Margaret Roach’s Planting Calculator! All you have to do is plug in the last frost date in your area, and it gives you the planting date for every plant on your list. (For those of you who don’t know Margaret, it’s time to learn – she is a garden writer and radio show host, and her blog, A Way To Garden, is filled with great articles on how to grow just about everything.)
Succession planting is probably the single most important tactic for producing a consistent supply of vegetables all season long. Basically it means that rather than sowing everything at once, you sow a little bit at a time. (If you’ve gardened before, you have probably experienced the zucchini explosion that occurs when you plant them all at once. No matter how much you love zucchini, you, and your neighbors, only want to eat them so many days in a row.)
So how to ensure a reliable harvest that lasts longer than a few weeks? You can actually figure it out using Margaret’s planting calculator.
- For your first planting, plug in your last frost date.
- For your second planting, plug in a last frost date that is 1-2 weeks later than the first.
- For your third planting, plug in a last frost date that is 3 weeks to a month after the first date.
You will end up with three different planting dates for each crop that is planted, resulting in a harvest period that is easily a month longer than usual, and much more manageable. Another benefit of succession planting is that you don’t have to put all your eggs in one basket – if the first planting fails, chances are you’ll still get something good from the third one.
For crops that are direct-sown, like peas, carrots, radishes, and beans, you can follow this rule of thumb as well. However, I prefer to sow these on a weekly or bi-weekly basis throughout the summer. As space opens up in the garden when a crop finishes, simply seed that area to plants of a different family. For example, if you’ve just cleared out your first carrot planting, and the weather is warm enough, sow that area to beans. This practice, called crop rotation, will prevent pests and diseases that are particular to carrots from building up in the soil and will also prevent the soil from becoming depleted in key nutrients. It is always a good idea to topdress the soil with a little finished compost each time you sow a crop where another has just been removed. This way, you know the new planting have the nourishment it needs to thrive. This is particularly important for radishes, which will grow long stringy roots without readily-available minerals and nutrients.
The Limiting Factors
Keep in mind that succession planting also has its limits. You can only do so many plantings of peas, because once the weather warms up it may be simply too hot for this cold-loving spring crop to produce well. Likewise, some crops like eggplants, corn, or tomatoes may take too long to mature to be planted a month “late”, since fall weather might come before they can set flowers and fruit. For longer season varieties, a few weeks between the first and last plantings may be all that is possible, depending on your location.
That being said, I think it is always interesting to experiment and learn what the limits of your crops actually are. You may find that a late planting of tomatoes, covered with a layer of row cover on cool late summer nights, produces abundantly and shows no signs of blight. Late season crops usually have much less of the pest and disease pressure that is so prevalent in the spring, and fall harvests of broccoli are often more abundant, tender, and cabbage worm-free than their spring counterparts. It is also important to keep in mind that certain varieties are bred for different seasonal “slots” – some varieties perform well in spring, others in fall or winter. This is also related to how long a variety will store without spoiling – generally fall varieties store the longest. Make sure to choose cabbage, broccoli, carrot and beet varieties that are adapted to the seasons!
The best way to learn what planting dates work best for you and your climate is to keep records.
- Keep a notebook and jot down the dates each succession was sown, transplanted, and harvested, and make notes about how healthy the plants in that succession look at different stages.
- Mark the plants in your flats with the succession number written in pencil (not permanent marker – it will be gone within a week!) on a popsicle stick. For example, if it was the second planting, write a large 2 on the stick. Then transfer the stick to the ground when you transplant.
At the beginning of the season, with just your seeds and soil before you, it seems simple enough to remember these details. But no doubt some of you have experienced a certain bewilderment in the heat of summer, with multiple plantings of many different crops in different locations, and fervently wished that you had taken the time to take notes and make good plant markers in those hushed days of early spring.
So let this be your New Year resolution – calculate, succession plant, and keep track! You will learn a lot from these three tools, and your garden will be more manageable not just this year, but for the seasons to come.
Here are some links to our other great articles on starting seeds:
- An Indoor Seed Starting Workshop For the Home Gardener
- Vegetable Planting Guide
- Garden Planning - A Step By Step Approach
- Seed Starting Video by High Mowing Organic Seeds