The Dandelion Planting Schedule
Imagine having a special device plugged into the ground that tells you when to plant everything. Guess what: You do!
1Where I live, most gardeners start sowing seeds around May 24th, and don’t plant out their transplants until the “first new moon in June”. These are old rules of thumb, and they are reliable - but there are many things that can be planted before those dates, and there is a much better way to know when things need to be planted.
When taking a quick stroll around the yard in late April, I see new grass; dandelion greens; coltsfoot flowers in the ditch by the road; buds on trees; and a handful of perennials poking up in the garden. To me, nature is saying that it is time for some things to grow, and thankfully, there is an area of study that is all about that sort of thing.
Phenology: It’s all About the Sun
Everything that grows in a garden does so relative to seasonal changes, and seasonal changes are a function of the earth’s orbit around the sun, which influences the length of day, and the amount of heat energy provided by the sun during each day. The soil absorbs the heat energy, and its temperature registers the seasonal change. Plants and seeds respond to these changes according to their individual characteristics. What this means for determining planting times in your garden, is that you can use perennials to gauge soil temperature changes because they respond directly to them. This approach to understanding seasonal change is called phenology.
Phenology is the study of periodic events in biological life cycles and how these are influenced by seasonal and interannual variations in climate, as well as habitat factors (such as elevation). - Merriam-Webster. 2020.
The idea behind phenology, as applied to planting times, is that since perennials are literally plugged into your soil – they are the best indicators of soil temperature in your garden (i.e. how much of the sun’s energy has been absorbed by the soil at a given point in the season) because their growth patterns are directly influenced by length of day and soil temperature at your location. Moreover, since different perennials have different needs in terms of soil temperature – observing different plants as they begin to grow in spring tells you how far along the season has progressed in your micro-climate. It is also the case that observing a particular plant as it moves through a set of changes during the growing season tells you how far along the season has progressed in your micro-climate.
There are many resources on the internet that explain how to use phenology to determine planting times, but what I find irritating about them is that there seems to be a different indicator plant for each vegetable - such as planting eggplant and peppers and irises bloom; or not planting beans into apple trees bloom; or carrots, beets and chard when daffodils bloom; or cabbage when quince blooms - and on and on and on. The problem these indicator plants that they are not much use if they aren’t growing in your backyard or right next door. As an alternative, I have a simpler approach to planting times based on what I consider to be the most ubiquitous perennial in North America – the humble dandelion.
The Dandelion Knows All
Dandelions have long taproots that go deep into the soil. They begin to grow very early in spring, and move through flowering and going to seed very quickly – so for me, they have three main stages of growth that all occur at the beginning of the gardening season: (1) emerging greens; (2) yellow flowers; and (3) white fluffy flowers. I suppose one could be even more sophisticated and break it down even further with short greens and long greens; flower buds and open flowers; and white flowers and blowing fluff. Never-the-less, I think it’s easier to keep it simple with green, yellow and white.
When I see the dandelion begin to grow, the soil is usually thawed just enough for the tougher vegetables to grow. When their flowers are yellow – the soil must be warm enough for a few more things to go in the ground, and when the flowers turn white, the soil is warmer still. Most seeds have what is called a “minimum germination temperature”, and this can range from as low as 2° Celsius to as high as 16° Celsius; and I think the dandelion is a good rough indicator of the range of these temperatures, with the greens indicating when the soil is approximately 5° Celsius, the yellow flowers indicating 10° Celsius and the white seeding-flowers indicating 15° Celsius. Based on that, I have developed the following table, where the stage of dandelion (green/yellow/white) roughly corresponds with minimum germination temperatures.
Planting Times According to the Dandelion
It’s important to note that none of these are perfect measures and that the dandelion is an approximate indicator. When you see it in its various stages – it is a reminder to start thinking about planting the things that can handle the soil temperature at each stage. If you are concerned that it’s a bit too early – wait a week after seeing the indicator – or wait until you see the indicator everywhere on your property as opposed to just the sunniest and warmest spots. It’s also the case that while a given plant might have a minimum germination temperature of 10° Celsius – like the tomato for instance – it’s optimal germination temperature is closer to 24° Celsius, and any germination at all will be obliterated by frost anyway, so there is no point in sowing them until all risk of frost is gone, unless of course you are planting under a cold frame or some other micro-climate. It’s important to know which plants can take a little frost as seedlings, and which can take a hard freeze. For all the things on the table I think the timing is right. All the plants on the table have optimal germination temperatures that are higher than the minimums. For me – since the season will gradually get warmer, using the minimum temperatures as a guideline works because even if you sow when it’s barely warm enough, the soil temperature will continue to rise and the seeds will be ready to germinate when it does.
Final Thoughts
This table doesn’t cover everything, and I’ve not not mentioned transplants at all. Suffice it to say; for the most tender of transplants (peppers, tomatoes, squash, eggplant, etc.) wait for the white fluffy flowers. For plants not listed, just find the plant on the table that is related – for instance, the cabbage time can be a proxy for the kale & broccoli time as well. By watching the dandelions, and relying on their schedule – which is determined by a multitude of seasonal factors – you get a more robust indication of when to plant a range of crops. They’ve been around forever and always seem to do everything at the right time. So this year - rather than feeling dread at the sight of these common lawn weeds - why not feel grateful for such a simple and useful means to organize your planting times.
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This is an edited version of a preciously released article. If you want more information, please read that article.