Its easy to get confused when we see gorgeous photos on social media of other gardeners planting in other zones, and it is natural to think, “should I be planting my (insert your favorite vegetable here) already? Am I too late?” When should you plant and how do you know if it’s too early?
It seems like common sense that if you plant earlier, you are getting your plants off to a great start and getting a jump on the growing season, right? Unfortunately, planting too early for some crops may actually cause more harm than good.
What type of plants are we talking about?
This applies to warm season crops such as tomatoes and peppers. Also affected would be cucumbers, eggplant, gourds, and especially luffa. These plants originated in very warm regions and are much more affected by the cold than cooler crops.
You can always plant lettuce, spinach, broccoli, cauliflower, brussels sprouts, kale, peas and beans, onions, carrots, radishes, and other root crops early in the cooler weather.
Why is it bad to plant too early?
Springtime is often inconsistent, and so even if you get a nice warm Saturday and you want to plant all those peppers and tomatoes, the problem is that often the temperatures can fluctuate throughout March and April. Even when you have great daytime temperatures, you have to watch the nighttime temperatures. This is the real indicator of when it is too early to plant.
Here in Northern California, March days can be in the 60s and 70s, which seems ideal for planting. We can even get days pushing the 80s. But nights often dip down below 50. On occasion it can drop below 40. This is what harms your early planted crop. Even if the temperature drops for just an hour or two in the very early morning, that could prevent your plants from growing.
What happens is that plant goes into shock. You don’t even need to have a frost to have this happen. The plant is already trying to recover from the shock of the transplant, so when you add the huge temperature fluctuations on top of that, the plant can go into a sort of dormancy. You won’t see the plant growing new leaves, but more importantly, the roots won’t be developing. And transplant time is the time when we need those roots to develop the most to get it off to a great start.
Many times plants like tomatoes can recover once the overnight temperatures warm up, but it takes them more time to come out of that dormancy than if you had just waited a few extra weeks for the nighttime temperatures to improve. Peppers on the other hand, don’t always recover. They can sit in your garden growing incredibly slowly – or not at all – and never really produce a decent harvest.
Why is there so much confusing information on when to plant?
All you want to know is when to plant and how to know if it’s too early to plant. The problem with internet searches on the subject is that so many places repeat the same old adage – go by the average last frost date. That can be misleading, for a few reasons. First of all, every year can be a little different, and you take a gamble by going with a hard and fast date when the weather could frost up unexpectedly late in the year. And there can be slight regional or localized differences depending upon whether you are in a low spot or at elevation. Even something such as a predominance of morning sun or shade can really affect how long the cold lingers on the plant in the morning.
Throw away the “last frost date” concept. I’ve only found it useful as a guidepost, but not as a hard and fast. Now there is such better technology than there was when the old almanacs were printed on the Guttenberg press. Try an app-enabled wifi thermometer in your garden and use that in conjunction with the weather app on your phone. You can track all of the nighttime lows and plan the best date for planting specific to your exact garden spot.
Here in Northern California zone 9, many gardeners like to say that you should not plant before Mother’s Day. That’s generally a good rule of thumb. But every year is different, and some years could be colder later, so you always have to watch the weather and see what is happening.
