The Connection Between Temperature and Bloom Size
As a flower farmer, you’re looking to grow perfect, massive, beautiful blooms.
You know - when you see those flowers that are so picture-perfect that they look unreal. That every single petal and stamen and curve is exactly as if it were perfectly sculpted.
They are the blooms that we drool over on Instagram and the ones that brides and grooms pin on Pinterest and the ones that capture the heart and souls of the general public.
Flowers are pretty amazing, and when you come across them in the field you want to hold your breath and ask yourself “Oh my god, did I grow this?”
Which is great when it does happen
But there are so many times when it doesn’t happen.
For most of us, those perfect blooms are somewhat less frequent. Your zinnias are deformed or throw a lot of singles. Your dahlias have a green center and their petals aren’t full and fluffy. Your ranunculus are on short stems with teeny-tiny blooms and so on.
I get it. We’ve been there many times. And it happens again and again.
We tried everything. Tried foliar sprays, tried saturating the soil with cold water, tried buying special mycorrhizae - nothing worked.
We still would get single flowers with blown centers and small petals.
Here’s the thing - everyone always assumes that flower quality is based on the skill of the grower, which is true to an extent. If you are a bad grower, you’re going to have bad product regardless of what you do.
On the other hand, we found that our single, smaller blooms weren’t our fault.
And chances are, they’re not your fault either!
Back when the Zinderella series of zinnias had first come out and they were all the rage, there was an outpouring of reports that people were getting a lot of single-form zinnia blooms instead of the fluffy scabiosa-form zinnias.
As more people started reporting back including the people that did have fluffy scabiosa-form zinnias, a trend started becoming apparent.
For example, farmers in states like Montana and Maine were getting a higher proportion of scabiosa-form zinnias, while farmers in states like Nebraska, South Carolina and Idaho were getting a higher proportion of singles. And there were a higher proportion of doubles as the season went on, with the highest proportion of scabiosa-form at the end of the season.
As it turns out, the region and environment have a lot to do with the quality of flower you grow, everything from stem length to size of the bloom to even the color and how full the petals of the flowers are.
Cool temperatures mean big flowers
The big takeaway of this post should be that cool temperatures = big flowers
What we learned is that the cooler the temperatures, the longer it takes to go from bud to fully bloomed flower.
This is why the blooms are best in the early spring as well as late fall when the temperatures are at their lowest but not quite yet freezing either.
The low temperatures do have a tradeoff in that the flowers are much slower as far as production goes, but although it may seemingly take forever for that bloom to start opening up, the bloom you do get will be wonderfully massive in size and be absolutely fabulous with big fluffy petals and a giant head.
For instance, some people ask regarding how Japan growers get such large ranunculus. Nearly the size of a softball, it’s assumed that it is just a special Japanese ranunculus they are growing.
I have a feeling that part of the size is not the fertilizer they use, or the breed of ranunculus or any special magic trick in particular aside from the temperature that they are grown in.
(The Japanese are notorious for perfecting the cultivation of everything from sweet peas to muskmelon, so I would believe that they have perfected growing practices for ranunculus as well).
Japanese ranunculus are kept and grown at the perfect temperate - cool, with bright light and great for dragging out the bud stage of the ranunculus so it can spend the maximum amount of time and energy beefing up the blossom.
I’ve noticed some growers who are doing greenhouse growing during the winter such as Urban Buds in St. Louis have the most perfectly fluffy and perfectly formed dahlias.
On the other hand, you may have observed that dahlias during the middle of summer oftentimes show their green center very easily and the petals are not necessarily the most fluffy and perfect - usually appearing more like a wet bird than anything Instagram-worthy!
However, those same dahlias at the end of the season - when the temperatures start dipping down into the 40’s at night - are picture-perfect, with perfectly formed arrays of delicate petals.
While you’re not going to find that the dahlias are as prolific in the summer, they are going to be much more well-formed. It’s kind of this weird trade-off with flowers - you get fewer flowers but better quality in the end.
So the question is, how can you take advantage of this phenomenon as a flower farmer?
Even if you don’t own a greenhouse that you can do winter growing in, here are a few ideas
Know your growing conditions
If you live somewhere where the summers are relatively cool and late - Northern Minnesota, Alaska, the coastal east and west states, islands, you will have a longer period of the cool and bright growing season which means that you’ll be able to extend the optimal period for perfect flowers much longer.
If you live in the Continental U.S. or even in the Rocky Mountain Region like us, you’re going to have a more difficult time because you are generally going to have a short spring and a short fall when those temperatures are optimal. You may get lucky one year and have an unusual extended period of cool weather - but don’t necessarily count on it.
Grow more spring and fall flowers
There are some flowers such as ranunculus, anemones and sweet peas that bloom in the spring and then there are some flowers such as dahlias, mums and scabiosa-flowered zinnias that bloom well in the fall. If you know that you’re going to be getting the best flower quality in the spring and the fall, you may want to time your crops to take advantage of those optimal bloom times.
On that same note, you may decide that you don’t want to plant big fluffy flowers for the summertime, and I wouldn’t blame you for doing so. Our dahlias in the middle of summer are all blown open and terribly crazy looking - we can still use them, but they don’t quite look the same. We instead focus on growing other items - basil, daucus, zinnias, celosia and other flowers that don’t require the same conditions to look their best.
Make sure you fall plant your spring flowers
The longer that you can grow your spring flowers in cool conditions, the better. Although there is usually a daylight requirement in order to trigger blooming for flowers like sweet peas and ranunculus and poppies, if you can get them established earlier in the fall they will have a longer period of bloom in the spring - which means more time to create those perfect blooms.
Start your summer flowers earlier
One of the tricks I’ve learned over the years is to get certain summer flowers started earlier to take advantage of the (relatively) cooler days of June before it really starts to get hot in July.
For example, if I can get zinnias started indoors, planted outside and kept protected from frost/freezes not only will they bloom longer but they will also give you a good flush of really perfect blooms for the first harvest - because of that extended cool period that allow those flowers to develop fully and slowly.
Use the first harvest as your first pinch
On the same note, instead of preemptively pinching your plants (which I know, is required for certain plants in order to have them be productive and produce multiple stems) you can just wait until the main stem blooms (which will be the highest quality bloom if grown at the right time) and harvest to the base of the plant. While the successive blooms won’t be quite as impressive, you can get at least one great high-quality bloom.
Be OK with lesser quality blooms
While it is nice to have big perfect fluffy blooms, it isn’t needed all the time. There are plenty of flowers that do well without needing that cool period to form big crazy blooms, and in some cases you don’t want them to get that big since they may interfere with other materials in the floral design. As I mentioned, there are plenty of materials that do well without those cool, bright conditions - basil, celosia, gomphrena, sunflowers and eucalyptus to name a few - and it’s also great to take a break from the big fluffy flowers to grow something else!
I hope this helps you to understand the connection between growing conditions and bloom size and quality a bit more! I also hope this helps you to be a bit more forgiving of yourself when your blooms don’t turn out perfectly.
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