Considerations for Cutflowers in a SubTropical Climate
- alexis0993
- Oct 5
- 3 min read
What does it mean to grow in a subtropical climate?
It means everything is trying to actively die, so it's a lot harder to keep it alive.
Welcome to South Carolina.
There are two different types of subtropical environments - humid and dry. Want to take a gander which one we are in Charleston, SC, Zone 8b? Yup - humid. Humid. Humid. You swim through the air come July and August with the average humidity rates being 88% and 90% respectively per month.
What does this mean for flowers? Lots of disease. Fungal. Bacterial. You name it, we probably have it.
There are several strategies to combat diseases born from high humidity. As a flower farmer, I'm trying to grow as many stems in the tallest heights possible. This means I intensively plant my flowers to maximize my yield per square foot. I also know that when I do this, I'll need to make sure I have successions of flowers arriving because I WILL get disease. It's not an if here, it's a when. Especially since we strive for the lowest amounts of inputs possible, even if they are organic.
Spacing
As a home gardener, go with recommended spacing. Typically that's 6, 9, 12 or 18 inches apart (check the back of your seed spacing or plant tag). That allows air flow in the stems, helping to decrease disease rates. If you start to notice spots on the leaves of your flowers (looking at you zinnias), try stripping the leaves on the bottom third of your plant. I can't space my flowers out like the above, but I can strip the bottom third of the leaves if I'm trying to make a row of zinnias last before my next succession is up.
Mulching
Soil splash back is a major cause of contamination. I notice disease spreads much faster on the flowers I haven't gotten to mulching versus the ones that I have. I use a super fine pine mark mulch that breaks down quickly and amends the soil as it goes. This is one of the reasons other farmers plant into landscape fabric. A barrier between the carrier of the microbes (ie the soil) and the plant is a must.
Preventative Inputs
Much like humans, the healthier your plant's immune system, the more your plant can fight disease. When I first started gardening, I was given the advice that I should use an organic biofungicide as disease prevention every 2 weeks. The science behind this so much fun - the good bacteria of the spray act as a barrier, prevents spore germination for fungae, but also boosts the plant's immune system. I rotate my biofungicides every 2 weeks to help with resistance. The two I've found work well are Serenade and Regalia. If you can't find them in your local garden center or landscape supply, try Amazon, Seven Springs Farm, or Arbico Organics.
A Note on Proper Drainage
We have a very high water table being so close to the coast and in a region of the state referred to as the Lowcountry. I cannot emphasize how important it is to ensure the soil is draining adequately. When water saturates the soil over long periods of time, anaerobic bacteria begin to breed. The soil where this is happening has a sharp, lip-curling smell. Think low-tide over the marsh (IYKYK). Even though our soil is sandy-loam, with the water table so close to the surface, many plants can become water logged during rainy seasons. I have raised beds on part of my farm that are only 6-8 inches above ground level and have weathered an 1,000 year flood and standing water. A little height goes a long way.
Know When to Call It
These three steps and considerations can help prevent disease from setting in or give you a good, long go before calling it a day. By late July/August, no one's garden or farm looks good. Sometimes, for sanity's sake, it's better to call it and start again for our Second Spring in September.
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