Dahlia Crop Protection: Surround WP
If you follow lots of flower farmers on Instagram, you’ve probably seen it— the chalky white liquid being sprayed all over their plants.
So what is this stuff? It’s call Surround WP. It’s a crop protection spray. It’s made of Kaolin clay which is milled very finely into a powder that’s water soluble. It’s also OMRI listed (this means it’s certified organic).
I use a battery operated backpack sprayer to apply it. Hand held works well too. I have a My 4 sons sprayer- mine has held up well since 2019 and it’s still working great. I love that it holds a charge for forever! Battery operated is worth it if you are spraying more than 2-3 rows.
The mix rate is about 2-3 cups of powder to 1 gallon of water. I mix it to the heavier 3 cup side for my first application of the season. After you have a bit of a base on the plant, you can mix a bit lighter when you reapply. It will stay on through some rain but will eventually need to be re-applied. I do mine around every 2 weeks but that can vary depending on how much rain we have- sometimes it’s more often, sometimes not.
A light first application- I’ve learned to begin at a heavier rate and then spray lighter in subsequent applications.
It looks like you are spraying milk and at first, you will wonder if it’s doing anything. But it has to dry on the plant- that’s when it begins to show some coverage. Nice thing about the Surround is that you can spray it pretty much any time of day as long as it’s not windy. It’s not going to burn like a fertilizer or horticultural oil. You can also mix other things into the spray- such as fish emulsion. I would recommend spraying early morning or evening if you are going to mix other liquids/oils.
I spray it during the first 2 months of a dahlia’s growth cycle. After that, bud development begins and that’s when you want to stop. It never completely washes off - even with a lot of rain. I can always see a little bit of it on the lower leaves up until frost. But you don’t want it on your blooming stems so I stop when I see bud formation.
A heavier application
You can also see the other reason to reapply— the new growth will need covering. It’s easy to measure how fast your dahlias are growing in between sprays.
So what is this spray doing for my dahlias? Several things:
Sun protection - As my friend Daniel at Petal Pickers Flower Farm says— it’s like sunscreen for plants! That’s a pretty accurate description. It’s the plant version of the white sunscreen you see on people’s noses! It reflects light away from the plants and generally keeps them cooler (up to 10-15 degrees cooler). When I grew dahlias in landscape fabric, I would spray the fabric as well as the plants for maximum reflective qualities. I spray for sun protection when I see temps in the high 80’s and higher. I grow in straw mulch now but still use landscape fabric in my pathways so I spray the pathways when it gets really hot.
Powdery mildew protection- PM spores get on your plant leaves and start turning into white powdery disease evilness. Surround prevents the spores from getting to your leaves. It’s a great form of early season PM prevention.
Pest Prevention- It’s not going to keep everything from eating your plants, but it will lower the pest load. It can help deter small animals (deer too) from eating your plants. It has a nasty taste to them. It’s not a fool proof solution but it’ll help. For a more complete list of pests deterred, click here.
One last quick tip— Before your first spray, inspect your field very carefully for any signs of virus. It can be harder to detect under the spray. Also inspect before each spray- check the new growth because that’s where it’s going to be easiest to see virus developing once you have the spray applied. The spray is useful at helping to keep virus loads in your fields down because it’s helping to control pests that spread viruses. Also you can still check for virus even after spraying if you do it very early in the morning. I get a heavy dew most mornings and when the plants are wet, the spray is not chalky so I can easily inspect for virus during this time.
Surround WP has become an important part of our growing plan for dahlias. We always get hot at some point, we have loads of pests and powdery mildew always raises it’s ugly head— So to be able to handle all that with one solution— well what’s not to like!