My Midsummer Dahlia Plan
It’s the end of our Spring bloom season even though it feels like it just started. It’s time to prune our dahlias back for Autumn. If you are new to dahlia growing, you may not be familiar with the idea and for years, neither was I!
First thing we need to do is determine if pruning is right for you. If you live in a climate where you have to dig your dahlias due to freezing soil temperatures in winter- this is not for you. Pruning dahlias mid season is for those who can overwinter tubers in the ground or who live in a climate where you are able to plant in February or maybe even can grow year round. The purpose of a midsummer prune is to give the plants a chance to rejuvenate new growth for better fall blooms and also to eliminate the load of leafy plant material during the extreme heat of mid summer.
If you live in a hot climate but didn’t plant until late April/early May, then there’s no need to do a mid summer prune. If your dahlias haven’t bloomed yet, leave them be.
The timing of the pruning can vary according to where you live. I’m a zone 7b South Carolina. I want my dahlias to begin reblooming around mid to late August. Re-bloom takes from 5-8 weeks usually depending on variety (and climate conditions). So now is a pretty ideal time for me. If you are hotter, you might want to wait a little bit to shift your bloom window a little later when your weather cools.
Here’s My Plan:
1. Remove the netting and any remaining organza bags. We will lift the netting off the beds, roll it up and place it at the end of the row. If we still have any bagged buds, off they come!
2. Inspection: We will visually inspect each row for potential virus. Those plants will be removed and burned. We will also inspect for insect damage that we need to address
3. Cut back. We will use electric hedge trimmers to take the bulk of the material off the plant and then clean up with clippers. We will be cutting back around 2500 plants so hand cutting each plant is not a feasible option. But hand trimming is just fine for your dahlia cutting garden. We will be sanitizing clippers between each variety. Since it’s not practical to do so between each plant, step #2 becomes very important. If you have a number of plants where sanitization can be done between each one, I’d recommend it. This is also a good time to get rid of any weeds that have crept in.
How much to cut back? Well this depends on how old your plant is. For our plants that we overwintered, we cut back pretty low, around 8”. For varieties that we planted early this spring, we will cut back by about half. I’ve found that you need a good strong tuber base under the plant to cut back really hard.
4. Spray. So we will spray most of our plants with Surround. This is a kaolin clay spray that will help prevent bug damage to the plants but most importantly will lower the temperature around the plants and prevent sunburn.
Some of our plants are side planted with crops that are going to flower this Autumn so we can’t use the Surround. We will spray those with organic insecticides according to what pests we noticed during our scouting in step #2.
5. Feed. We will feed the plants with a complete fertilizer (nitrogen, phosphorus, and potassium). We will go a bit higher on the nitrogen (to push green growth) this round and then future rounds will be higher phosphorus and potassium to push blooms. We will use a granular since the plants are cut back and we will have a lot of soil exposed. We will also put a light foliage fertilizer in our spray mix. The reason for this is that you’ll need rain for the granular to work in and activate. But ideally, it’s a good idea to cut back when you aren’t going to have rain for a few days b/c you are going to end up with a lot of hollow stems during this prune. So giving a foliar spray helps the plants generate new leafy growth to help cover those hollow stems. We will also mix in a fungicide on the plants that don’t get the Surround because we are going into a dry heat wave the next few weeks. Hot and dry is prime conditions for powdery mildew.
6. Re-install your netting. Go ahead and put that netting back up and set it in place. If you do it now, you won’t forget later and end up with floppy dahlias. (or if you forgot to use it earlier in the season, this is your chance to correct the mistake)
7. Water well. This is a time where you really want a drip irrigation system. If you are overhead watering, be careful not to rot your dahlias out. The plants are going to be a little stressed when you have messed with them so much but in the long run will appreciate the love you’ve given them.
It’s important to pay attention to your plants after pruning, the next 2 weeks are crucial. Watch your weather patterns- give them extra water if you are really hot. If you end up in a rainy situation, watch out for rot and fungus. If you give them your attention for this short period, you’ll reap great rewards in the fall.