What a change weatherwise! When we wrote last week things felt like mid-July, while this week things feel like Mid-March. In the south metro we’re seeing flooded fields, while in the northern and western parts of the state, the rain has helped to make a dent in drought conditions. Cool temperatures are expected to continue through the weekend, and planting will be delayed on most farms.
Holding transplants
With nearly a week of cold, wet weather, many growers have had to hold transplants longer than expected. We expect to see night time temperatures start to rise again next Monday, but you might already have transplants that are getting leggy, nutrient stressed, and ready to go outside. A few methods for reducing stress include:- Avoid the urge to turn on the heat: By lowering the overall temperature of your greenhouse or high tunnel, plant growth will slow down. This may also help to harden off your plants and reduce transplant shock.
- Beyond reducing the overall temperature, a commonly used strategy in the floriculture industry is the DIF method, in which you keep your greenhouse warmer at night than during the day, which limits stem elongation. One adaptation to the DIF method that may be easier for growers trying it for the first time is the “cool morning pulse”. With this approach, you would reduce the greenhouse temperature for 2-3 hours at dawn, bringing the temperature 5-10 degrees (F) lower than the nighttime temperature (Cox, 2007).
- Another method for reducing plant growth is to use gentle physical agitation. Agitation should gently bend the plant stems; too much force can lead to breakage. When plants are agitated 1-2 each day using physical brushing, running a stick or pipe over the tops, adding fans, or even brushing your hands through your plants, they slow their growth and put energy towards reinforcing the stem and building up their waxy cuticle layer. Take care to only do this when plants are dry, and with clean hands or sterilized equipment to prevent disease spread.
Finally, keep eye out for plant diseases. Bacterial diseases, like bacterial canker in tomatoes and bacterial spot in pepper, can thrive in the greenhouse, so remove any plants that look unhealthy to avoid problems in the field.
Bacterial spot in peppers transplants. Photo: Purdue University.
Fine tuning spring fertility applications
When our team visited 100 vegetable farmers in 2023 to do soil testing and assess soil health, we learned that interpreting soil tests and choosing appropriate inputs is a significant challenge for most vegetable growers. Because of a lack of clear guidance, most growers are applying a set amount of inputs every year (for example, 1 cubic yard of composted manure per field), than doing tailored calculations. Based on the need for more specific guidance, we’ve created a calculator tool that allows you to choose a crop, indicate how large of an area you plan to grow (e.g. ⅛ acre of pumpkins), enter your soil test info, and then select inputs from a dropdown menu. The tool tells you the best balance of inputs to use for your crop needs, and how much to add to your planting area. It includes inputs commonly used in organic systems that are notoriously tricky to calculate like compost. You can access the calculator tool directly here.
The embedded video below walks you through how to use it.
Crop updates
Brassica growers with a history of cabbage maggot, keep those row covers handy! The cooler weather this week is going to stretch out the risk window for cabbage maggot
– the egg-laying adults don’t mind cool weather. If you have brassicas
scheduled to go out into a field where you recently terminated a cover
crop or terminated a lot of weeds, these fields will be most at risk –
cabbage maggot is really attracted to the smell of decaying plants.
Potato planting is touch and go as weather allows. Colorado potato beetles
sometimes show up before plants emerge, I’ve seen the adult beetles
wandering around fields just waiting for plants to emerge. A key time to
manage Colorado potato beetles is when the first generation of larvae
hatch from their eggs – they are most susceptible to insecticides, and
are the base the rest of the summer’s population will be built on. Scout
and be ready to act.
Sweet corn, beans, melons, and squash:
As a general rule, it’s worth holding off on planting your direct
seeded, heat loving crops until the soils warm up and dry out a bit. The
longer these seeds sit in cool wet soil, the more opportunity they have
to rot or be eaten.The northern part of the state
is in the window for seed corn maggot damage. Like cabbage maggot
above, the cold-weather loving fly lays its eggs on large-seeded crops,
and the maggot that hatches burrows into seeds, preventing germination
or producing stunted, distorted plants. Delay planting if you have a
history with this pest – once the soils warm and plants grow quickly,
damage is much less likely. Growers in the southern portion state are
out of the risk window for this pest.
Rhubarb: Rhubarb
harvest is here. Read the following tips for a successful rhubarb
harvest, and to ensure healthy plants in the years to come:
- Rhubarb should not be harvested in its first year so that the plant can successfully establish itself. Wait until the second season before harvesting. Wait until the third season to harvest if you started from seed.
- Start harvesting stalks when they have reached full length. Each variety is different but stalks range from 12 - 24 in. long.
- When harvesting, only remove half of the fully developed stalks from the plant.
- Do not use a knife to cut the stalks from the plant. Instead, Hold the stalks firmly with your hand, pull, and twist.
- If you see a seed stalk emerge, make sure to cut it off immediately. If you let it go to seed, the plant is using energy unnecessarily.
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