Dear Brigitte,

Thanks for sending in your question. I’m guessing all the plants are in the same bed? It’s not easy to answer without seeing a photo of what’s going on. Possibly, the plants are still alive, just not growing as you expect them to. Are the leaves green on all the plants? Are some leaves yellowing and/or falling off? 

Please help us answer your question better by sending us some photos and perhaps some more details of the problems you’ve noticed. Thanks,

Lesley (DC master gardener)

Hello Brigitte,

Thanks for sending in the photos which really helps us try to figure out what’s going on with your plants. I’ve checked in with some of the other master gardeners as well. We think your plants look healthy. We suspect that the main reason that they don’t seem to be growing as you would expect them to is the excessive heat we’ve been having here in DC. We’ve all noticed similar lack of progress with our own plants. Heat typically affects new plants more than established plants, as they haven’t yet adapted to the environment and climate so your seedlings could be even more susceptible to our current heat wave. 

The lettuce could well be bolting (sending up long shoots for flowers and ultimately seeds) due to the heat - it is a cool weather crop. Bolting happens with longer day length and high soil temperatures.

You could try to cool the soil by adding a layer of mulch around all your plants. If there’s anyway of providing some shade, that could help. And keep watering as plants need more water in the heat and it will also help cool the roots. And take heart because your plants aren’t dying or diseased!

Good luck. Lesley

Hello again Brigitte,

Here's a reference from Oregon State U's extension service, which has lots of information about how heat affects plants and what to do about it. 

And another from U California 

These references are provided to help you understand and cope with what's going on with your little plants, and so you don't worry so much about them.

Lesley

You’re very welcome. I’m glad you’re not worried. I think it’s particularly bad this year, though, as it’s been so hot so much earlier.

Happy gardening

Lesley

Hi Brigitte,

Adding excess nitrogen as an add’l possible cause for plant stunting/malformation. As you noted, many soil tests do not attempt to measure nitrogen, instead they may or may not recommend that there is a possible lack of nitrogen since it wasn’t measured. On the other hand, already adequate N is equally possible.

Further,  many garden plants do not require high levels of nitrogen, such as beans (take N in from the air), tomatoes, peppers, i.e. most of plants we grow for fruit or roots. Large greens, ex. kale & collards, need only moderate levels of nitrogen, faster growing lettuce could maybe uptake more. Grasses, such ass turf or corn, benefit from higher levels of N, but even those can be weakened by excessive nitrogen. 
As soils warm, the increased temps trigger organisms in the soil to make more of the N available to plants. At optimum N levels this can beneficially match the increased growth rates in warm weather, the downside being that excessive N can impede the plants’ ability to take up copper and other essential nutrients, thus impeding growth, impeding water uptake, weakening stems, and weakening defenses against pests and disease.

Since standard soil tests don’t cover N, this leaves us to diagnosing from symptoms, which could have multiple causes. Hence multiple diagnoses.

Even corn, a heavy N feeder, can be impeded by excessive N:

Adding to the earlier suggestions of mulch, shade for cool weather crops such as lettuce (old sheet or burlap will do) and adding a recommendation to hold off on the blood meal, which is extremely high in N. 

The cupped leaves & reported lack of growth in the pepper plant could indicate too much N. A thick mulch of arborist wood chips in the pepper’s bed could help mitigate. Possibly following with a buckwheat cover crop to uptake & stabilize nutrients in the soil, preventing run-off. Cut down in place, slowly releasing for uptake by your fall crop.

As to heat effects, observing some of the garden plots in a local community garden, while peas are long spent, collards have slowed in growth, but hanging on where given some shade, unshaded lettuces are tending to bolt. However, many of the tomatoes, squash, melons, peppers, eggplants and beans are growing strong,, where heavily mulched, well watered and with only home compost amended soil for the most part. 

Summing it up: mulch, shade, hold off on nitrogen, cover crops, keep up your good watering & tending. Please keep us posted on your gardening! Your feedback helps us all!

Kate

Hi Brigitte,

Thanks for the update!

Yes, mulch in contact with plant stems could possibly produce damp conditions that favor pathogens, more research on this in trees/shrubs than annuals, but leaving an air gap around the plant stalk is likely preventative.

Using a mulch layer of arborist wood chips in the garden over time can build tilth https://s3.wp.wsu.edu/uploads/sites/403/2015/03/wood-chips.pdf, adding compost, fall leaves, etc., (top dress) & cover crops can contribute, without the cost or possible side effects of boosters. Sorry & puzzled that the instructions on the blood meal bag are to re-apply monthly since, with the exception of grass, trees, shrubs, perennials and many garden crops don’t need a big N boost.

As to agronomy, I don’t know of a text to recommend,  but Dr. Steinhilber, a retired UMD soil scientist, recently presented to DC Master Gardeners, the recording is available on the  UDC Master Gardeners website. https://sites.google.com/view/dcmastergardener/monthly-meeting?authuser=0, slide down to May meeting to access the recording & Dr. Steinhilber’s  slides & charts. After attending her presentation to MGs, I googled some of her other presentations to pros, which went into to much more depth on soils. Garden Professors publishes on soils and other garden concerns, https://gardenprofessors.com/my-soil-is-crap/ and And USDA has a soil survey website:  https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm

Glad to hear about your garden, and please keep us posted!

Kate

Thanks from our whole team!

Kate

Hello again Brigitte,

Since you have so much knowledge and experience already, plus great interest in all things growing, would you be interested in becoming a master gardener? UDC holds 2 sessions per year. See site for more information. I think you'd enjoy it and it would be great to have you join us!

Lesley

Hi Brigitte,

UDC MGs in the Grow DC/4H program grow seedlings for DC schools citywide, & offers some garden coaching (optional).

Seedlings are free, can be picked up at your choice of several locations. All schools need to do is sign up. (We just need to know how many schools to sow for and which centers to stock for distribution days). Grow DC/4H collaborates with Washington Youth Garden, OSSE, Food Prints, City Blossoms, etc.

To find out more, sign up for free seedlings etc. go to: https://docs.google.com/forms/d/1i6Qo4rHl9ifQlihxAVGRv-zyAgXAuPSZJaPa34eD9PA/viewform?edit_requested=true

Happy gardening!
Kate