Seedling and transplants

Asked March 27, 2020, 3:29 PM EDT

Hello I started some seeds indoors for the first time. I have attached photos of broccoli and lettuce seedlings. They were started about 4-7 days ago ( I mistakenly did not record start date). My questions: --Do they look okay to you? -- Should they already have true set of leaves? The broccoli seedlings seem a little long to my novice eye... -- I understand that when 1st set of true leaves appear, then is time to transplant to larger pot? Or directly outdoors? --Can I just transplant as they are in their current soil and then thin to proper spacing ? Or is best to gently cut into the soil seedlings are in, then try to transplant individually? Gardening is keeping sane while isolating. I really appreciate your advice ! Thanks so much, stay well. Adriana

Montgomery County Maryland

5 Responses

Hello Adriana,

The links below are our series on indoor seed-starting and may be of some use:
https://extension.umd.edu/hgic/topics/starting-seeds-indoors
https://extension.umd.edu/hgic/topics/seedling-care
https://extension.umd.edu/hgic/hardening-vegetable-seedlings

This link is a chart of planting dates for central MD:
https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/grow_it_eat_it/Publications/GE007%20Vegetable%20Planting%20calendar%20for%20Central%20Maryland%202018.pdf

Your seedlings may benefit from more direct light, as it looks as if at least one of the lights isn't directly overhead unless it was moved for the photo. Plants can stretch in response to insufficient light, and will also tend to lean towards a light source. Once the true leaves appear, as these are cool-season crops, you can plant them outside, as per the calendar linked above. Tender seedlings would need shelter from frosts until they have adjusted; the third link of the the above trio discusses hardening-off seedlings.

You can try to gingerly tease the seedlings apart if you'd like, or just plant them as one and thin (cut) whichever of the two appears weaker. The second of the three links above contains a video on seed starting; around the 10-minute mark the person discusses thinning seedlings before transplanting. (If you continue watching, take his lighting distance advice with a grain of salt, as some modern light sources are brighter than the tubes he is probably using in his fixture.)

Miri

Thanks so much !
I will add/update my setup as recommended.
Could you please discuss a little about LED vs various fluorescent light options. Im very confused as to which is best. I currently have LEDs, which I understand dont produce heat. But Im not sure if " no heat" is an advantage or not...?

Thanks again. Im so grateful for your help and this service.
Kind regards

You're welcome.

There is a lot of debate online among indoor plant growers of all types regarding LED versus fluorescent (and others impractical here) lighting options. Expensive light meters can help determine which have the best light output (in the proper range of wavelengths) from any source for plant growth, but for hobby growers are unnecessary. In general, LEDs tend to be more energy-efficient and put out less heat than fluorescents. Fluorescents put out less heat and are more efficient than conventional incandescent-type lights, though few of these are manufactured as plant grow lights because of this. The trade-off is that LEDs tend to be pricier, being a newer technology, though may have a longer functional life than fluorescents, which can need replacing over time as their light output drops off.

Warmth from fluorescent fixtures can be a benefit in cool rooms, or a detriment when conditions are too warm. For seed starting, the added warmth is not likely a problem. It could be a benefit for germination if light fixtures are used on multiple shelves on a rack, where the fixture below a seed tray on the shelf above can provide gentle heat that can speed germination. Those conditions would also promote more rapid drying of the soil, however. Other indoor growers, such as with orchids and vivariums, are more concerned with heat buildup since they have more specific ranges of ideal temperatures and often are using the lights in more enclosed setups. Essentially, any light fixtures that indicate they are designed for growing plants are probably best, as they should have light wavelengths concentrated around plant use. (This doesn't mean you have to go to the extreme of using the unpleasant neon-purple plant lights, though.) Your LED unit is a common design and should be fine to use, though perhaps oriented closer to the leaves. (We don't have a set distance recommendation; you may have to experiment and watch out for leaf bleaching and desiccation from too much light.)

As touched-on above, the other important factor is the physics law of how light changes intensity over distance. In a nutshell, the further away from a light source, the less light a given area (like a leaf) gets by greater and greater factors. Small changes in distance can have significantly different impacts on the plants. When used on seedlings, the lights are typically kept quite close to the leaves and separated by more distance as the seedlings grow to avoid burning. The plants can be lowered or the light fixture can be raised; whichever is easiest.

Miri

Miri, you are the best, thanks so much for your detailed feedback. I will now make a cup of tea, forget about COVID for a while and dive into your answer.
Thanks !!!