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[Frog Pajamas]

Hi, I was hoping you could help me with what would make my seedlings the happiest. I believe I had the humidity too high on my acacias at first (especially the Acuminatas), and  realized I'm working on trial and error so far. They are all still healthy, especially the Maidenii, but I want them to thrive of course. I'm indoor gardening and have a heat mat and 10,000 lumen T5 light to work with. The seedlings range from just post -germination to about 6 weeks old.

I thank you and my new babies thank you!

[New Wisdom]

I've noticed that plants like tenuiflora (and other mimosoids) don't do very well under lights.  They thrive outside in full sun from the very first day they're germinated.  Hot temps and nice strong full sun with maybe a little bit of shade in the afternoon.

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[Frog Pajamas]

Well, I may wait to germ any more until early Spring, but do you think lights will get them through the winter? Or better to acclimate them outdoors even now?

[Mandrake]

Tenuiflora and most of the commonly discussed acacias thrive actually quite well under T5 fluorescents during the seedling stage. It's true that, in order to maximize growth, sunlight is the best as long as the temperature is not too cold (nor extremely dry and hot when they are young) but they can do fine under lights the first months. T5s can be kept at a few inches from the seedlings to make the best out of them.

About moving them outdoors, unless you leave in a very warm zone, I'd wait until spring. The lack of light can be just a growth limitation, but low winter temperatures will kill tenuiflora seedlings, or at least stunt their growth badly. I have germinated them indoors in late fall under T4 and T5 fluorescents, and moved them outside in march (southern Europe) with nice results. Actually the first challenge was getting them to survive the next winter outside.

As for the other conditions indoor, ideally warm-ish temperatures, I'd say 40%-70% relative humidity, and good drainage in the soil. Some air flow is good because it makes them exercise, thickening the stem and spreading stronger roots, so throw in a little fan if you can. Water not too frequently, don't let the soil dry out completely in the seedling stage but the older they get, the longer you can wait between waterings without stressing them out. And keep checking the leaves for nutrient deficiencies.

Keep us posted,

Mandrake

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[Frog Pajamas]

Perfect, thanks. I'll drop the light down a few inches, add a fan and keep on keeping on. Got my first teniuflora sprout today, so I'm excited to watch that one grow.

How should I go about checking for nutrient deficiencies? Soil test kits,  or are there signs on the plants themselves? 

[Mandrake]

If the substrate you're using is at least part organic (i.e. 30%+ compost or peat) there should be enough nutrients for the first couple months or more, unless the pots are very small. Professional gardeners check for EC (electro-conductivity) in the soil in order to monitor the amount of available nutrients and to decide whether fertilization is required, but I don't think that's necessary with mimosoids. Up-potting them regularly as required is part of the growth cycle and fresh soil will provide new nutrients, and adding 10-20% worm castings or alfalfa meal works nicely and allows for slow nutrient absorption on demand.

But regarding the leaves color, just keep an eye in the new growth. Whenever the new sets of leaves show clearly a lighter green once they have spread out completely (they can be paler in the early sprouting and that's ok) and the light has not changed, it might be time to add some dilute fertilizer to the water. Nitrogen, calcium and iron mostly. Or move them to a larger pot with fresh food.

Mandrake

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