Overwinter plants indoors under artificial lights

Hi,

Here in Iceland, zone 6, there are several plants I must overwinter indoors.

However the largest challenge is lack of sunlight. (It also affects me, but that is another topic for talk!)

At this time of the year, my south oriented windows only receive about 1 hour sunshine per day, because of the low sun over the horizon and some nearby mountains, and i live in a valley. Days are rapidly becoming quite short. Between November and February no sunlight will ever reach my house and daylight will only be 3 hours in polar winter days (often cloudy and overcast).

Polar winter days only have light between 11am and 3pm, with the sun rising about noon and setting around 2pm. But it is very low, just crawling above horizon.

Artificial light is a must and plants seem to suffer already. So, I want to ask not about the lights themselves but about the soil and what can I do to improve their health.

I use strong fluorescent lights. I am turning them on between 6pm and 8am to provide night day. The plants like it but its not enough. The lack of sunlight seems to make them go gradually unhealthy.

Besides avoiding excessive moisture in ground, what can I do to prevent their sickness. I mean in term of soil, compost, aeration, how much to water, temperature, etc... They are mostly fragile seedlings and small tress (under a foot tall). Mulberries, eucalyptus, avocado, good king henry, bamboo, chilean mesquite, moringa, honey locust, pomegranates, siberian pea, almond. The ones that survive outdoors are much more lucky, the cold freezing temperatures put them into a state of dormancy.

Does anyone has experience with this, with long dark winters and overwintering plants indoors?

How much should I leave the soil to dry?
How much temperature it should be in the greenhouse? (Temp is easily regulated, we have cheap geothermal heating)

it is possible to overwinter plants indoor and indeed grow them from seed to harvest under artificial lights, depending on your situation you either want HPS lights or LED
HPS lights penetrate much better so if you have a plant growing vertically or anything then this is your best bet
LED lights are quite bright and dont use much energy or produce any heat to speak off, some plants can grow right into an LED and have no issues but LED lights dont penetrate so well and so LED lights work best for flat, groundcover plants

if you are willing to look past what they are growing, marijuana growers have more experience than i do with growing plants indoors and visiting MJ growing forums may give you the best answer you can get online being that they grow plants indoors completely on artificial lights out of neccessity of not allowing the plant to be seen, i recommend the grasscity forums if you choose to go that route for finding out specifics - they can tell you everything from light cycles to specific UV ranges that cannabis likes most, which can give you a general understanding to base your plant growth off of for good plant growth

i would also suggest some kind of reflective material near the plants, some people use a white wall and some use mylar or some similarly high reflective material

i only ever use lights for sprouts and may use one for oyster and shitake mushrooms this year but have little persoanl experience of using artificial lighting for growing plants

It seems to me that it is more complicate to overwinter these nice perennial vegetables and fruits, than to grow weed.

But thank you for the tip anyways. I am using a few strong fluorescent lights. It seems it is enough for some plants like crambe and tomatoes, but not enough for the eucalyptus or the good king henry or the quinoa or the honey locust. The plants seem to be suffering. The leaves are becoming with patches of light green or patches of discolored green. I do not know whether this is lack of light, too much moisture, whether it is a sign of dormancy or whether they lack some nutrition.

Perhaps I should try one HPS light but I am concerned of the danger of overheating due to leave the lamp on when I am sleeping or out working. They create so much heat.

Would the mulberry drop its leaves while indoors?

Do you think spraying with liquid compost or seaweed is a good idea?
What about repotting them in a sandy mix, to increase protection from excessive moisture?
And should I keep the growing room with a nice temperature (around 20ºC) or a little bit on the cold side (more like 15ºC)?

Everything that can help is welcome I even take sometimes the plants with me to work, to put them on a sunny window I have there. Its becoming too much work to keep these tree seedlings alive.

Devon Olsen wrote:it is possible to overwinter plants indoor and indeed grow them from seed to harvest under artificial lights, depending on your situation you either want HPS lights or LED
HPS lights penetrate much better so if you have a plant growing vertically or anything then this is your best bet
LED lights are quite bright and dont use much energy or produce any heat to speak off, some plants can grow right into an LED and have no issues but LED lights dont penetrate so well and so LED lights work best for flat, groundcover plants

if you are willing to look past what they are growing, marijuana growers have more experience than i do with growing plants indoors and visiting MJ growing forums may give you the best answer you can get online being that they grow plants indoors completely on artificial lights out of neccessity of not allowing the plant to be seen, i recommend the grasscity forums if you choose to go that route for finding out specifics - they can tell you everything from light cycles to specific UV ranges that cannabis likes most, which can give you a general understanding to base your plant growth off of for good plant growth

i would also suggest some kind of reflective material near the plants, some people use a white wall and some use mylar or some similarly high reflective material

i only ever use lights for sprouts and may use one for oyster and shitake mushrooms this year but have little persoanl experience of using artificial lighting for growing plants

well i think you may be right about it being harder, however it may be that it is simply DIFFERENT

splotches... im definately not an expert but i would try soil amendments for nutrition - so seaweed would be great for that and then i would look for lacking colors in the light spectrum - though i have no idea how to check for what color that would be...

as for temperature im not sure on that either, i would suggest looking up what temperatures each plant likes best and try for something that each plant can live with:)

sorry i cant be of more help, i know it can be difficult dealing with short winter days (though my winter days are much longer than your's it seems)

for different colors though from my understanding LED lights are easy to customize by combining red, blue, and green lights toghether on the same "ballast" if you could call ti that, or having a few seperate lights of that color

you could try introducing one of those three that you THINK MAY be the color its lacking, such as red or green and see how the plants respond...

If you are only trying to overwinter them so that you can plant them out in the spring again, perhaps it would be more economical to mimic the plant's natural winter conditions. In other words, instead if trying to keep them growing like it was summer, attempt to make them hibernate. You could run a full spectrum light for eight hours a day in a cool 45-50F green house and keep the watering to a minimum (barely moist). In this configuration the plants will not need as much nutrient or attention. Some plants need a cool season to maintain healthy growth in the next year anyway. In any case the florescent light isn't providing the proper light spectrum so the plants aren't able to make use of the nutrient in the soil. That might be part of your discoloration issue.

Thanks for your highly useful reply.

You have made a very good point. Perhaps I should try them hibernate them at cool temperatures, but without submitting them to the crazy weather outdoors, of many hard freezes and sudden thaws for the next 8 months. Only really hardy plants survive, and since I have these in seedling stage I am afraid of trying that.

I think this will depend to each species. The bamboo, crambe, almond, silverberry, good king henry and mulberry (its a morus nigra) are probably not hardy enough to stand my zone 6 freezes. So I guess a cold greenhouse is my best choice (the 45-50°F/ 5-10°C you suggested). However, I have several seedlings of mulberry, so planted some outdoors to see if they overwinter here. The others, I only have one seedling of each, so I don´t want to take many risks. But if I lose plants, I always have some seed left for next spring.

Then, I have some subtropical and tropical species. Those I might leave inside my house. My most complicate choices are the honey locust, eucalyptus, the moringa and the chilean mesquite. Because these enjoy a warm, dry weather, and plenty sunlight, its probably the ones I will retain indoors, in warm room and plenty artificial lighting. The moringa also drop its leaves down, but so far it is alive. I will try to keep them in a dry soil. I also have a yacon but its not the first time I will overwinter it; it is ok if the root is in tiny slighly humid and cool soil.

I have ginger, turmeric and galangal and these seem still very happy indoors. It makes sense because they are subtropical species that grow in the shade!

The avocado is always a gamble to overwinter in Iceland. Last winter I lost my only plant and probably its going to be the same thing this year. If I have more individuals, then I am going to try at different temperatures and see which ones do better.

Outdoors I let many cold hardy species: walking onions, asparagus, apples, skirret, serviceberry, perennial broccoli and many seeds for cold stratisfication.

Long term plan for these perennials is to move them one day to Portugal and plant them there for a future forest garden. But as "best time to plant a tree was yesterday", I decided to already be growing my future trees, even if I am in Iceland.

Thank you for your advices.

Craig Dobbelyu wrote:If you are only trying to overwinter them so that you can plant them out in the spring again, perhaps it would be more economical to mimic the plant's natural winter conditions. In other words, instead if trying to keep them growing like it was summer, attempt to make them hibernate. You could run a full spectrum light for eight hours a day in a cool 45-50F green house and keep the watering to a minimum (barely moist). In this configuration the plants will not need as much nutrient or attention. Some plants need a cool season to maintain healthy growth in the next year anyway. In any case the florescent light isn't providing the proper light spectrum so the plants aren't able to make use of the nutrient in the soil. That might be part of your discoloration issue.

Most professional growers using fluorescent tubes for plant lighting will run the lights for 18 hours a day. You have to use the 40 watt tubes. The normal cool white works fine unless you are trying to get something to flower. The tubes must be 2 - 6" (5 - 15 cm) above the plant canopy to get enough light intensity. The T-5 tubes are the most efficient tubes out there. Better to have a night time temperature lower than the day time temperature to help keep the plants compact.

When a plant does not get enough light, it tends to make smaller leaves and longer stems (etoliation.) Lack of light does not tend to cause interveinal chlorosis (patches of yellow between green veins on the leaves.) Chlorosis is a nutrient deficiency that can have many causes. Could be lack of magnesium, a lack of calcium that influences magnesium uptake, excess salt buildup in the soil, lack of nitrogen, etc. If the plant is yellow everywhere, it's getting so little light it's unable to make chlorophyll.

Unless it's a plant that really likes to be wet all the time, it's best to let the top of the soil dry down in the pot before watering again. Thorough but less frequent watering is key to preventing root rots.

Importing plant material from Iceland to Portugal may require a phytosanitary certificate that might be impossible for a home grower to obtain. Bringing seed with you would likely be no problem.

I have a lot of my perennial plants indoors. Regardless of soil type, artificial lights or natural lights, some plants indoors do suffer a lot during winter. Providing nutrients like in form of seaweed doesn't change a thing. Control of moisture, ideal draining soil mixes: nothing works. It seems it is impossible to grow some plants indoors during winter, in Iceland, due to low natural sunlight.

These are mainly the nitrogen fixing legume family (peanuts, pigeon peas, honey locust, but not the jícama, laburnum or common beans). They all show yellowing of the leaves, becoming pale, while keeping the veins green. Eventually the leaves become burnt and then the plant dies. The other family that also shows this is the chenopodium family: good king henry, quinoa, amaranth, etc.. they grow well in summer but not now. Also, the seedlings I have of crambe and sea buckthorn keep dying, no matter what I do. My moringa also drops its leaves as if waiting for the summertime.

I think these plants sense the winter season (even within the greenhouse, with artificial light and temperature), and we cannot cheat them, by providing artificial warmth and light. But as many of these cannot survive the Icelandic winter nor crop during the short summer, I am obliged to keep them inside a greenhouse. But obviously they do not do well.

Perhaps plants do sense the winter and feel the need to have a dormant season.