What is considered "spring" for fertilization, repotting, etc?

lizzie_nhJanuary 22, 2014

Quick question -

I have seen a lot of advice which mentions waiting until spring to fertilize certain house plants, or repot them, etc..

What does this really mean? Where I live, we tend to lose the last bit of snow by mid-April... occasionally a little earlier, sometimes a little later. Typically nothing is greened up or leafed out by that point. Yet spring comes much earlier in the southern regions in which many house plants would grow natively. And the conditions inside my house may be no different than the conditions inside in another much warmer zone.

So... what should I consider spring for a plant which I intend to keep inside? February? March? Later?


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Personally I never entirely stop feeding but I work with them in toasty warm offices.

In your case I'd say late March/early April.

    Bookmark   January 22, 2014 at 3:40PM
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Hi there neighbor! I'm in New Hampshire too (Wilton). I do my spring repotting and fertilization work in March to April. Although, I do feed once or twice over winter with some plants.

I have a Boston Fern that tells me when to start "waking" up everyone else in the house and studio - it starts to dramatically shed leaves in late March to April, that's when I know it thinks it's spring and wants to get back outside. It's so tough to tell it "no, it's too cold! Wait 1 more month!" (The thing is larger than I am so moving it outside daily and taking it in during the frigid spring nights isn't an option.) But that's when I start to do my "spring cleaning" with my other houseplants, almost all tropicals.

    Bookmark   January 22, 2014 at 4:35PM
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tapla (mid-MI z5b-6a)

When people give the advice that you shouldn't fertilize your plants during the winter, you can assume 1 of 3 things. 1) That they are in error 2) That they are repeating something someone else said/wrote in error 3) That they are making the assumption that everyone is using a soil that virtually ensures a steady increase in dissolved solids (salt) in the soil solution because these types of soils demand the grower waters in small sips to prevent the soil from getting soggy and remaining that way until the plant uses the excess water or it evaporates. Watering in sips guarantees that all the dissolved solids the plant doesn't use STAYS in the soil.

I think we can all agree that there is absolutely no harm in having a modest maintenance (modest) level of nutrients in the soil and available for uptake at all times. We don't want too much, and we don't want too little; maybe half the concentration that would be ideal in the summer would be just about right in the winter. If you're on the fence about whether or not you think a maintenance level of nutrients in the soil is a good/bad thing, remember that in nature, no one removes the nutrients from the soil in winter when plants are resting or dormant.

The reason you hear the advice not to fertilize in the winter is based on assumptions. The assumption you are using a soil you can't water correctly w/o risking the plant's health, and the assumption you don't know how to get around that problem. It's better if you don't have to work around the problem, but knowing how to flush the soil of accumulating salts regularly will allow you to fertilize regularly in the winter.

Let's define what goal we should be working toward when we put our nutritional supplementation program together. Then examine the easiest way to get there. The goal for fertilizing containerized plants can easily be described. You should work toward ensuring that all the nutrients plants normally secure from the soil are in the soil solution at all times, in the ratio at which the plant actually uses the nutrients, and at a concentration high enough to ensure no deficiencies yet low enough to ensure the plant isn't impeded in its ability to take up water and the nutrients dissolved in water. This goal is easily achievable using one water soluble synthetic fertilizer. You CAN use organic forms of nutrition, like fish/seaweed emulsions or various types of meal, but that makes it much more difficult to achieve the goal because you can't know how much of what is available at any given time.

There are 2 things that limit our ability to fertilize effectively during the winter. A poor soil, and a fertilizer with a ratio of nutrients significantly different than the ratio of nutrients the plant actually uses. For instance, 5-15-5 is a popular NPK formulation for houseplants, but plants use much more N than P, yet that fertilizer provides much more P than N. What happens to the extra if you can't flush it from the soil regularly? It accumulates, and 2 things happen as singular nutrients accumulate. It raises the level of salts in the soil unnecessarily, and when singular nutrients are in the soil in excess, the excess makes it difficult for the plant to take up other specific nutrients. For instance, an excess of P can cause deficiencies of zinc, magnesium, copper, calcium, potassium, and especially iron. So your iron deficiency might not really be a deficiency at all, at least in the sense there might be enough iron in the soil to satisfy the plant's needs, but the plant can't assimilate it because if the excess of P.

If you can't/don't flush the soil regularly, any dissolved solids in fertilizer solution and tapwater will continue to accumulate in the soil. As the level of salt in the soil solution increases, the ability of the plant to take up water DECREASES, and this, at a time when humidity levels are usually lower than the driest deserts (literally).

In winter, people flock to GW looking for a remedy to the spoiled foliage on their plants. Predictably, they are usually dealing with a soil that remains wet too long, and one that virtually ensures a build-up of salts in the soil. That 1-2 punch is really rough on plants any time of year, but especially in the winter when humidity is low.

I use soils that allow me to flush them at will. I can pour gallons of water through every pot, if I wish, and never worry about roots rotting or their function being impaired by lack of O2 due to soggy conditions. I also fertilize with Foliage-Pro 9-3-6 every time I water, and I've been doing that for at least 15 years, using Miracle Gro 12-4-8 or 24-8-16 before I changed to the much better Foliage-Pro.

So you can see there is a significant advantage in keeping a maintenance level of all nutrients in your soil and in a favorable ratio to each other at all times of the year. It may be necessary for some people to stop fertilizing, just so their plants will live through the winter. The choice to STOP fertilizing altogether in the winter might be the lesser of two evils, but the lesser of two evils would still be an evil.

About the repotting .... every month of the year can't be the best choice for repotting your plants. Eg, you wouldn't want to repot in winter or early spring, because plants are at their lowest energy levels of the entire growth cycle, ensuring recovery will be longer than necessary and the plant more susceptible to insects and diseases while its recovering. Fall isn't a good choice because the short days of winter also mean a longer recovery period. That leaves summer as the best time to repot and do any significant root work. The days are longer, so the plant can make more food, and the plant id genetically programmed to do most of its growing and storing of energy during the summer. Most potential for the fastest recovery is assured. I always suggest you do your repots between Father's Day and Independence Day because that's easy to remember.

I always keep in mind that they're (the collective) your plants and you can do as you please, but nature has rhythms that, if we pay attention, can be used to our advantage. Remember the old margarine commercial where Mother Nature is casting storms and lightning while admonishing, "It's not NICE to fool with Mother Nature!"? There's some truth in that. I have learned that if you work with the natural cycles of the plant and learn how to look at things from the plant's perspective, you'll soon come to an easy (comfortable) way of interacting with plants. The more time I spend with plants, the more I can see with certainty that as your knowledge and understanding of plants grows, the more rewarding the nurturing experience becomes. That would be a good thread topic for the philosophical among us. ;-)


This post was edited by tapla on Wed, Jan 22, 14 at 17:16

    Bookmark   January 22, 2014 at 5:09PM
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Thank you very much Al - especially for the lesson on fertilization, which was far better and less mystified than what I've gleamed from the gardeners at the greenhouse this past year who only carry osmocote and miracle grow so I guess they're liimited in their advice there. I'm going to look for Foliage-Pro 9-3-6. I have heard many people say never to feed over winter, but I do - just far less than in the summer.

I like the idea of soils that flush completely. New to the forums, I did try to follow the "container gardening" forums to learn more about better potting mixes, but found myself confused by the terms used in the soil mix posts. So I need to do some deeper background research.

And I was in error because I always repotted around late March to early April thinking to get them ready in time for the growing season (not that I repot every plant every year - just the one or two that need it). I'll back off until late June and see how they do. I've been lucky with repotting and changing soil in March-April with them so far, but I don't want mere luck to depict the health of my plants. :) So thanks again!

    Bookmark   January 22, 2014 at 5:26PM
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tapla (mid-MI z5b-6a)

You're welcome.

I don't want it to sound like a spring or winter repot is a death sentence. If your plants are fairly healthy, they'll tolerate quite a bit. I guess what I'm trying to do is point out that if you wait a bit to repot, until summer, you'll find your plants in 'cooperate' mode instead of their 'tolerate' mode. Keep in mind too, that there is a big difference between potting up and repotting. You can pot up any time of the year, though you should be judicious about potting up during periods of slow growth if you're using a heavy soil. If you're using a soil that allows you to water correctly w/o concern, you can pot up any time w/o worry.

I didn't realize you're new. Welcome! I hope you make lots of friends and you're able to get more from the growing experience as a result of your interactions here.

    Bookmark   January 22, 2014 at 5:56PM
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Al, thanks for such a detailed and informative post!

Your advice to report in the summer, and the explanation why, make absolute 100% logical sense to me. And yet, for some reason, no matter what plant care I google, online sources inevitably say to repot in spring. I wonder where this conventional wisdom comes from. Most of conventional wisdom is SOMETIMES right in SOME circumstances. What's the deal here? Maybe they think that because the plant is about to start pushing new growth out, let it push it out firmly into the new media rather than uprooting and disturbing new growth mid-season? Does this make any sense to you on at least some level? Or maybe the advice comes from outdoor gardening where spring is THE time to put things in the ground, and nobody thinks beyond that?

Lizzie, to come back to your title question, plants feel spring and other seasons by length of day much more than by temperatures or snow or whatever else.

Which brings me right back to a related repotting season question. If I am growing under lights, how do plants even know whether it's spring? Isn't it always then the right time to repot, as long as there is a legitimate reason and as long as the plant is strong enough?

When it comes to fertilization, I've also learned to take the advice to eliminate/reduce fertilization in winter (which I also see plenty of online) with a huge grain of salt. A good quantity of my plants are growing now in winter much more than they were growing this past summer for some reason. Taking the nutrients away now makes zero sense to me under the circumstances. Even with plants that are growing less or not at all (and remember, we only see growth above ground - they may be growing roots now), I still fertilize - for simplicity and simply because I can, with a well-draining soil like Al said.

    Bookmark   January 24, 2014 at 3:28AM
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I agree, Greentoe. That's pretty much how I learned - the ladies at the greenhouse gave me similar information and when I did research online, that was the general advice given across the board. But no explanations, no details. That's why AI's advice is something I am going to follow - it makes better sense and is explained far better than what I've been told or learned on the web. Obviously, not all sites are great to learn from, but when lots of them say the same thing, you assume you have a good handle on things - LOL.

    Bookmark   January 24, 2014 at 8:49AM
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greenman28 NorCal 7b/8a

Al's advice is excellent as always.

I note that he's discussing the plants we treat as houseplants primarily.

He'll agree that certain plants can be re-potted in the early Spring, such as maples....the trick is to re-pot them right before the buds begin to swell (when the plant is coming out of dormancy and in a quiescent period). This way, the plant barely notices a thing.

Other plants like Citrus are best re-potted in early Spring, too, between flushes of growth.


    Bookmark   January 24, 2014 at 11:10AM
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tapla (mid-MI z5b-6a)

Spring and fall are the best times to plant and transplant outdoors - 'plant' because soil temps are warming and there is plenty of moisture available - 'transplant', again because moisture levels are usually more than adequate, and most temperate plants are programmed to produce a strong flush of growth in the spring.

A large % of growers don't draw a distinct enough delineation between growing in the garden and growing in containers. There is a VERY large difference. On a scale of 1-10, with 1 being growing in the ground and 10 being full hydroponic growing, container culture rates about a 7 or 8 - much closer to hydroponics than growing in the ground. To add to that, we also have a difference in the way tropical plants grow. They tend to put on the most growth when temps are warmer and days longest.

I think it's natural for people who don't clearly see container culture as requiring an approach that differs substantially from that required to garden proficiently, to think that all plants are best repotted in the spring. As noted, a true repot, which includes root work and changing all or a large fraction of soil, is a job best attended to when energy levels are high. We also repot temperate plants when their ability to turn energy into growth is immediately before peak, so there is that parallel, but with a variance in how to best time the work.

If I am growing under lights, how do plants even know whether it's spring? Isn't it always then the right time to repot, as long as there is a legitimate reason and as long as the plant is strong enough? Phytochrome is a pigment and the light receptor responsible for helping plants determine where they are in their growth cycle. Phytochrome exists in two forms, depending on the wavelength of light absorbed. The change in the ratio of these two forms of phytochrome occurs and can be measured on a daily basis (you can look up photomorphogenesis for a better understanding).

As day length increases/decreases, the phytochrome ratio changes. The change in the ratio triggers the chemical messengers that "tell" the plant what to do and when the most appropriate time is to do it. The plant is attuned to extremely subtle changes in light wavelength, intensity, and duration.

I have 64 sq ft under fluorescent lights in my basement, which has 3 windows. 2 are covered by decks & one is behind a rod where we hang off-season clothing. At noon, in mid-summer, you could never see where you are walking in the basement without a light. It's not completely dark, but almost (at midday). Still, with that little amount of light, and my lights on a 16/8 timer, the plants know it's time to shake themselves awake in March, and start putting on some noticeable growth as we pass the vernal equinox - when the dark period becomes shorter than day length. It's actually night length that drives photomorphogenisis, not day length.

As I said, you CAN do whatever you want (almost an understatement and not said in a snotty way), but when you start to really get intimate with plants, gaining an ability to anticipate how they will be reacting in a week/ month/ or 6 months - a good understand their rhythms, you'll feel a much greater sense of being in harmony with them because you'll be working with, instead of against the natural flow of things.


    Bookmark   January 24, 2014 at 5:35PM
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Come to think of it, I once noticed that some plants on my plant stand, especially on the lower shelf, were reaching not only for the artificial light above them, but also slightly for the shady window a good several yards away. To make sure I did not see things that were not there, I rotated the plants, and a week or so later they again turned slightly toward the space sort of in-between the lights and the window.

To my eye, the fluorescent lights (T5HOs, 4 bulbs x 54W) are so much brighter, but plants do not detect the same light spectrum that humans see, so I guess even very weak sunlight does the thing it's supposed to do.

    Bookmark   January 27, 2014 at 8:10AM
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tapla (mid-MI z5b-6a)

Keep your lights toward the blue end of the spectrum for indoor growing best results. 5100K or 6500K would be best. If you have enough light that o/a health isn't a problem, you'll want to be a little closer to the red end if bloom induction is a goal.


    Bookmark   January 27, 2014 at 2:50PM
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Mine are all 6500K. I did ponder the idea of getting maybe one 3000K tube for flowering, but was dissuaded on the "growing under lights" forum.

Although now I feel like I am transitioning from growing a bunch of whatever the hell looked pretty when I went to Lowes that day two years ago to being a little more selective and focusing on hoyas and maybe (gasp!) orchids. Both flower, or at least that's the goal, so I may reconsider my light spectrum choices going forward.

    Bookmark   January 28, 2014 at 2:46AM
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