Fertilizer and temperature

[janemcgary]

I usually apply soluble fertilizer to plants in my unheated bulb house now. However, we are having an unusually cold late winter: near freezing every night, and in the 40s F daytime. Many plants are in active growth, if a bit later than usual. Should I apply fertilizer now, or wait until the daytime temperatures are a bit higher? I don't use pelleted fertilizer on the container plants but have some for the garden which is designed to release slowly at cool temperatures, unlike Osmocote-type slow-release fertilizers which need higher soil temperatures than is typical in the Pacific Northwest.

[petershaw]

Hi Jane,

great question considering our lower than normal temperatures as well. I applied some diluted liquid fertilizer just yesterday to many of the plants that needed some moisture in the media. My lack of experience with these winter growers made me somewhat hesitant but I made the otherwise educated assumption that they are used to growing in winter and the water/nutrient uptake process should be fine.

I am not much of a fan of slow release fertilizers as many of them have too much ammonium.

My soluble fertilizer is "Jack's" two part from the local hydro stores - CaNO3 in one bag and all the rest in the other.

I use the same for all my cacti and succulents, at a 1/2 recommended rate.

My media also has no nutritional contribution.

[Leo]

The nitrogen source matters. Unless it's in the form of nitrite or nitrate it takes a while for soil organisms to break it down. This can take quite a while during cold weather, or much less time during warm weather.

[petershaw]

The nitrogen source matters. Unless it's in the form of nitrite or nitrate it takes a while for soil organisms to break it down. This can take quite a while during cold weather, or much less time during warm weather.

I don know of any fertilizer source with NO₂^- in it (other than when NH₄⁺ is oxidized to NO₂^-) and it would need microbes to covert it to NO₃^- anyway.

The three main sources of inorganic N found is fertilizers are Urea, Ammonium and Nitrate. Urea and Ammonium both need microbes to do the work, but ammonium can easily be taken up during cooler weather.

The main reason I prefer fertilizer formulations with nitrate forms of N is that they do not contain high amounts of P

[janemcgary]

Thanks to all for this professionally informed discussion. I just ordered a bag of Peters Dark Weather formula to use next week in the bulb house. I got it from Amazon; although there are a couple of other vendors offering it at a significantly  lower price, with Amazon Prime's free shipping (for a 25-pound parcel) it comes out to nearly the same cost, and I will get it much sooner.

[Arnold]

Jane

25 # is a lot for me to order.

I looked and didn't see anything smaller, did you?