I have many plants that are still growing, too, and will be hardy and continue to grow through the winter. What container plants do you have that are still growing in the winter with respect to your question? Usually the only solid guideline is not to fertilize (or as regularly or often) when a plant is in dormancy; thus, the answer(s) will also be plant-specific in addition to temperature and sunlight changes.

Just to give you another perspective. I don't fertilize my Veitchii (gardenia) and roses (withholding a little later than Veitchii due to blooming time) in late fall so to discourage tender growth and allow them sufficient time to harden in defense of winter cold exposure. However, I will continue to fertilize cool temperature short-term crops and some hardy or short-term ornamentals. I planted some sunflowers (annual) late this year, one just bloomed a few days ago and going strong (hopefully more to come); thus, I have to give it low-nitrogen bloom booster at this time even with the characteristic wide temperature swings (30F+ AM/PM winter temp difference) here. It's okay to fertilize the sunflower even with the changing cool temperature because it's blooming and it's an annual.

I do fert all cool weather plant thru most of the winter months. AKA pansies, snapdragons, flowering cabbages, allyssum. I do like to change out to a more nitrate form of soluable fert to avoid ammonia gas problems which can be a problem during periods of winter that is below 50 degrees regularly. Many plants if dormant won't want feeding and others sparingly. As Legacy says more specific to plants would be needed to offer more helpful ideas.
Happy Growing David

I am familiar with coastal weather and believe the plants you are referencing are NOT dormant as many plants in your weather/climate do not go dormant. If that is the case I would continue to fertilize, but reduce the amount to match the slow growth of the season. Al

I have about 100 pots or close to it. Cant name them all but do have alot of evergreen and deciduous trees. Also things like gunnera and other large leaf plants that I use for concrete leaf making. I also have lots of clematis and vines of many sorts.
I have always not fertilized in the winter. With this soil that doesnt have compost or any thing but Micromax and a crf that I put in at the beginning of summer I feel I must do something. I suppose the flowering plants dont need much as they are dorment. I guess I will do a weak 24-8-16 every month or two?

Hi, B. The fertilizer you're using is urea based and full recommended doses during cold weather (noted upthread) could cause ammonia toxicity in the plant. This is especially true in cold soils that are low in air porosity due to a reduced number of the bacteria that convert ammonium to nitrate.

Your evergreens really never go dormant and the plant will appreciate a full complement of all nutrients in the soil at all times, even if it's a weak solution. The dormant plants need no nutrient attention until onset of budswell.

Weak doses along the lines of 1/8 recommended strength will be just fine, and the blend you are using is a good choice. If you (if your soils allow you to) water copiously when you do water, there is no reason you can't fertilize more frequently than every other month.

I probably have around 125 temperate trees and I choose not to fertilize either my evergreens or the dormant deciduous. The deciduous trees fare fine w/o it and the evergreens are kept in the garage & see little light (a factor to consider) and are only watered sparingly with snow 3 or 4 times per winter.

Good luck. The Turface inquiry turned out to be another dead end.

Al

Al I wasnt sure what weak means so 1/8 of the 24-8-16 sounds right to me. I think what you are saying sounds right on.
I have faith I can find Play Ball. Have a couple sources to check out. Thanks again. B.

You're welcome. Wish I could have been of more help. ;o)

BTW I just offered another post on the fertilizing thread that you may wish to read. It gives a little more detail about ratios/ tissue content. It puts what you're using in a favorable light, too.

Take care.

Al

I have several dozen permanent containerized plantings - various trees, shrubs, perennials, etc. including most of my collection of dwarf conifers. While it is true that some of these plants are never fully dormant during the winter months, nonetheless their metabolism slows and growth is minimal, as is nutrient demand. In all my years of growing containerized plants, I've never fertilized any of them through winter and none appear worse the wear for halting this process for 4-5 months. If you've taken the time to develop a high quality container soil and have fertilized adequately through the growing season, it is my experience that winter fertilizing is unnecessary.

FWIW, our containerized nursery plants - out in the elements all winter long - are not fertilized during this period either. They get a last hit of fertilizer right about now and that's it until spring.

Although temperature drop and swings can theoretically increase the risk of ammonia and nitrite toxicity, they are not major variables that can't be checked by co-existing counter forces like significant leaching of high soluble nitrate ion, winter loss of nitrates, loss to volatilization, or as compared to other significant contributors of nitrite toxicity such as high temperature, soil acidity, and degrees of plant sensitivity to ammonium toxicity as a function of root sugar production, and etc. In fact, some found the presence of ammonium in the root zone is beneficial when the root temperatures are low but become detrimental at high root temperatures. If the chance that low temperatures and temperature swing induced ammonium toxicity argument is likely to occur, it would seem one more reason to limit the use of high nitrogen or 3:1:2 synthetic fertilizers (be they nitrate-, ammonium-, or urea-based) in containers.

In general, nutrient absorption does not occur when media temperatures are below 40F, so there is limited use to supply fertilizers when potting mix temperatures are in that range, or when the plant is not actively growing in that range of temperatures. Know your plants by consulting specific horticulture fact sheets for your region for best winter care.

The cited and excerpted reference below is not specifically for winter fertilizing of containerized clematis that you are seeking, but the cited reference or relevant excerpts from Three Requirements for Long-Lasting Clematis as prepared by Oregon State University may help other Oregonians or container gardeners growing clematis in similar USDA hardiness zones who do not adopt a regimented fertilizing program or use recommended universal fertilizers for all containers but prescribe to sustainable nursery practices:

Deciduous clematis are hardy in all Oregon climates. Evergreen varieties are more sensitive to the cold and perform best in western valleys and the coast.

... Set the plant in the hole with the crown two to three inches below the soil surface. Stake the vine until it has grown enough to reach its permanent support. A new plant should be well-watered, but not overfed. Once established, it will respond well to rose or tomato food, or any fertilizer in the range of 5-10-5 or 5-10-10.

You may find additional winter care information specific to your other container plants from this Oregon source. I didnÂt find many published container culture articles at this site, however.

Expanded shale (rock vs clay) is widely used by organic gardeners and have been researched and field tested by other states as well as several Texas universities and counties and recommended and used at the Dallas Arboretum and Botanical Society. The Dallas Arboretum also recomends 1:1 (shale and potting soil) mixture for use in large containers to increase drainage and reduce weight. It is widely available in bulk or custom blend from local nurseries or soil suppliers.

Lava rock (also widely available) is another inorganic alternative.