To fertilize or not to fertilize, that is the question

My breeders are all in pots of artificial soil made up from peat moss, cedar bark and perlite. They were last fertilized May 1 just as the breeding season got underway here. Some are looking a little chlorotic but I’m wary of fertilizing for fear of forcing hips to drop. I’m open to suggestions.

Don are you sure the chlorotic leaves are not caused by a mineral deficiency? Also the cedar bark may be depleting the nitrogen in the soil mix. Micro organisms need nitrogen in order to break down the wood. So you may need to fertilize more than you would if you where growing in straight soil. But before you rush out and fertilize wait until someone with more experience replies. But my thought is because the cedar bark you will need a little nitrogen.

Don, what has been your usual fertilization regime for these breeders in the same potting mix, in previous seasons?

Well I wouldn’t fertilize. I learned my lesson on that one, hips dropped like hot potatos. I rather keep the hips than the leaves, I don’t care what they look like as long as the cane is green and I usually remove the leaves below the hips anyway.

Don. another question…have you checked the pH of the mix?

George and Max, in the past I have fed them once a month with Peters or Miracle Grow. They get watered from the top daily unless it rains so that quickly washes out the soluble fertilizer which easily explains the chlorosis. The commercial fertilizers are pretty complete and so far I haven’t noticed signs of mineral deficiency. The pH is about 7.

I dissect each dropped hip to see if there are seeds forming and for the most part the are barren. I think I’ll just lightly feed the ones that need it most and hope for the best.

Don, I think that the answer depends on the rose seed parent. Difficult seed parents should be fertilized in early Spring and probably not be fertilized after there is a good hip set. New growth with these roses tends to cause hips to abort. For good seed parents, those that set hips readily, regular 1/4 to 1/2 strength fertilizing is good for them. Some of these will put out a good flush of another bloom cycle that you can hybridize onto while maintaining the first set of hips.

I only use good seed parents so I continue to fertilize them throughout the season.

Jim Sproul

Jim that is a good bit of information; especially since I have only heard the opposite. It has always made me wonder taking into consideration certain potting mixes or mix formulas contain very little nutrients. I myself always use a very very weak mix of fertilizer. If I had real soil I don’t think I would fertilize but that would also depend on the soil too. There are a lot of new housing developments out here were they strip all the top soil. Build a house on it and leave the subsoil which is loaded with calcium deposits and phosphorus deposits.

Don,

I give one normal dose of granular in late March/early April with a small dose of slow release in May. I really havent seen anything detrimental from this. I skip fertilizing in some years to avoid any build up, and I still didnt really notice a difference in hips. However, I am uber careful with pot culture, so I only use slow release in them. Potted plants are too easy to salt burn, especially if they dehydrate, which they are prone to do because of their physical nature. However, if you do use slow release then be sure to note that high heat can release larger amounts of fertilizer at one time, which can make this detrimental to more southern areas at the exact time when the plant could also be dehydrated from such heat – a lethal combo punch to say the least. Can you say Kentucky Fried Rose? :slight_smile: The one thing I do add to any pot culture are water crystals. Theyre cheap and fun. They mix readily into soilless media with ease. I am currently testing them for cuttings. Instead of peat or vermiculite + perlite or pumice, I am trying water crystals + pumice, lol.

Thanks Michael.

I’ve been using insulation grade perlite in my mixes which holds a lot more water than the horticultural grade while still allowing good drainage.

If all goes well we will shortly be in a real house with a real yard and I’ll be facing the decision whether to plant my roses or keep them in pots. Fried roses are a problem in Connecticut, too.