There is very little rock-solid literature on just what Hosta need in the way of mineral nutrients. There is also no consensus information on how to best apply fertilizers to them. There is not even agreement if Hosta need much in the way of fertilization. There are lots of opinions but little science. Opinions are easy to come by, but science is hard work. On the other hand, opinions are usually free.
Some ‘experts’ recommend various chemical fertilizers; some do it with granular formulations around the plant (soluble and slow release) and others with liquid solutions to the leaves or the general area. Then there are the organic ‘experts’ that champion fecal materials and rotten stuff of all kinds. Which is best – horse, cow, hog, chicken, rabbit or sheep manure? Is chopped up bark, wood, grass, or leaves the best? When is the best time to fertilize? Spring only, all summer long, every two weeks, twice a year or continuously? Can you apply to much?
Well I’m a Hosta growing scientist but like everyone else I have little scientific fact to lay on you. But like most, I do have opinions which are true gospel which I will share with you freely.
First let me say that most mulches are almost worthless as fertilizers because they contain few minerals or lease them too slowly. Leaves have no value what so ever (according to Scott researchers who I talked to in Columbus, Ohio) while grass has some nitrogen but also weed seeds. Mulches do have useful purposes and certainly are good for loosening up our Cincinnati clay soils when worked into them. Some growers swear by white pine needles. I tend to swear at any that don’t last for several years.
My grandparents were farmers. By necessity they were true organic farmers. They had chicken houses and barns to clean. My dad grew great beans and tomatoes. He loved manure. He was also prone to walking out and tossing some chemical fertilizers at them. He was right in doing this. A plant does not know where its nitrogen ions come from and cares less. An ion from an organic source is the same as one from a mineral one!
Some manures are ‘hotter’ than others. A few years ago I dumped some rabbit manure on an emerging Hosta and burnt it up. Horse manure is probably the safest to use and HSGC President Carol Kilberg has lots of it in her stables to give away.
Because no one knows the best mix of nitrogen, potassium and phosphorous, the safest bet is a balanced formula. I think a 10 -10 -10 is better than a 20 -20 -20 because you are less apt to over apply it (Bob Solberg agrees with this rational). Van Wade recommends a slow release fertilizer (18 -7-10) such as Osmocote, one time, as they emerge in early spring. Note: Scultz Mulicote (17-17-17) is cheaper than Osmocote if you can find it.
Hosta apparently do not require a whole lot of fertilizer but a bit will certainly not hurt them. Moderation, like in most things, is a good idea here until someone proves different. With that said, I probably over fertilize. How can any one starve their babies?
Solberg recommends leaf fertilizing using Miracle-Gro Tomato Plant Food (18-18-21) with micronutrients and magnesium. Sounds good to me but rather than do it every two weeks as he says, I do it twice weekly from when they come up till June. The AHS recommends not fertilizing after June when they have stopped growing but Mark Zilis says to stop 6 weeks before frost time.
Those that use an ammonium spray on their leaves to discourage slugs are also giving the plant a good dose of nitrogen. I will add 2 cup per gallon to the tomato plant food to increase its nitrogen content and zap the slugs at the same time. I broadcast a lawn fertilize over the Hosta beds in early March to help the surging sprouts to explode out of the ground. Remember-fertilizing is useless without lots of water and when Hosta stop growing, they don’t need it. Well that’s my opinion, and it was free.
Nutrients for Hosta - By Jerry Robertson
