Thoughts August, 2015
Driving alone across Iowa last month, observing all that glorious corn, nurtured by the richest soil in the world, I began to wonder, do hostas really grow better in the ground? I was returning home in a most circuitous route, like Columbus going west to the East, having just seen the magnificent hostas in the gardens in the Dubuque area. Of all the places I see hostas; I think they impress me most in Iowa.
Not all the soil in Iowa of course is the richest in the world. The richest soils are in the northern half of the center of the state in what is called the Des Moines Lobe. When the settlers first plowed the prairie there the topsoil was 14-16” deep! The best soils for corn are found in this area as shown on this internet map, http://agron-www.agron.iastate.edu/Courses/agron212/Readings/CSR.htm, just scroll down to the full color map. (The soils in the Dubuque area are of a different less fertile soil type, but don’t tell that to the hostas there.)
There is more to growing corn, and for that matter hostas, than nutrient rich soil. Sunlight, temperature, and rainfall are major players in the game also. I was surprised to discover that on average this major corn producing belt receives just 30 inches of rain a year, give or take an inch depending on the county. By comparison we have a whopping 42 inches here in my neighborhood of North Carolina, and that is one of the lowest totals for our state.
By the way, where did the recommendation that gardens need an inch of rain a week come from? I think it has something to do with preserving a lawn, a fairly artificial situation. Almost no garden however receives that much annual rainfall. Thus, irrigation has become an essential part of gardening today as it really has all through history back to the Mesopotamians and maybe beyond.
But I digress… So do hostas really grow better in soil than in containers? They do grow bigger, at least in Iowa and several other Midwestern states. I think a lot of the reason is their good prairie soils. It is probably not their abundant rainfall amounts, although we did hear about all the floods this spring and hostas do seem to enjoy having their feet wet. The prairie is fairly dry really especially the further west you head toward the Rockies.
I believe temperature may have a lot to do with it, also. Cool nights, even in summer keep the soil temperatures down as well as cool Iowan hostas from leaf tip to crown. Yes, it can get hot on the prairie, but it rarely lasts more than a couple of days at least until August. We about froze to death in Dubuque, with Saturday being cloudy, rainy with temps in the low 60’s!
Finally, the long days provide lots of relatively low intensity sunlight so that hostas can be grown to perfection in nearly full sun conditions. Lots of light makes for lots of hosta leaves and lots of hosta shoots, making large clumps. And if it happens to be rainy on top of that in May and June the extra water and reduced light because of the clouds will make those hosta leaves swell and those hosta petioles stretch heavenward. The right light, ample water, and rich soil in a cool temperature range will produce large hosta clumps that we Southerners can only fantasize about.
(That was July and now August has turned hot and dry. Those big hosta clumps are screaming for water and everyone is lugging hoses in the heat. Fortunately, September is right around the corner and in Iowa, thoughts of winter begin with the college football season.)
In the South, and many other parts of the country also, however, the soil is not always our friend. We are known for our red clay but we have plenty of sandy soils, too. Our soils seem particularly good at growing trees, pines followed by hardwoods in succession. Our long hot summers require us to grow our hostas under those trees to keep them cool in June, July, and even August some years. Over time we find that the very trees we thought were our partners in protecting our hostas turn out to be selfish opportunists, stealing precious water and the costly slow release fertilizer for themselves. They fill the soil with so many roots that it is almost impossible to penetrate it with a shovel.
In our heat our soils rapidly lose the organic matter with which we amended them and the strong thunderstorms of summer compact the soil to the point where all that needed rain just runs down the hill. Oh, to live on the prairie.
Now in the nursery, I can certainly turn little hostas into big hostas faster than gardeners can in their shady tree filled gardens. I can grow a pretty big hosta in a very small pot, but I do not use soil at all. It is really soil media, or potting mix, a combination of organic and inorganic materials that allows for extensive root growth free from competition. It drains well, has lots of air spaces and holds moisture. I do make it sound a little magical, well, maybe it is.
We use a pine bark mix that is now supplemented by some small wood chips. I do not like the chips but for sustainability’s sake it does reduce the amount of pure bark used. We also have some granite fines, small rocks a little smaller that chicken grit added, about 10-15%. Then we raise the pH to about 5.6 with lime. There is no soil.
The mix is a little “green” when it arrives but after a couple of weeks it calms down and accepts the water readily. Its shelf life in the pot is about a year and a half. After that time the particle size decreases as the bark decays and it does not absorb water as well as it initially did and also does not drain as well either. The pH also becomes more acid heading down toward 4.0. At that level the plant is unable to absorb the nutrients it needs and languishes. So you see, for a while my bark mix is the perfect growing media for hostas but not forever.
The ultimate solution for growing great hostas for years and years may be somewhere between a pot of bark mix in a nursery and a tree filled garden. Those of you who attended the AHS Convention in Raleigh this June, surely remember Peggy Titus’ garden with the wonderful large pond and the Tea House. The large hostas that surrounded the patio area were spectacular because of their maturity and seemingly freedom from tree roots. Yes, a large tree had died nearby allowing more light into the area but the trick is that those hostas were actually in a pot, of sorts. They were in a large planter with amended soil and concrete between them and the nearby trees.
Raised beds provide the same ideal hosta habitat but only for at most five years and by then the trees have filled the bed with their roots. Reworking the bed recreates that favorable habitat but this time the trees know their way in and the hostas start to suffer in maybe three years.
Containers planted in the garden, pot in pot, or scattered around on top of the soil will grow great hostas too. A potting mix that might include bark, compost, grit and maybe one third native soil works well but somehow the pots always dry out faster than the soil beneath them. In drought the hostas can become stressed in the time it takes for you to visit Grandma over the weekend or attend a hosta gathering in the next state. Hostas love pots but I think they like to stretch out their roots in black Iowa soil more.
Planters are perfect. They keep the tree roots permanently at bay and stay moist with their depth of 2-3 feet. They bring the hostas to eyelevel or maybe even over your head if the slope is steep. And they can be filled with real soil, not a peat or bark mix. It is the best of both worlds.
I’m totally on board, now I just need to hire a mason and find a way to truck about 20 yards of that rich black Iowa soil back to North Carolina.
There is nothing better than walking into a garden in Iowa and seeing a sea of large yellow, green, and blue lily pad round leaves. In July, they are topped by near white flowers and fresh seed pods, getting fat in the summer sun.
There is forest out on the prairie, hardwoods and even dogwood, but the hostas seem to flourish best in lots of light. The leaves might be a little scorched from a hot weekend in late June but somehow it does not matter. There are still plenty of leaves good enough to win blue ribbons at the Midwest Regional Hosta Show.
Northern gardens are filled with a large assortment of the H. sieboldiana clan of hostas. The yellow ones, grandchildren and great grandchildren of ‘Frances Williams’, that are almost impossible to grow in the South, always steal the show. Their leaves are more cupped and puckered in the sunny gardens of Iowa than elsewhere it seems and their flowers more abundant. Ed Schulz has a garden full of these beauties, one after the other. Many are seedlings of his with names like ‘Honey Brickle’, ‘Lime Ripple’ and ‘Ohh! Charlotte’. I drooled over that last one on this year’s visit to his garden.
“Sieboldianas” are the archetypical hosta, the one we see when we close our eyes and think hosta. Look up hosta in the encyclopedia and there is a photo of one. Unlike any other hostas they and their children grab our attention with their big round leaves. I believe even ‘Sum and Substance’ is a cousin of theirs, where do you think those round leaves and puckers came from? Hostadom would be a far, far poorer place without their presence; they are the backbone of any hosta garden.
And they produce lots of big fat seeds. The bees love their flowers and even if you are not inclined to cross pollinate “Sieboldianas” will produce plenty of seed on their own. The seedlings usually do not fall to far from the clump, literally and genetically. Seedlings will appear in the spring around your big clumps if you do not cut the flower scapes in the fall and most of them will favor their mother in most every way. I think the bees have little other pollen to spread that early in the year so the seedlings look like H. sieboldiana types, maybe with a bit of H. montana thrown in here and there.
I suggest you grow a few. Someone once told me that they come up like beans, and I like the image that jumps into my mind when I hear that. You can grow them inside under lights like the hosta hybridizers do or just sow them in a specially prepared spot in the garden. Just work a little peat moss, no maybe a lot, into your garden soil and cover the seed with a little fine mulch. Even if you just scatter them around they will probably still come up, if some critter doesn’t carry them off for Christmas dinner.
If you grow them in the garden you will need to move them the second year or they will eat each other or any other small hostas in the vicinity. “Sieboldiana’s” triple or quadruple in size in the first few years of life. They can be aggressive weeds, so select the ones you like best and give the rest to a neighbor. Spread the magic.
I always leave Iowa with hosta envy. You folks in Michigan or Minnesota may not understand this, but those of us down South long for those waist high or higher clumps of big round yellow leaves. It may just not be in the cards but by growing them in large pots we can almost emulate the effect but it is still not the same. All is not lost however; we have our fragrant-flowered children of H. plantaginea that rule late July and August that love our gardens. It’s a taste of the tropics. Ironically, ‘Guacamole’ and all its family of great fragrant-flowered sports have H. sieboldiana in its background too. I guess you just can’t escape the influence of the “Sieboldianas”, but on the other hand, why would you want to?