Growing hostas in pots: minis to maxis
Why not grow hostas in pots? Here are some advantages:
You can grow hostas where soil is poor, or even absent (on a patio, deck, or driveway).
You can rearrange hostas with the season, without digging.
Hostas in containers constitute numerous divisions in a Hosta Show.
Many younger hostas, and miniature hostas, will appreciate growing in ideal conditions without root competition.
On the other hand, hostas in pots need some extra care, especially during winter. Even with the best care, you will lose a hosta from time to time, but by following some basics you can keep losses to a minimum.
Here are some basics for growing hostas in pots.
First, if you are choosing a decorator pot (not just growing in nursery pots), make sure it is frost-proof. Even the best ceramic pots may break eventually, but you don't want to make it a given. If you are going to move it for winter (see below), make sure the full pot won’t be too heavy for you. You can always fit a good-quality platic nursery pot into a ceramic pot and move them separately, if you need to. Don't plant hostas in pots that are too big, but there should be room for roots. Roughly, it should be at least half as deep as the hosta mound will be tall. And make sure that the pot has good drainage. Drill extra holes if you need to.
H. ‘Blue Mouse Ears and friends in a shallow cement urn.
A common way to grow mini hostas is in hypertufa troughs. This is a porous concrete mixture, usually lightened with peat moss. If properly cared for, these can last for years.
Note that in any case, you will want to make sure that your container, once in place, can drain easily. Don't set them right on the ground, as the drain holes will quickly plug. You can find attractive pot feet, or set them on inexpensive paving stones.
Second, use a well-draining potting mix. There is a lot that can be said about this. Many growers, in larger pots, will use a mix that contains a lot of pine bark fines (a fine-grind mulch, really). You may even find a “nursery mix" at the garden center, but you can add pine bark fines to a commercial potting soil. Note that this material breaks down fairly quickly, so you'll have to repot more frequently. Another recommendation is to use commercial potting soil mixed with poultry grit, about 3:1 by volume. You may have to go to a farm/feed store to find some; the grade of grit really doesn't matter. However, this is heavier than the potting soil you're used to, so it does make the pots heavier. This isn't usually a concern in smaller pots, as for minis. Other DVHS people like to use the Organic Mechanics potting mix, which is based on grain hulls, and so is both light and quick-draining.
Do note that potting mixes with "moisture crystals" (or whatever they might call these water-retaining polymers) are not recommended for hostas, as they can contribute to rot during the winter. If you do use that in pots for planting annuals, try not to mix it in with what you use for hostas or other over-wintering perennials.
Once you have selected your hosta(s), pot and potting mix, put some kind of open mesh across the bottom drain holes, to limit how much potting mix leaks out. (I have used the plastic mesh sacks you might get in buying onions.) Partially fill the container and place your hostas as you would typically plant in a pot, being sure to untangle the roots and spread them out in the pot. If you're creating a miniature garden (sometimes called a trough garden), use your creativity. You can also include some companion plants, choosing ones that will have the same winter needs as the hostas.
The downside to a quick-draining soil mix is that you must not neglect the watering! Water the plants in well after planting, then water frequently during the growing season, every day or two during hot periods. Fertilize lightly, even if you don't routinely fertilize your in-ground hostas, but stop by mid-August to let the plants head for their winter nap.
Hostas and coleus, planted in ceramic pots.
Come winter, you will have some work to do. The hostas will go dormant, perhaps sooner than those planted in your garden. Don’t worry; you'll probably find they come up a little earlier in spring. Once the plants are dormant, they need almost NO water. It is very important that the containers not get water-logged during winter, when freezing temperatures are likely. Remember that hostas require a cold dormancy period, generally about 30 days of temperatures below 40 °F. This means that your basement is likely far too warm. Ideally, move your containers to an unheated shed or garage. Less ideally, move them to a protected location outside, and cover them with a good blanket of leaves or even a white plastic sheet. If your plants are in nursery pots, some gardeners will lay them on their sides before covering with leaves. Remember: cold is not the enemy, water is. And, it must be said, so are critters: voles just love to find your hosta pots and stay fat and happy all winter eating through them. If your plants are inside a shed, it's easier to protect from rodents. Do note, though, that such winter storage means all your companion plants must also go dormant, able to survive several months in the dark.
During winter, if there is an extended warm spell where temperatures will be above 50 °F for a few days, you can water the pots, making sure they'll be pretty dry before freezing temperatures return. If you have snow piles around and know the temps are climbing, put a handful of snow on the pot. Not enough to cover, just enough to seep in as it melts. Keep an eye out for invasion by voles, using poison bait if you must.
When temperatures warm in spring, you can resume gentle watering until the plants break ground. Protect the emerging plants, if you can, from spring freezes, since your container hostas will likely be up before those in your garden. Watch for signs of crown rot, which is more likely to be a problem with your larger plants than with your minis. Be a little stingy with water at first, until the plants are leafing out.
One last point: when should you repot? You will find that the potting soil, especially if you have added soil conditioners, will break down over time. In most cases you will need to repot about every three years, perhaps less if your hostas grow vigorously or need some special care. Often you can simply lift the plant from the pot and put fresh potting mix beneath, but do consider a complete refresh of the mix, bare-rooting your hosta (dividing if needed) and repotting. This will give you an opportunity to redesign your troughs if you have multiple plants in one container.
Enjoy your hosta containers!