Growing Hostas

Hostas are among the most popular perennial plants, dying down in the Autumn and coming back each year in Spring. Hostas are very easy to grow and come in a huge range of sizes from miniatures only 10cm (4”) high to giants up to 4’ high with leaves over 60cm (24”) long. Leaf shapes also vary from thin strap-like leaves to almost circular. Leaves can be smooth, corrugated, ripple-edged and/or glossy. Colours range from gold through to blue, the rarest colour in the plant kingdom, and many cultivars have striking and beautiful leaf patterns. Although hostas are known as shade loving plants, they are, in fact, shade tolerant and can grow in a variety of conditions.

Although gardeners love them most for their foliage, they also send up spikes of flowers usually shades of lavender but also purple and white. Some hosta flowers are even fragrant.

Hostas look good almost anywhere, from beds and borders to gravel gardens and rockeries. They also make marvellous container plants. Miniature hostas look wonderful in troughs, bowls and raised beds.

Hostas grow in the wild in Northeast Asia, chiefly in China, Korea and Japan. Authorities differ about how many species there are, but they grow in a range of environments from rock crevices to the edge of swamps. They were first imported and grown in Europe in the late 1700s. The plant was named in honour of the Austrian botanist Nicholas Hosta in 1812 but are also known as Funkia. This name is still used in a few countries, chiefly in Eastern Europe.

Since the 1950s the number of cultivars has increased enormously and there are now over 11,000 varieties though many of these are not available commercially. Hostas grown by breeders world-wide are registered by the American Hosta Society.

There are generally recognised to be about 40 species of hosta, though some experts put that number as low as 24 and others as high as 70. The reason for this is that several varieties of hosta, originally thought to be species, are now believed to be hybrids. Because the records of how, where and when many species of hosta were originally found are old and incomplete, it has not always been easy to verify their classification accurately.

There are around 6,500 officially registered varieties of hosta, with around 100-150 new hostas being registered each year. Additionally, there are many named but unregistered hostas. The exact number is difficult to quantify but is probably around 2,000. Of this rather large total, over 1,000 varieties of hosta are readily available to be purchased by UK retail customers. The registration process for hostas was established in 1968 (the same year that the American Hosta Society (AHS) was founded). It is overseen by the International Cultivar Registration Authority (ICRA) and was administered by the University of Minnesota until 2001 when the AHS took over the process. The main purpose of registration is to avoid confusion over the naming of hostas by ensuring that one name is assigned to one hosta with no conflict or duplication. It also provides an accurate, permanent, and publicly available record describing the main features of the plant.

Hostas enjoy a neutral to acid soil, and, like most perennial plants, like it to be rich and well drained. To give them the best start, plant in a mixture of multi-purpose compost and good garden soil, to which you should add a pinch of slow release granular fertiliser. Some organic composts such as John Innes, tend to be quite fine and can become waterlogged in winter so it’s useful to add some coir, shredded bark chippings or even pea gravel to make the compost more free draining. especially for young plants.

There’s an old saying that the best food for hostas is water, water, water. Although hostas are very forgiving if you go on holiday during a hot spell, they will grow fastest if regularly watered – even when it’s raining! The leaves of hostas form a natural umbrella and it’s quite common to find the soil under a hosta still dry even after a few hours of rain.

Unless listed as ‘sun-tolerant’, hostas should be planted where they are likely to be in shade during the hottest part of the day. Morning sun is beneficial to most hostas, especially those with a lot of white in their leaves, which will not always grow well in too much shade e.g., H. Fire and Ice. Sun won’t kill a Hosta, but the thin-leaved varieties may burn in hot sun. Bright sun will also change the colours of some hostas (e.g., turning blue to blue-green and cream to white.) Some thin-leaved gold and lime-green hostas, e.g., H. Cherry Tart, H. Curly Fries, H. Fire Island, will also bleach out and are best in shade.

Hostas are one of the most attractive foliage plants for growing in pots and containers, whether on a patio, on garden steps or even in your garden itself – particularly useful if planting in dry areas under trees. Planting in containers can help to reduce slug and snail damage since there are usually other things for them to eat that are easier to reach.

To help prevent damage in pots, place a piece of porous landscape fabric or woven windbreak netting in the base of the container so that slugs cannot access the plant through the drainage hole. A further preventive measure is to place pots in a saucer. Keeping it topped up will not only make sure the hosta has plenty to drink but will also make it harder for slugs and snails to climb the pot since they can’t swim!

Hostas can be re-potted when their roots grow out through the bottom of their pot. Check your potted hostas every 2-3 years to make sure they are not pot-bound. If the hosta can’t be shaken out of its pot, you can use an old saw to loosen it. If you don’t want to re-pot into a bigger pot, you can either divide the hosta or root-prune it. This means removing an inch or two of root from the base of the plant, and even the sides if it is really pot-bound. Replace in the pot with fresh compost. The best time to do this is at the start of the growing season, March-May.

Slug and snail damage can be reduced or even eradicated using nematodes, poisoned bait (slug pellets) and barriers.
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Hostas take between 4-8 years to grow into a mature plant, depending on the variety. Hostas can be divided as soon as there are multiple ‘eyes’ (little buds) around the crown of the plant. These can often be felt just under the surface of the soil but be careful not to break them off with a searching finger! Some slow-growing varieties may take three years or more to reach this stage. Others may be dividable in no more than a year.

To divide a large mature hosta, it’s best to wait until spring when you are not battling with too much foliage and can see the new leaf buds. Loosen it from the soil as much as you can with a garden fork and then cut partly through the crown with an old saw rather than trying to cut or chop it with a spade. This minimises root damage. A very old hosta can be cut into several new plants – take the new plants from around the crown. If there are few buds in the centre of the plant, it means the crown has grown so woody, nutrients aren’t able to get through to the leaves. In this case, it’s best to discard the central crown.

Smaller or younger plants can be dug up or removed from their container, hosed around the crown to reveal the eyes and then divided with a bread knife. Eyes may not grow evenly around the plant and washing the crown means you can make sure your divisions are of equal size (similar number of eyes on each division). Again, cut through the crown and tease the roots apart.

The best time to divide is in late spring to mid-summer when growth is at its fastest. This gives the divisions time to recover the same season. The only downside to dividing in spring is the danger of damaging new shoots and leaf buds. Large, well-rooted hostas can just as safely be divided in autumn after the leaves die down. Miniature hostas are best divided from May to June.

Hostas are very hardy perennials and don’t generally require any special treatment over the winter period. In the right conditions, they can endure temperatures below -30 deg C and, provided that their roots have been allowed to grow sufficiently well to anchor them in the soil, they can withstand many freeze-thaw cycles. Ideally, hostas need a period of dormancy during winter to ensure that they are able to thrive during the subsequent season; that is, about a month of daytime temperatures below 5 deg C.

Some miniature varieties are less forgiving of cold, wet soil and poor drainage. This can sometimes be an issue for minis in small containers; if their root-ball freezes and then they are watered, the frozen root ball may prevent adequate drainage causing the plant to rot. Whilst this is far from a common occurrence, some people like to over-winter their pot-grown mini hostas in an unheated garage or greenhouse where they can control the watering or alternatively sit the pots on their side during winter.

Hostas (apart from H. ventricose) do not come true from seed. The fun and excitement of crossing two hosta species or hybrids together is in creating a genuinely new plant and not knowing exactly which characteristics it will have. There is always a possibility of producing a new, truly garden-worthy plant, even though most seedlings may be green.
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Most hostas thrive best in morning sun and afternoon shade. However, many hostas will tolerate full sun (six hours or more a day) if watered well and mulched. In sun hosta colours often change. Blues may become green-blue and gold centres and leaf edges may become much paler, even turning to cream or white as the leaves age. For a list of some sun-tolerant hostas
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Hostas are generally disease and pest free. Apart from slug and snail damage Read more…there are few problems to look out for.

Hosta Virus X As the name suggests this is a virus disease and shows itself through blotchy mottling of leaves and discolouration along the leaf veins. If a plant is affected, it may not show up for years. Some varieties are known to be particularly susceptible to this virus. These include some popular hostas such as H. Gold Standard, H. Gypsy Rose and H. Sum and Substance. The virus is passed on by transfer of sap from an infected plant to another. If you find a hosta suffering from Hosta Virus X it should be destroyed. The chances of finding Hosta Virus X among your collection can be reduced by always buying from specialist suppliers.

Vine Weevil Vine Weevils can occasionally be troublesome, both in container and garden grown hostas. The adult beetles bite semi-circular notches out of leaf edges, whilst the fat, maggot-like larvae eat the roots. The adult weevils are, like Lily Beetles, very difficult to eradicate except by finding and killing them. The grey-black weevils are night-feeders so may be seen whilst searching for slugs and snails with a torch, although they seem to prefer dry nights to wet ones. They tend to drop off a leaf at the slightest movement so catching them between finger and thumb seems to work best. Or you can try to catch them in a container as they fall.

The most effective solution to the problem is to apply vine weevil nematodes, available through Amazon and other on-line garden retailers.  Garden centres tend not to stock them because they need to be kept refrigerated until use and the ‘use-by’ date is very short.’

Liquid Vine Weevil killer can be bought at most large garden centres but is not effective against adult weevils. Container grown plants can be protected by using horticultural or alpine grit as a top dressing/mulch.  This deters the weevils from laying their eggs in the pot. Other perennials are susceptible to vine weevils – particularly heucheras.

Miniature hostas have an undeserved reputation for being difficult to grow but most varieties of miniature and very small hostas are as easy to grow as their larger relatives.
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The ‘catch-all’ term for this change is ‘Reversion’. This means a hosta ‘reverting’ to one of its solid colour ancestors. Virtually all variegated hostas are cultivars and at some point in their ancestry were unvariegated.

Occasional ‘reversion’ is common to many varieties of hosta and some varieties are more prone to it than others. Most often it will just be one or two eyes (leaf buds) that revert. In extreme cases the whole plant may lose its variegation.

However, the green or blue leaves may not be a true reversion. If a variegated hosta produces blue or green leaves it may be a ‘sport’, a mutation or new variety. The hosta may simply be helping itself to survive. A green or blue plant contains more chlorophyll and tends to be more vigorous than a variegated plant. A blue hosta, incidentally, is still a green hosta.  The ‘blue’ coloration is a waxy coating on the green leaf that reflects blue light.

What to do about ‘Reversion’
If the problem is just occasional reverted leaves, then all you need to do is to remove them at the base of the plant. If, however, you trace the leaves down to their base and find a whole shoot or section of the plant has turned green or blue, then you will need to cut out the piece, including its crown and roots. If you leave the shoot, you may find that eventually the whole plant will revert and you have lost your variegated hosta.

George Schmid, author of ‘The Genus ‘Hosta’, says that all variegated cultivars will eventually lose their variegation even if it takes a human lifetime for them to do so!

There are many hostas on the market which are solid-colour sports of their parent, e.g. H. ‘Greenie Weenie Bikini’, an all-green sport of the variegated H.  ‘Teeny Weeny Bikini’. So, before you discard the affected part, check your Hosta’s parentage. This web page helps: https://www.myhostas.be/sports/index.htm 

If the ‘reversion’ is attractive and you feel it is worth saving, then you can pot-up the cut-out piece (leaves, crown, and roots) and you have a new hosta.