I dream of hostas with a snail free leaf

Hostas have been preoccupying me for the past fortnight. First up, Mark and I volunteered to take a workshop on the topic during our recent festival and were a little taken aback at how many people turned up to hear our pearls of wisdom on the topic. And secondly, I have spent this week dividing and repotting hostas in the nursery. I have reached the point where I even dream about them which may be a sad commentary on the state of my life at the moment. But there are probably worse subjects to dream about than hostas.

When we used to sell plants by mail order, we were often surprised by the number of people who fail to understand that hostas are deciduous – in other words they disappear underground in autumn to re-emerge in all their glory in spring. And it is all that fresh spring growth which is their greatest appeal. That and their endearing tolerance of shaded conditions, even dry shade.

The worst example of hosta ignorance came from a new customer in Auckland. We despatched her order by courier in late autumn and she faxed back to say that the carton had arrived and all the plants were in excellent order, bar the hostas. I can still recall her words: “It appears there has been a rabbit in the carton eating the hosta foliage. Or if the hostas are meant to be like this, then I don’t want them.” I can not remember how we resolved the situation but I am pretty certain we never sent her another plant list. Some customers, as Mark has been known to observe, put the cuss into the word customer.

As with most other plant genus, hosta aficionados like to search out the new or the different (and in the hosta world, new does not always equal visibly different) so a full hosta collection can become rather large. But we are tending the other way and weeding out varieties which have minor variations at best. In fact I find it impossible to tell the difference between Patriot (itself a sport of Francee) and Minute Man. All three varieties are green with a white edge and googling hostas throws up a host of other minor variations of the same original plant. Hostas are not all stable in type and some varieties tend to throw up what are known as sports – aberrations or variations. Occasionally it will be something worth having but that is rare… The flip side of the coin is that the variegated hostas can tend to revert to a plain colour and that reverted part of the clump will often be stronger growing so will take over in time. So if you have a fancy hosta with a plain section, it pays to cut out that reversion. As most of the newer varieties in this country have come in as tissue cultured plantlets (in other words they have not been divided from an established clump but have been increased in a laboratory from cell divisions and grown on agar), the problem of reversions is becoming more common. Tissue culture is not always stable and can throw up variations or reversions.

The most common mistake made by less experienced gardeners is to be seduced by all the wacky variegations and to plant them together – the green with white edging, the reverse variegation of white with a green edging, the blue and yellow both ways and the green and gold options. After all, who wants to buy a plain coloured hosta, especially if it is plain green or a low key blue toned one? My rule of thumb is that every variegated hosta needs at least two plain coloured ones to set it off. So a showy big blue hosta with a yellow edging is going to look a great deal more effective if it is grouped with a small plain yellow and a mid sized plain blue plant. It is the variation in size, leaf shape and some level of restraint in combining patterned leaves which makes a hosta patch pleasing to the eye.

If you can’t bring yourself to buy plainer hostas and nobody is offering you divisions, raise seed. No matter what parent plant you collect the seed from, the vast majority of offspring will return to plain colours, mostly green.

Hostas are predominantly for shady areas of your garden. They are tolerant of very dry shade under trees but equally they will be happy in damper areas with heavy soils. What they don’t like are light soils in full sun – their foliage will just burn and the plants will fail to thrive. You can get away with reasonable light levels on the margins of sunny areas but the paler variegations (the plants with white or pale yellows) will burn and crisp around the edges in direct sun.

The greatest problem with growing good hostas, as every gardener knows, is slugs and snails which feed voraciously on the leaves. I spoke to many garden visitors, particularly from Auckland and Hamilton, who talked about walking out at night and crunching their way across snails and I can remember seeing the phenomenon once in Palmerston North where it was like a horror movie (The Invasion of the Snails, perhaps, or Snails’ Revenge) with literally hundreds of them teaming across a concrete pathway. If you have a snail problem of this magnitude, forget growing anything that is snail fodder. But if you have only a moderate issue with these herbivores, a combination of good selection and good management can keep the problem within manageable bounds. Choose hostas with thicker, tougher leaves rather than the soft and wispy types. Slimy crawlers do not appear to like slithering over gritty surfaces so circling plants with sand, sawdust, baker’s bran or similar will often deflect them elsewhere. We have little problem under our rimu trees with the thick carpet of rimu needles. Yes you can use slug bait, but it is not very nice stuff and can poison dogs, hedgehogs and birds so be very sparing – one bait per plant is all that is required. If you head out with a torch on a misty or rainy night after a dry period, you will often find the hungry offenders on the move.

Given that every discussion about hostas comes down to slug and snail control in the end, I leave you with the thought that most of the slugs in this country and all of our icky snails must have come in on plant material. What I do not understand is why, on those early boats bringing settlers to New Zealand along with all their trappings to remind them of home (blackbirds, thrushes, sparrows, trees and plants), they did not usefully employ themselves on the long sea voyage exercising digital control to ensure that not a single pesky slug or snail survived. It would have saved us a great deal of trouble in the garden.