Hosta and Slug Damage

(slug damage on Hosta courtesy of University of Illinois Extenstion)

Question:
Should I remove the faded flowers from my hostas?

By August many of my hostas have tiny holes, I assume from some sort of bug or spider. I noticed this year that my new hostas in an area that in not watered as frequently are free from these "holes". Should I water less or do you have a suggestion for what to spray my plants with? It's mostly on the green/white varigated hosta.

Answer:
You can definitely remove the faded flowers from your Hosta. Removing the spent flower spike by pruning back to the foliage from where it emerged will actually be a great help to the plant as you will be redirecting water and nutrients to other parts of the plants that will be eager to make use of it.

As far as the holes, I am 95% sure it is probably slug damage. The best way to tell is actually to go out and inspect your plant late-night with a flashlight, as that is when slugs are most actively chewing away. Don’t forget to look at the undersides of the leaves as well as their tops. I know there are some granular products out there that you can sprinkle on the ground that help wipe out slug populations, but once they are adults this late in the summer I am not sure how effective those products are. I am also not sure if the granular products are very organic as I do not have any of that around to check out the ingredients. To go about a more organic control, the best plan of attack for now is physical removal. Not to mention removing as much of the pests as you can means you do not have to alter your watering schedule too much. Good, deep watering helps freshly planted plants establish healthy roots quickly in your garden so I do not want to recommend cutting back on the water if you can help it. It is gross I know, but after a couple nights you will be able to get a lot of those slugs bagged up and removed from your garden. According to The Organic Gardener’s Handbook of Natural Insect and Disease Control edited by Barbara Ellis and Fern Marshall Bradley, thin copper wire laid around the base of your plants or copper used as garden edging works to deter them, though I have never tried it. You might think I’m crazy but some friends of mine even swear by pans of beer laid underneath the plants used as traps. Either way it comes back to physical removal being one of the best options to prevent future damage of your Hosta. I hope you can get the situation under control so that the slugs do not eventually spread to your new plants. Luckily the one thing about slugs is that they are not nearly as fast moving as some other pests in the garden.

Hale Damage and the Topic of Senescence

Question:
We recently had two hale storms on grand island. My hostas were ripped to shreds and I am in the process of cutting them back but was wondering if that might be harmful to next years growth. Not sure if they would be like daffodils and tulips and need the leaves to stay until they yellow. Your help will be greatly appreciated.

Answer:
Thanks for writing. Your assumption is right on target. In the world of horticulture there is a word that gets thrown around called “senescing” or “senescence”. When perennial herbaceous plants, like your hosta, begin to naturally yellow and die back in the fall we call that senescing. (Funny enough the verb “to senesce” can be difficult to find in some dictionaries, especially as it relates to horticulture and biology). And even though plants will senesce at different times of the year, the general premise holds true across the boards. Typically by that point the plant has achieved its fundamental biological goal of flowering or producing cones or producing spores in the hopes of reproducing and staying alive as a species. It has then maintained foliage to continue to photosynthesize and store nutrient and carbohydrate reserves for next year. By the time a plant yellows it has built up enough to leaf out and/or flower next spring and can thus go dormant for the rest of the off season. For this reason, most garden plants, from spring bulbs to late flowering herbaceous species, will be happiest and healthiest if allowed to keep their foliage until it naturally yellows and dies back.

As far as your dilemma I completely understand. Two years ago I was working at a public garden and a hale storm destroyed the majority of the large leaf plants in the woodland garden and we didn’t quite know what to do. I suppose what I would recommend is to leave what leaves you can. Even if the plants look a little lop-sided or sad, it will be best if they can utilize what leaf tissue is left to build up energy reserves before the fall. However, if they are really trashed then you have to do what you have to do, even though not ideal. You will sacrifice this years flower and the plants might get a slower or later start next year, but luckily hosta are some tough plants, so I can’t imagine you will actually lose any. Perhaps the plants will push out a new flush of growth this year, but I don’t want to get your hopes up in case that does not happen.

When to Divide Hosta?

(A beautiful inflorescence of hosta flowers found in Union Square, July, 2007. Photo credit: Alex Feleppa)

Question:

I wanted to divide a few of my hostas because they are too big. My hostas are beginning to bloom and I’m not sure if this is a good time to thin my plant. Should I wait until fall to divide my plants?

Answer:

You mean your hosta are beginning to leaf out, not flower, right? I don’t know of any hosta that bloom this early – the ones I see are just breaking ground with new leaves now.

Honestly, I think it would be fine to lift and divide them right now, but do not wait any longer. The general rule of thumb is that you want to lift and divide your large perennials and grasses soon after they flower so you give them enough time to establish new buds and flowers for next time. Often this means that spring flowering plants are divided in early fall and fall bloomers are best divided in early spring. Of course, there are always exceptions in the world of proper horticulture so if you are unsure it is best to refer to your favorite reference books before breaking ground. Hostas bloom late summer and are so tough, I have divided them in spring and fall and every time they have held up fine for me. Not to mention it is definitely easier to lift them, place them on their sides, divide, and transplant now while the foliage has not yet emerged, or is still very small. In some cases if I lifted and divided them on a sunny or hot day the foliage might have gotten a little beaten up, but again, they are such tough plants that I’m sure they would bounce back and be fine in the long run. If the foliage is up very far and you fear you might damage the plants too much to move them now then obviously you can wait until fall.