How to: split a large Stipa.

A question came in the other day, about how to split a large Stipa gigantea. 

In case you're not familiar with Prairie Planting - which is, to be honest, starting to lose its popularity now, but was dead trendy ten years ago - Stipa gigantea (common name: Spanish Oat Grass) is one of the backbones of this type of planting.

It's a big old thing, as you can tell from the name (gigantea, gigantic, yes?),  it is easy to grow, looks beautiful all summer long, and produces long, arching fronds in mid summer, from which the seeds - which do look a bit like oats, hence the common name - dangle elegantly.

Here's a view of one of "my" Prairie beds, from a few years back:

 This was taken in September, and it's a fairly typical Prairie bed: there are a lot of tall, large grasses, including some Stipa gigantea.

You can see that this is a bed of considerable size: most of those grasses in the back row are taller than my head height, and they really need beds of this size in order to reach their full potential.

So Stipa gigantea in a smaller garden can sometimes become a bit of a thug, getting too big for the space.

Especially when the flowering stems start to droop, as they can flop over paths, lawns, etc, and can become a bit of a nuisance.

As an example, here's a setting in which a pair of Stipa gigantea have grown too large for their positions: so large that they have killed off the grass over which they were spreading, to the point where I had to reinstate the edge with fresh grass - you can see, by the bare patch, how far over the grass the foliage spreads!

This photo was taken in the February of that year, when they were as near to "dying down" as they get, and you can see that even now, they are drooping over the grass.

So, getting on to the problem, what do you do with a Stipa that has outgrown the position, but when you want to keep it.

Answer: split it. This reduces it - in effect, you are "re-setting" it back a couple of years.

It's not an easy job, and the best time to do it is now, late winter, because it will be at its smallest, and because it is just about to start growing again.

Tools required: fork, second fork, back-up fork in case you break one of those two (joke!!), wheelbarrow and rake for the mess. Plus some other bits, which we will come to in due course.

First job: rake out all the dead stuff. This reduces the bulk, and allows you to see what you are doing.

How to do it: take your border fork, or ordinary garden digging fork, and rake them through - fairly carefully - like combing your hair:  hold the fork horizontally ie parallel to the ground, quite low: push the tines into the clump, going "underneath" the canopy, then lift the whole fork straight upwards, combing out the dead material. Repeat until your arms ache. Have a wheelbarrow beside you, for the combings, and rake up well afterwards.

 Next, cut them right back. Use secateurs, or even shears, and give them a good haircut, so they end up looking like this:

Yes, it is now a hedgehog.

One year, I did a "compare and contrast" experiment, where my Trainee cut first and then raked one of the two matching Stipa, while I raked first and then cut the other one, to see if either way was a) quicker, and/or b) better.

Our conclusion? 

Whichever way round we did it, I was much, much faster, but that was only to be expected.... *laughs*

Seriously, we found not much difference. So you can rake them through first if you wish, or you can give them a good haircut and then rake through what's left. On balance, I think my personal preference would be to cut first, because then you don't have such a length of foliage to rake through.

Either way, having reduced the foliage, you can now see what you are dealing with, so you can lift the clump.  Wrestle it onto its side, ram in the fork, and preferably another fork, or a spade, so you can do the "back-to-back" thing, to split the clump. This is where you push two forks (or a fork and a spade) into the centre of the clump (or into the side, if it's a huge one), back to back: then by pushing to two handles together, you lever apart the tines/blade, thus breaking the clump in half. 

This is hard work, but much better for the plant than getting a big knife and slicing it in half, because slicing it will, by definition, chop through the roots: whereas levering it apart means that both halves retain as much of their roots as possible. 

As with many herbaceous perennials, they tend to grow in a doughnut shape: the outer fringes will be the healthiest, and there may be a dead bit in the very centre, which should be discarded. 

This photo - right - shows this pattern, in a clump of Miscanthus (another Prairie Planting staple). You can clearly see the outer ring of actively growing stems, while there is a dead brown patch in the centre.

So having split the clump, you can break off this inner area of dead growth, as it is of no use.

If it's a really big clump, then splitting it in half won't be enough, so repeat the process until you get a number of good-sized clumps.

Plant the best-looking one back in place, having dug over the soil, and you might like to take the opportunity to add some fresh soil, or compost, or organic matter, because if the grass has been there for several years, it will have impoverished the soil.

The roots of most grasses are shallow, and they produce a lot of top growth, so some invisible support might be necessary: push some short garden canes right down into the ground, through the foliage, to hold it stable until the roots have re-established themselves. Water well, and within a few weeks it will start to sprout.

As for the other sections, don't waste them: either replant them elsewhere in the garden, or pot them up individually, water well, and put them somewhere sheltered, and keep watering them. This way, you will have several new plants which can be sold or given away, once they have re-rooted themselves.

So there you have it: how to split a large Stipa, or any similar large grass.

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