Perennials in clay soil

WildFlower_UK

Last spring we turned part of our garden into a place for wildflowers. We sowed using Beebombs, most of which have come up well again this year. There were some gaps as the Beebomb pellets form clumps rather than an even spread, and this year I've tried sowing some extra wild flower seed in one of the more sparce areas to see how it fairs. In other areas I've planted some perennials which I bought as plants from a garden centre over the weekend. Some were in flower (Erodium manescavii, Polemonium caeruleum blue, lupin gallery yellow) some yet to flower (Papaver yoyal wedding, Eryngium Miss Marble, Campanula medium blue). 



Our soil is heavy clay, and so where I planted the new perennials I made a decent sized hole and filled in with the clay soil mixed with about equal parts peat-free compost and some horticultural grit. I made sure the bottom of the hole had about 2inches of this loose soil mix too, to try and encourage the roots to grow out easier.

I guess my question is about watering with clay soil; should I water roughly once or twice a week with a good deep soaking, or daily but not as drenched? And is it worth me mulching around the base of the newly planted perennials? I'm keen to not mulch the whole area as some of the BeeBombs are annuals and/or self seeding. I already have landscaping bark I could use.

Nollie

I grow perennials in heavy clay, amended the whole beds with compost and grit and water deeply twice a week to encourage the roots to go deep and establish better. If you water lightly but more frequently, this encourages the roots to seek the water near the surface which is not so good. The only potential problem I can see is that you have created pockets of amended goodness and these can act as a water sump, so water deeply and less often to get the plants to send their roots down and establish better, but not so much that they drown in their little pockets. Hmm, I think that is called a ‘hedging your bets’ answer!

Also check the water requirements of each of the perennials you have chosen. For example, poppies and campanula grow wild in dry, cracked clay here, but it’s possible the cultivars you have may need a bit more cosseting.

They won’t need any additional nutrients in the newly amended soil, but a little mulch around the perennials with a low nutrient material might help conserve water in their first few months in the ground, but when everything fills out, each will shade the other and that shouldn't be necessary.

WildFlower_UK

Hi @Nollie. Thanks for such a quick and helpful response. Initially we planned to just grow with the Beebombs as they grow on anything, or at least there's a large mix that it was likely some of the flowers would thrive (which they did).

We took up turf and did our best to loosen the top 10 inches before we sowed last year, and are kicking ourselves at not adding some organic matter and grit at the same time (although we didn't want to make the earth richer as wild flowers prefer poor soil).

Sounds like I'm better to go for the water heavily but only once or twice a week option, with the hope the roots reach to deeper, moist soil. All of the perennial tags say to grow in full sun (which it largely is apart from towards the back where I have a foxglove and Campanula which are ok in part shade) and well-drained soil which I tried to create using the new soil mix. They also prefer a dry site, which I guess is another indicator that drying out in between waterings is preferable?

Maybe I'll add some mulch this summer while they are still establishing, but not worry after then which they've been in a while? Such a learning curve!

Butterfly66

Once established you shouldn’t need to water at all unless there is a prolonged drought.

WildFlower_UK

Thanks @Butterfly66! How do you check whether they're established? Is it usually a few weeks, months or a full year, etc?

BobTheGardener

I think you are doing the best you can and remember that one reason for putting down mulch is to suppress weed seeds, so it will also prevent many of your wild flowers from self-seeding.  I agree with @Nollie about the potential 'sump' effect and generally deeply watering rather than little and often, although you'll need to keep the seeds watered regularly for now until they germinate.

Hopefully your new seeds will germinate and fill the gaps.  Once the soil is covered, it will act as a self-mulch anyway and you can just weed-out any undesirables with may (will!) appear.

Lizzie27

I've found that polemonium in particular prefers a dampish soil and flops in hot sun so you may like to bear that in mind.

Butterfly66

If they are putting on new growth then they have established themselves - new leaves or flower buds appearing not existing leaves/flowers opening or getting larger. Any perennials planted last year and coming up again are definitely established and should be able to cope for themselves.

I only water perennials once on planting (a real soaking) and then during the first year I’ll give them some water if they appear to be struggling and/or we have a very prolonged dry spell.

WildFlower_UK

Cheers @BobTheGardener! I thought I had mentioned in a previous post about not wanting to mulch the entire 'meadow' area but see I left it out; I agree, I'd hate to prevent my wild flowers from self seeding.

Some of my recently sprinkled seeds have germinated already; is it now best to just water heavily at the same time as the rest of the more established area? Or keep giving them a daily moisture boost until they're bigger?

I'd like to fill in more gaps for next year; I just wanted to wait to see what grew this year before doing too much. When I do sprinkle more seeds in the Autumn, is it worth me doing anything to my clay soil other than just loosening the top few inches? I don't want to disturb the existing Beebombs and perennial roots too much.

WildFlower_UK

Thanks @Butterfly66, for explaining how to tell if they've established. I'll keep an eye to see if new buds or leaves are producing, and avoid watering as they got a good soaking on planting.

I wonder about my Beebomb wildflowers though; I've been watering them quite a lot since April (roughly every other day) especially as we've had a lot of sun where I am. Most seem to be OK although some clumps haven't grown much at all. Maybe I can tone this back a lot now they're mostly looking quite strong and green? They're usually a mixture or perennials and annuals.

Butterfly66

Yes I’d cut back on watering. You can always give them some if they look droopy. If they do wait until evening as some plants will recover once the temperature cools. 

I’m very economical with water as I‘ve always felt it’s wasteful to use mains water for the garden so I have to prioritise what gets water from my water butts 🙂 But it has shown me that a lot of watering is unnecessary and I’ve gardened on heavy clay and free - draining sandy soil. You just have to make sure you choose the right plants for your conditions and do what you can to improve the soil structure.