Gardening With Ken Podcast – May 2021

by Ken C | Last Updated: 25/05/2021

Every month, you can hear my Gardening With Ken Podcast on World Radio Gardening where I answer your questions on gardening – here’s the May 2021 edition.

This month I answer questions on Phlomis and flea beetles on Hollyhocks, advise on what can be planted in a tree stump, come up with a list of flowers and shrubs suitable for growing in heavy clay soils, and offer advice on pruning a Mulberry. Finally, I tackle the weather and cover off vegetables you can be planting in your garden now.

You can hear the episode on World Radio Garden by clicking here.


Announcer: You’re listening to World Radio Gardening.

Interviewer: It’s time to look through the bag of emails that we’ve got. They don’t come in the post these days do they Ken?  They come come electronically, the questions to World Radio Gardening.  And the inbox has been bulging this month hasn’t it?

Ken: It has indeed and in fact, it’s a sign of the weather and I suppose spring and leading into summer.

Interviewer: Yes, I wanted to come on to the weather. We’ll do that in a bit. But let’s dive straight in with the first question, which is from Jilly in Lincolnshire. She’s from Boston. Thanks for emailing Jilly.

Interviewer: Now, she has…

Ken: Phlomis.

Interviewer: Phlomis

Ken: I know it’s confusing because it’s a p-h on the front, isn’t it?

Interviewer: Yeah.

Ken: Plant names are very confusing. What’s up with her Phlomis anyway,

Interviewer: Well, during the winter, she says leaves are going brown and although the seed heads are attractive, when does she prune it?

Ken: It’s an interesting one funny enough Phlomis is still one of my favorite plants it flowers yellow during the summer period. Tell you what, there’s a lot in people think I’m talking about a car park plant because you know in the trade people think oh, it’s a car park plant. You know, some plants get accused of that. And in fact, there’s quite a few Phlomis at Hyde Hall in the car park but they’re still my favorite. They have a lovely yellow flower during the summer period stays on there quite a time. But they have this interesting sort of strange cone is it a flat cone head if that makes sense during the winter, and most people leave them on because they’re an attractive seed head. Erm, the going brown of the of the leaf, I think is due to the harsh weather we’ve had and also wind and cold will affect the leaves badly. They do sometimes go brown what I always do if you’ve got grotty leaves on a plant, I just take the leaves off. You can just pull them off with your hand if they’re feeling a bit rough. But she’s really asking is when do you prune? Well, you prune in spring so that all the damage has been done it tidy it up produces its new growth and then you’ll get your flower so there you are. I hope that helped.

Interviewer: Yeah, there you go Jilly, it certainly does.  And, off to Cheshire next. Lionel has got in touch on the email and we will give you the email address at the end so get your pen and paper at the ready. Lionel’s hollyhocks get rust and suffer with flea beetles. What can he do without using chemicals Ken?

Ken: Right, quite difficult the flea beetles are the first thing to deal with because thats usually get to the plant before you see them.  Erm, suddenly you’ve got all these sort of speckly little holes in there which makes the surface of the leaf very rough. They’re like pin shaped marks on the leaf, and that’s flea beetle. Now flea beetle you need to get to before you see it. So where there is a young hollyhock is growing, what I would do is put horticultural netting of fine fleece over it, not the horticultural fleece that we use necessarily for the cold although you could use that, there are nets that are specifically designed to not allow flea beetle through them.  And, if you peg that down over your hollyhocks that would work well.

Now when we come to the rust, not as easy. There’s really nothing much you can do hollyhocks get rust, they always have they most likely always will. And really rust is something that again, it’s another one where if the leaf is really unsightly, remove the leaf and that’s all you can do I’m afraid. But the organic method for the flea beetle I’ve just described, but can’t help with the old rust.

Interviewer: There you go Lionel, with the beetles of course, get in early before you see them.

Ken: Very early. Before you see them as the plant is growing.

Interviewer: The trick there. Thank you Ken for that.


Interviewer: We’re off to Maureen. Maureen now. Hello, Maureen. Thanks for sending us an email. She’s asking what’s a good evergreen Clematis and one that flowers in the summer? And also when does she prune it?

Ken: The trouble is the evergreen is generally flower in winter, so she might have to have to here two here do the job.

I would suggest that what she gets is the best evergreen Clematis in my opinion is still one called Clematis Cirrhosa. There’s several, there’s one called Freckles which has literally freckles little brownie stains in the petals. The petal is a drooping cluster type bell shaped flower very very attractive looks really nice and you’ll find it flowers just after Christmas.  Freckles has got the freckles there’s another one called Wisley Cream. Needless to say, it’s a creamy white color. These you want to have not too far from the house hope hopefully if so that you actually bother to look at them. They’re pretty tough, smallish leaf cluster of leaf, smallish leaf, evergreen, easy to grow. You just prune them after flowering in the Spring and off they go again you needn’t cut them down to ground, you can just face them up, and they work really well. If I was growing something like that, that’s delicate and soft I might go for something really blousy and showy in the in the summer. So, I might go for Jackmanii Superba. Now Jackmanii is known for its big, purple flower well Jackmanii Superba is a better grower, it’s an even bigger flower, and it will flower twice a year. You cut it down in February, and it flowers on its new growth, and sometimes you get a second flower a bit later on in the season. So have two. Don’t have one. I know they cost a bit of money, but quite honestly, you’ll get a better show that way.

Interviewer: Maureen, you’ve got to double up that’s what Ken’s saying.

Ken: Yeah, that’s it.


Interviewer: Ron is next out of the email bag. These are just a selection of the emails we’ve had, so thank you very much for all your emails and sorry if we don’t get to yours.  Ron’s on the Isle of Wight in Sandown.  And, he has a large treat tree stump, obviously as cut down a tree that’s now hollowed out. It’s about 18 inches high and he’s just wondering Ken whether there’s something he can plant into it to make it a bit of a feature in his garden.

Ken: For years, I’ve been telling people never keep tree stumps. Get rid of them.

Interviewer: Yeah.

Ken: Let’s just stay on that for a minute because you should get rid of a tree stumps because as they rot, they can spread fungal diseases through the ground into other trees. So please, anybody cutting down a tree, I know the tree surgeon will say, well, it’s another so many 100 pound to get rid of a stump if it’s a big one. Pay him get rid of it, it’s really worth it. Now. What we’re going to do for Ron Well, there’s not a lot that you can plant within a tree stump.  You could use, you could use a Wisely Cream you know, if you could hollow out enough. You’d need to dig it away so that you’ve at least got 18 inches across. Now what we don’t know, he says it is 18 inches high, but what we don’t know is how wide it is. If it was wide enough, you could fill it with compost you plant any climber is what I would do. Put a climber in and let it trail down over the 18 inches. You could easily use Ivy, but you know there are some ornamental Ivys there is some nice ivory looking Ivy’s and some crinkled ones with yellowish leaf as well. You could use Euonymus but quite honestly, I wonder whether I’d go for Clematis and then just let it hang over the side and that way you’re going to get flower as well. So that’s what I do. But preferably, I’d dig the blooming thing out.

Interviewer: I guess as well you mentioned, obviously, it’s gonna rot away? Yeah, it will be there for a little while if you don’t remove it, but but eventually it will. It will totally rot away and actually whatever you’ve planted there you know, it’s going to be lost, isn’t it?

Ken: Yes. Yes, it will indeed Owen.


Interviewer: OK, Reenie is next. Hello Reenie, thank you very much for sending the your email to World Radio Gardening, she is…. Do you remember the old nursery rhyme Ken about mulberry bushes?

Ken: Oh, yeah, yeah. Here We Go Round The Mulberry Bush, yeah.

Interviewer: That’s the one. We’re doing that with Reenie because she’s got a bush it’s about eight foot high. But she’s wondering how to make it from a bush into an actual proper tree.

Ken: Right. Okay. So if it’s a bush, I’m hoping it’s a normal Mulberry not a White Mulberry because you do need the Mulberry Morus Nigra I think it is or one of those. You need the red one. And all you do if a tree comes as a bush. The job is, and it’s what people do in nurseries, unless there’s two things they do in nurseries, they either take all the branches off slowly as a young tree and develop the trunk and allow the top three or four branches to actually develop into the tree or a tree is top grafted. In other words, they use a stem of a stronger type of tree and then they graft it. In this case she’s got something did you say it was eight foot high?

Interviewer: Eight foot, yeah.

Ken: So she must have three or four branches at the top that she could develop into the tree shape. And then, just take the side shoots off and you can take those off during the summer period it will bleed quite a lot, mulberries do bleed a lot, but don’t worry about that.  One way of stopping some of the bleeding on trees, like a mulberry in the summer, is you rub charcoal onto them.  That can sometimes help. But they will be bleed profusely but as long as you keep, keep it well watered and fed, it should be fine. And you might need to support it for a bit to develop that top crown of all branches.

Interviewer: There you go Reenie. There used to be where I used to work to large Mulberry trees just next to the offices, and every year once the mulberry berries, it’s sort of, you know, had their their prime, shall we say, and we’re beginning to ferment away and be passed they’re use by date. We used to find that the birds used to fly into the windows a lot more, because we think they were getting drunk on that fermented berries.

Ken: I could believe it, and I mean, it’s red, red and red. It’s. I know people pick mulberries, I know people who pick Mulberries I I think on World Radio Gardening we’ve we’ve actually been up to the farm at Wilkins where they’re picking them, and in fact it looks like you’ve got blood all over your hands because it is so they’re so rich red the berry isn’t it?

Interviewer: Certainly is yeah. Err, tasty if you have them when they are ripe but err, certainly. Reenie, there we go I hope that’s helped you.


Interviewer: We are off to London now Jerry has got in touch. He says he’s got really heavy clay where he lives Ken and need some advice as to what shrubs he can plant in in very heavy clay soil.

Ken: Right, well most shrubs will tolerate it but you do need to do a bit of preparation erm work. Avoid anything that likes acid soil that’s you avoid Rhododendrons, Azaleas, Camelias none of those like clay soil for a start, so avoid all those. Oh, and Pieris. Pieris is another one to avoid.  Daphne don’t grow so I’ve given you a list of don’t grow. Now what you can grow is you can grow shrub roses very successfully. Don’t forget that David Austin does a good range of shrub roses. They love a bit of clay. And you could grow Spirea again, Spirea comes as the white flowering one, you’ve got the Golden Princess with a pink flower and a gold foliage. Erm, there’s, there’s a wide range of those that will tolerate that sort of conditions. Viburnums, now Viburnums you’ve got evergreen ones, you’ve got Rhytidophyllum you got Viburnum Tinus and then you’ve got lots of different ones that you could be growing as well Opulus with its round, snowball type flowers. Viburnums a vast and you mustn’t forget that you’ve got winter flower and Viburnums as well. So, plenty of shrubs that you can plant.  Just a bit of advice though, when you’re digging out the hole, see that you’ve got organic matter buy a tree and shrub compost when you’re buying these plants, and then what I do is I put some of the compost round where I’m going to dig the hole and as I dig the hole, the soil that I’m digging out, even if it’s heavy clay, gets mixed in with the compost that I’ve left in a heap around where the holes going. And then you get a mixture of soil and compost, and that’s what you return around the plant after you’ve taken it out of the pot. And then, heel it well in and water it well in. ‘Heel it in’ means jumping on it with your, no not the plant, just where you planted where the soil around use your heel. And that’s what it means healing, healing it well in, push it well into the ground.

Got a Viburnum? Click here for my Viburnum pruning tips.


Interviewer: And I think it was on a previous podcast Ken about heat when you mentioned about heeling it in, and you do have to use the heel of your foot to really push it down. And we talked about watering well Ken, and actually it is a good time to come on to the weather we’ve experienced during April. Been extremely dry in parts of the country, there are some parts of East Anglia that haven’t seen a drop of rain at all, for the 30 days of April. And I saw on the television weather, them saying that actually during April we had 30-nights of frost. Now by my calculations, it means we had one every night.

Ken: I think that was yeah, ‘cause I think if you lived up north you got frost when it wasn’t in south and vice versa, I think isn’t it? I think that’s what happened.

 Interviewer: Yeah, pretty much. Yeah, yeah. So I mean, it’s a bit of a topsy turvy and it’s very unusual that we’ve had such a dry cold spell isn’t it this now late in the year.

Ken: I think it’s really difficult for gardeners and farmers can’t forget the farmers because they’re in a tough time as well. But, in gardens a lot of plants have been burnt by wind and frost. Now, the real trick we’ll cover that briefly because what you mustn’t do is you see it burnt and you think, “Oh, I’ll go out and cut all that dead off because it’s gone brown”. Don’t. Don’t cut it off.  Leave it alone. Wait until you’ve got your new growth, and hopefully you will get new growth from a lot of these plants, it might be lowered down, but it hopefully will come then you cut back to where the new buds are coming. As for dryness, well dryness is a major problem. Remember that you’ve just got to water the things that are the most important to you. And water those have been newly planted, and that’s going to be the trick. Because if you’ve got a plant in the ground, there is some moisture down deep, I’ve been digging and planting and there is some moisture in the ground. It’s not a great deal, but there is some there. So any plant that’s already established itself over the last year or so should be able to cope.  Watch for signs of drooping but generally water what you’ve planted this Winter and this Spring because lots of people have been buying plants and getting them in the ground as we know from what’s been going on at garden centers and retail nurseries.

Interviewer: Umm, yeah and actually I’m yet to put me tomato plants out the seedlings are going berserk under the glass.

Ken: Too cold. Don’t put your tomatoes out, no no.

Interviewer: Yeah, it’s too cold at the moment I darnt put them out.

Ken: Far too cold, yeah.

Interviewer: Having to wait just a little bit longer. Well finally Ken, the last email is from Jackie, she’s in the Cotswolds and talking about edibles. Err, she’s asking, when can she start to sow her carrots that she’d like to sow?

Ken: Well, in fact, it is a real problem. The soil temperatures are still far too low. Ideally, you’d remember Andrew Tokely from Kings Seeds down in Kelvedon, Horticultural Director he is, I always talking to him, his dad used to say it’s always it’s funny all these hand, hand me down hints from fathers and grandfathers. His father always used to say that you need seven degrees for seven nights right? Now that means you want to night temperature seven before the soil is actually warming up to sow most things. Er,. you’re not going to get that very easily at the moment. But it is still far too early for her to sow carrots. It really is. So hold on and just wait for warmer weather and it’s the nights you’re watching because I mean, let’s face it, you could be in your shirtsleeves in the day in the sun, but as soon as that sun goes in, the temperatures drop dramatically. And, that’s what you’ve got to watch out for.


Ken: I’ve had a chat with Andrew this week. Shall we do a few veggie ideas as well Owen?

Interviewer: That sounds like a plan. We can round off our podcast here on World Radio Gardening with those tips.

Ken: Okay, well Andrew, as I said is from Kings Seeds and Kelvedon and he went on and on at me about you know, that still the nights are too cold. Don’t rush to put any tender vegetables out. And this means that you’re getting you know, you’re getting them coming through the post. You’ve got your tomatoes are on the windowsill, aren’t they Owen? Waiting to go out/

Interviewer: They are, yes yup.

Ken: And you just can’t do it, you’ve got to hang on in. Erm, people are growing brassicas like cabbages and things like that lettuce, broad beans and you might have raised those or had them coming in to you, now you got to harden those off really.  Now hardening off means you’ve got to get them used to the outdoor temperatures. Now that’s not too difficult because what we do at the moment, if we haven’t got a cold greenhouse or a heated greenhouse, you take them out of the shed or green or even indoors, outside in the day. And then at night, as soon as you’re getting cold which is about 4:30, you bring them back in so you’re slowly getting them a climatized to the outdoor temperatures. And then things like broad beans you should be able to plant once you’ve climatized them, and same with some of the cabbages and even a winter flower, winter raised lettuce would tolerate some cold not necessarily frost when you’ve grown them indoors, but they will tolerate a bit of cold. 

Ken: New potatoes, lots of people put in their earlies and mid potatoes. Earth them up. Keep earthing them up as the leaves appear and if you’ve got to sign a frost, try and cover them over. Put a bit of horticultural fleece over now, to save the tops burning. Now what are you waiting for? Well, we talked about carrots when the soil warms up yes, get out there. Radish, beetroot, peas, spinach the it just goes on and on the list. And don’t forget, if you want to test the temperature, I mentioned this last time we talked about the tips from Andrew, sow a few radish they’re cheap. If they don’t come up within seven days, you’ve got a problem that the soil is far too cold. They should come up in about five days, if they are not up by seven it’s too cold. Keep trying with the cheap seed like radish. If you’ve got the opportunity of having a lean to greenhouse, or some way or perhaps a shed with some grant some glass in it that you can keep warmish, you cloud sow under glass now sweet corn, the courgettes, the marrows, the pumpkins and squashes, and even bring on runner beans and french beans ready for planting out at the end of May once all the frost has gone.  I think we’re going to be definitely waiting till the end of May before we can do anything.  And also at the end of May, I talked about those brassicas, the sprouting broccoli, winter Savoy’s and autumn cauliflower. Now you may laugh really Owen because believe it or not, you’re sprouting broccoli, you’re just finishing picking now. And there we are, we’re talking about sowing it now ready for next next winter and carrying it on into spring. So there are, it goes round and round in gardens doesn’t it?

Interviewer: Certainly does full circle.  And actually yeah, we need to be thinking now about the stuff for the late autumn and winter time. Yeah, I suppose it’s that time of year already, even though we were still having to hold on for the stuff that we expect to be planting out at the moment. Ken, thank you ever so much for going through all of the emails.

Interviewer: Again, apologies if we’ve not managed to get to your email on this podcast. Do keep sending them in. The email address to get in touch to ask your question is post@worldradiogardening.com that’s post@worldradiogardening.com, or you can give us a call. 033 33 44 00 14.  That’s 033 33 44 00 14.

Interviewer: Ken, our gardening expert here on World Radio Gardening, thank you ever so much for joining us.

Ken: Pleasure.

Ken Crowther is an award winning broadcaster, author and member of the Chartered Institute of Horticulture. He has been gardening for over 50 years and his knowledge and experience are drawn on to provide advice and information about garden design, plants for all seasons, gardening techniques and gardening tips. Gardening with Ken's broad appeal means he reaches a wide audience across the UK from amateur gardeners to top level horticulturists.