Thompson & Morgan

Sue's Facebook Question and Answer Session 23rd July 2010

Name: Victoria Lewis
Question: I have noticed in a few of my pots the leaves are turning black at the tips and curling up a little. In one pot some Iris bulbs were doing very well but the leaves look like they have been singed and have funny creases at the ends too. what could this be??

Answer: As this problem is affecting quite a few different plants in your containers, this is likely to be a physiological problem brought about by something in the plants growing environment. Blackening of the leaf tips would suggest that the plants have dried out at some point. This is a common problem with plants that are grown in containers as they are almost entirely reliant on you for their water supply during dry weather. Try to establish a regular watering regime during summer when container grown plants are most vulnerable to drought.

Bright sunlight and strong winds can also affect the leaves, by scorching them. It is worth reviewing the plants that you are growing individually, and checking that they are placed in an appropriate position for their particular needs.

Physiological problems are also commonly brought about by sudden changes in the temperature. I suspect that this is the problem with your Iris. Iris leaves may become corrugated in response to drought and heat stress, or a sudden increase in temperature. My advice would be to cut back the affected growth and improve both their growing conditions and your cultivation practices. Hope that helps, Victoria.


Name: Andrew Goddard
Question: I have Horse Radish on my alloment, how can I get rid of it I have try some weed killer but it does not die (help Please)

Answer: Hi Andrew, I’m afraid you’ll need to be persistent with this! Dig up as much of the roots as you can (dig deeply rather than just pulling them up from the surface). This won’t completely eliminate the horse radish but the resulting new shoots that emerge may be easier to kill with a weed killer. Make sure you use a systemic weed killer that travels through the plant to the roots (such as Round-Up). With a combination of systemic weed killer and pulling up any new shoots you should eventually eradicate the horse radish (although it will take a few seasons).


Name: Karen Simpson
Question: Any ideas why my rhubarb is all spindly and floppy? I planted a crown last april, which my mother-in-law gave me, and I left it in the ground to settle without trying to harvest it for a year but it still doesn't look happy. It was growing perfectly well in her garden. What could be the problem?

Answer: Hi Karen, check your rhubarb isn’t too shaded from the sun as this may be causing the spindly growth; rhubarb flourishes in full sun and will grow poorly in the shade. Rhubarb also requires very high nitrogen levels in the soil so it’s advisable to apply a heavy dressing of manure or compost every autumn or spring. In addition give your rhubarb a feed in spring with a fertiliser high in nitrogenM. It’s also worth mentioning that rhubarb likes a free draining soil - waterlogged soil can encourage the crown to rot, so improve drainage if necessary. Hopefully you should get some nice big rhubarb stems to harvest next year.


Name: Judith Sullivan
Question: I have an orchid (Denobrium I think it is called), growing nicely 3years I have had it but it has started to grow what looks like roots up the stems, where there are off shoots, do I just leave it?

Answer: Hi Judith, without having a look at the plant, you may have either new plantlets forming on your Dendrobium orchid or new aerial roots growing. From your description it sounds like you could have new plantlets – referred to as “keikis”. They grow from the nodes of the orchid stem. There should be a small set of new leaves on a new off-shoot with roots forming at the bottom. If this is the case you can cut the new plants away from the parent plant with a sharp knife and either discard them or pot them up into orchid compost. Make sure the plantlets have a few leaves and good roots before removing them so they’re strong enough to survive on their own! Don’t water the new plants too much and mist the leaves until the roots have established – you’ll then have a stock of plants identical to the parent.

If they are simply new aerial roots then don’t remove them. If you’re still unsure please feel free to post a picture.


Name: Jackie Mason
Question: I have used compost that is peat free, and had dreadful results - my homegrown tomato plants and beans died, marigolds didn't grow etc. I had to buy last minute plants, put into grow bag compost mixed with home compost into big pots and they re now doing very well. Any ideas??

Answer: Hi Jackie. Peat free compost has long been a controversial subject among gardeners – you either swear by it or can’t stand the stuff! My own (very limited) trials suggested that the germination rates were reasonably even. However the plants grown in peat-free compost did not do as well as those grown in a traditional compost that contained peat. They began to show signs of nutrient deficiency quite early on and their growth became slower and less healthy.

Personally, I think that peat free composts have improved greatly in recent years, but there is still a massive difference between a good peat-free compost and a bad one. The trials undertaken by Which? Gardening seem to agree. I think it’s worth having another go though, Jackie, although I would suggest that you try a different brand this time. Perhaps we should ask our Facebook fans for their experiences with peat-free compost and find out their preferred brand?


Name: Kay Mckenna
Question: My 2 acers, different varieties, are both starting to revert to green.........help! I moved earlier this year and my garden is now north facing so am just wondering if they are in the wrong place

Answer: Hi Kay, have the existing leaves changed to green or are the green leaves appearing on new shoots? True reversion tends to occur for example on variegated shrubs, when the plant produces a new shoot with plain leaves (reverting back to it’s parent’s colour). In this case it is best to prune out the new growth to keep the variegation. If existing leaves have changed colour this may be the plants attempt to make use of the light, meaning the area it’s growing in may be too shaded to maintain it’s original colour. The plant will produce more chlorophyll (the green in leaves) to maintain energy for growth. The greening of the leaves is most likely due to the sudden change in growing conditions when you moved house. You could try moving them to a slightly brighter area (dappled shade is most preferred) and ensure they’re not exposed to cold winds. Mulch around the base of the plants this autumn to give them extra protection over winter. They probably just need a bit of time to settle into their new home!


Name: Di Shaw
Question: Why don't you make a container or containers that we can make a tower (smaller of course) for ourselves. I used pots but its not big enough. Look on my page and you'll see, successful but don't know what to use, ideas please.

Answer: We currently do not have a mini flower tower kit in our range, however, we regularly refresh our range, so keep checking the website!.