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Facebook Q&A Session 20th April 2012


Thompson & Morgan Facebook Q&A Session 20th April 2012 - Your horticultural questions answered.

Click here to view details of our previous Q&A sessions.

Name: Marian Donovan

Question: How on earth do you get the Streptocarpus seed to grow? I’ve had 2 packets of your seed and nothing happened. Did the instructions to the letter and nothing. Help.

Answer: As you will have discovered Marian, streptocarpus seed is extremely fine, so it is essential to take great care when opening the packets. I find that seed which are this small have a tendency to get stuck to the adhesive that seals the packet together! Open the packet over a piece of white paper in a clean, draught free area. When you rip off the top of the packet don’t throw it away until you have torn both sides of it apart and gently dislodged any dust like particles from the adhesive. Then open up the other three sides of the remaining packet and check for more dust like seeds. You can see just how tiny they are from this photograph.

Water the seed tray before sowing. Watering after sowing can dislodge the seed and wash them beneath the surface of the compost. You can gently brush the seed onto the surface of the compost, or moisten the tip of a toothpick and use it to lift each seed and set it down on the compost. Do not cover the seed with compost after sowing.

Cover the seed tray with glass or polythene to help maintain a constant humidity and temperature - ideally they should be placed in a propagator at a temperature of 20C. The seeds should take around two weeks to germinate. During this time it’s important not to let the surface of the compost dry out. Try to mist the surface it every day. Once they finally germinate, there is no hurry to uncover them until they are at least several mm high. Remember that they have been growing in a protected environment so you will need to remove the glass or polythene very gradually over several days, so that they become accustomed to normal room temperature and humidity. I must say that these seeds are very difficult to sow, so please don’t be disheartened or give up. Keep trying Marian - hopefully you will have success soon.

Name: Kaz Prescott

Question: Will "saponaria ocymoides" grow along my small crumbling wall outside? I need something to cover the wall as it’s a mess... does this stay green in winter? When is best time to plant this?

Answer: Hi Kaz. Saponaria is ideal for growing in rock crevices and once established will make a lovely display. Add a little soil into each planting crevice to help each plant establish and anchor it in place. Saponaria can be semi-evergreen in very mild areas but is generally deciduous. If you need a lot of plants to cover the wall then I would suggest that you grow them from seed . This will take longer but will be much more cost effective for you.

Name: Trixie Collin

Question: Can I get a poinsettia back to its former glory? It lost all leaves but now has new green ones.

Answer: This is a very common question Trixie - but you may not like my answer! My best advice would be to compost it and buy a new one next Christmas! Your Poinsettia would require a year of very precise care in order to rebloom next year. This would involve quite specific temperature controls, and an exacting regime of controlled daylight hours because Poinsettias are ‘short-day’ plants. This means that they will only start to flower 10 weeks after the day length shortens to 12 hours or less. To achieve this you would need to keep moving it to a completely darkened location from early October onwards for 12 hours each night. It’s all a bit of a fiddle and quite honestly, you can buy them so cheaply that it is best to leave it to the professionals!

Name: Kirsty Nunn

Question: My Magnolia Susan didn't flower this year and didn't/doesn't really have any buds on it all. It's in a pot and has been for 2 years and this is the first year with no flowers. Any ideas please? Should I re-pot it or plant in the ground? Thank you

Answer: That’s a shame Kirsty. If you had said that it had buds but these had failed to bloom then I would have suggested that they had been caught by the frost - a common magnolia problem. However, as no buds were produced then I think that this is an issue with its growing conditions, and a bit of extra care this year should rectify the problem. Firstly, I would suggest repotting the plant. If it is root bound then it will appreciate the extra space of a larger container. If it is not root bound then you can just repot it into the same container but use fresh compost - I would recommend John Innes No. 3.

This summer and autumn, try to make sure that the compost does not dry out by watering regularly. Drought conditions can cause a check in plant growth and prevent the formation of flower buds in the following spring. I would also recommend that you feed your magnolia this summer while it is in active growth with a general purpose fertiliser, or you can add a slow release fertiliser to the compost when you repot it. Hopefully these adjustments will help your magnolia bloom next year.

Name: Clare Rushton

Question: My wisteria has once again not flowered, 4th year running since we bought the house. It is a very well established wisteria. What should I do with it to encourage flowering next year?

Answer: Hi Clare. There are several reasons why wisterias can fail to flower. Immaturity is one reason, but I would normally expect to see flowers on a mature established plant. Summer drought is often a cause. Make sure that you keep your wisteria well watered from July to September as this is when the flower buds for the following spring begin to develop. I have a wisteria myself and I was astonished at how well it bloomed after I started to give it supplementary water during the summer months. I would also recommend occasional high potash feed which will encourage flower bud development too.

The other main cause of poor flowering or failure to flower is incorrect pruning. In winter you should cut back the sideshoots to within two or three buds from where they join the main branches. These will form flowering spurs that will bear the following year’s flowers. In summer, tie in the main branches to their supports. Two months after flowering, cut back the sideshoots to about 6 buds from the main branches. With proper pruning and extra water hopefully your wisteria should begin to flower.

Name: Jen Griffiths

Question 1: My clematis has not flowered for two years running and looks like no flower buds appear to be coming on the new seasons growth, it's growing up through my decking, which I had especially made around it as I couldn’t bear to lose the plant as it flowers are lovely, I cut it back every year early October. Please help

Answer: Hello Jen. Do you know what variety your Clematis is? This would help to determine what its pruning requirements are, as it is possible that you may be pruning your plant at the wrong time of year. There are 3 main pruning groups for Clematis depending on when they flower and whether they flower on new growth or the previous year’s growth. Take a look at this article for more information or let me know its name, if you can remember it.

I am also wondering whether you feed it. The plant appears to be putting on plenty of leafy growth and looks quite healthy. If you are feeding your clematis then I would recommend that you avoid fertilisers that are high in nitrogen and use a high potash fertiliser instead which should help to encourage flower initiation. Best of luck with it Jen.

Name: Jen Griffiths

Question 2: I have two peonies, brought from bulb in tesco four years ago, for only 1p each! Last year the flowered for the first time, this year have buds already, but hoping to move house this year and want to dig them up and take them. What are the chances of them making it?

Answer: It sounds as though they are doing well - what a bargain! You can certainly take your peonies with you - ideally wait until autumn to lift them when their foliage dies back. You can follow the planting tips on our How to plant peonies video when you replant them. If you need to move them before the autumn then try to lift as large a root ball as possible around each plant to minimise disruption to their roots. If you are unsure of where to re-plant them then you can always pop them into a container as a temporary home until you get organised in your new garden.

Unfortunately moving may mean that you will forfeit any flowers for the next few years while the plants settle into their new homes, but as peonies can live for up to 20 years, you should have plenty of time to enjoy them once they re-establish.

Name: Jen Griffiths

Question 3: Asparagus crown is in its third year of being planted. A week ago the first spear popped up. It is about an inch thick, looks lovely and healthy, but I was expecting more spears this year. It’s still early I know. But do I pick it? It looks very tasty.

Answer: Harvest it Jen - You have waited three years for this! Asparagus plants do take a few years to settle in but it should be fine to start harvesting your crop now. You can continue to harvest spears until the end of May. After May, stop harvesting your asparagus and leave the shoots to develop foliage. Late harvests risk weakening the plant and reduce your crop the following year.

Name: Carly Suzanne Luisa Smith

Question: My passion flower hasn’t flowered for three years, and the first year I had it I only got one flower. It’s not done anything this year yet. No greenery or anything. It is in a pot. Should I try repotting it?

Answer: Also my small olive tree in a pot lost all its leaves winter before last and has only grown a few back. It has retained them all winter. Hello Carly. It’s still very early in the year so you may not see much growth on it yet, but its well worth reviewing its growing conditions while your passion flower is still dormant. If the plant is root bound or has been in its container for a long time then it may benefit from repotting into a larger pot using a good compost such as John Innes No. 3. You can also try feeding it occasionally throughout the summer to try to encourage strong healthy growth, although passionflowers don’t require much feed. Use a high potash fertiliser, as too much nitrogen will make it grow foliage rather than initiate flowers. Finally you should review the position in which it is growing. Is it getting enough sun? If not then you may need to move it to a sunnier spot.

Regarding your Olive tree - try to be patient with it. Your Olive should replace its leaves in time but you not see any decent regrowth until summer. The main thing is to make sure that you keep it well watered and sheltered from cold winds. Olives are fairly drought resistant, but where they grown in containers they are always more susceptible to drought which will impair their growth. Once you start to see some growth on your olive it would be worth giving it a feed as well, to help it put on some strong growth.

Name: Gill Le Fevre

Question: Hi, when can/should I move daffodils? Also 2, I have a perennial wallflower that didn't flower much this year - what should I do to rescue it? And 3, if seeds are planted but the temperature is too cold, will they germinate when it warms up, or are they wasted?

Answer: Hi Gill - that’s a lot of questions! OK, firstly you should wait until the foliage has turned yellow and died back on your daffodils before moving them. This will help to feed the bulb for next year’s blooms.

With regard to your perennial wallflower - unfortunately Erysimum is considered to be a short lived perennial and is therefore often grown as a biennial and replaced after a couple of years. There is not much that you can do about this, although pruning after flowering and a good feed may help to prolong it for a little longer. What you can do however, is take some softwood cuttings this spring/ early summer which will replace your plants next year.

Finally, your seeds may germinate later on, but often you will find that they rot off during cold, wet weather. It really depends on what type of seed it is! Hope that helps, Gill.

Name: Anna Simon

Question: Hi, my asparagus has started to come through and many of the spears are curled over and look withered. What could I have done wrong? Thanks.

Answer: Hi Anna. The main pest of asparagus is the Asparagus Beetle which emerges in spring to lay its eggs on the spears. The larvae feed on the tips of the spears which causes similar damage to what you describe. However it is still quite early for Asparagus Beetle damage. The most obvious cause that springs to mind is a lack of water. Asparagus needs consistent moisture levels and unfortunately we have not had much rainfall this spring. Also, the soil may be a bit compacted, in which case the spears will often push through the soil slightly curled over and then straighten up afterwards. A little light cultivation of the soil surface and some decent rainfall should rectify this problem, but I would also try to keep it well watered throughout the summer to prevent the soil drying out.

Name: Lindsey Cooper

Question: What is the difference between a cold frame and an unheated greenhouse??

Answer: Hi Lindsey. There is not much difference except for the size. An unheated greenhouse has a larger volume of air in it so it may be a degree warmer but really there is little difference.

Name: Sara Le Page

Question: I had lots of lovely daffodils this year but they are now dead...when can I cut the foliage down, I'm desperate to plant some more stuff!

Answer: Hi Sarah. You need to wait until the foliage has turned yellow and died back before you cut them down. The reason for this is to feed the bulb for the following year. If you cut them back too early then they may not flower as well next year. Try to remain patient for the time being.

Name: Steve Linden Wyatt

Question: Last I grew lupins from seed and they did really well. They established as a plant and flowered. However some were eaten by something but I could not see what it was. Do you know what it could be? I have noticed some new shots on one of the eaten ones but the ones that were not eaten remained as a plant through the winter.

Answer: Slugs and snail love young lupins, and I would guess that they are the most likely culprits. Try scattering some slug pellets around them and then take a look a few days later. You will probably be quite surprised at just how many of them were trying to eat your plants!

Name: Lesley Gilbert

Question: Hi Sue, My friend would like to train a peach tree (espalier) on his south facing house wall. He thinks he may have approx 2-3ft of top soil before reaching a hardcore base. Is this enough to give it half a chance or would he need to dig further? Is there anything else he needs to consider? Thanks

Answer: Hi Lesley. Tree roots tend to grow fairly shallow and wide, so a depth of 3ft should be just enough soil for your friends espalier to grow successfully. However, he can make the soil deeper by building an open-bottomed raised bed in which to plant the tree if the soil is not as deep as he had hoped for. The tree can then root through this bed into the soil beneath if it needs to. The key to fruit tree establishment is regular watering throughout the first year after planting to help it establish successfully. For more tips on growing peaches click here and take a look at the ‘How to grow’ and ‘Aftercare’ tabs.