Thompson & Morgan Facebook Q&A Session 21st December - Your horticultural questions answered.

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Name: Yan Armour

Question: Hi everyone. Please can you tell me how to get rid of my ground covering ivy which I try to get rid for the past year without success. Thanks.

Answer: Hi Yan. Firstly, cut the stems back to 6" above ground level. Removing all of that top growth will weaken it and make it more manageable for you. If you are looking for an organic solution then your best bet is to dig out the roots with a fork, but I appreciate that this is an arduous task. You will need to keep an eye out for any regrowth which should be removed in the same way.

Otherwise, use a systemic glyphosate based herbicide such as Round Up which is best sprayed when the plants are actively growing in spring and summer. Choose an overcast, still day and take care to follow the manufacturer’s instructions to the letter. Obviously you will need to move any other plants that you wish to keep before spraying because glyphosate will kill these too. It may take a weeks or more for the chemical to have a visible effect on the ivy. If you notice new growth appearing a few weeks later then act quickly and spray it again. You will probably need to make several applications to eradicate it. Best of luck Yan.

Name: Lawrence Melia

Question: We have a california lilac which has got too big (6+ feet) tried to give it a haircut last year about this time and unfortunately a large chunk died (maybe from frost bite). How hard can I prune it?

Answer: Different types of California Lilac (Ceanothus) have different pruning requirements depending on their flowering period and whether they are deciduous or evergreen. I don’t know which variety you are growing but hopefully you can figure it out from the following information.

California Lilac flowering in late summer and autumn are best pruned in spring, whereas spring flowering varieties are best pruned in summer after flowering has finished. Evergreen plants require little pruning - you would normally just prune back the previous season’s growth by about half to maintain them within the allotted space. Unfortunately evergreen plants that have been neglected or outgrown their spaces are difficult to renovate as new growth will not always break from old wood. Therefore if your plant is evergreen then it is probably best replaced.

Deciduous plants should be pruned to form a good open framework in the first couple of years. Thereafter you can reduce the previous season’s growth by up to half each year. Deciduous specimens can often be renovated successfully by cutting back all of the stems to 30cm (12") above ground level. So if you have a deciduous plant then it is definitely worth a go in mid spring. I hope this helps you, Lawrence.

Name: Ian Woodhams

Question: Sue, I've got a 6" strip between a patio and West facing fence that's crying out for something to be planted. Any ideas for either ground cover or something to grow up the fence that will give all year round interest?

Answer: Hi Ian. There are lots of plants that will enjoy a sunny position like yours. Try these links for some ideas for covering west facing walls and fences or for some groundcover inspiration.

Name: Antonio Tarantini

Question: I have problems with germination of Ceratonia siliqua seeds: could give me some tips?!

Answer: Hi Antonio. Carob seeds will need scarifying before they will germinate - you can do this by rubbing them between two pieces of sandpaper until you can see the white endosperm showing through the tough seed coat. Once scarified, they can be soaked in water overnight or longer if necessary to imbibe water. Once the seed have swollen up in the water they can be sown in a very free draining compost mix. Best of luck Antonio.

Name: Janice Wellstead Brooks

Question: I’ve been given 6 Azaleas in pots. What is the best way to keep them overwinter. I intend to plant them in the garden eventually.

Answer: Hi Janice. Most azaleas are perfectly hardy so you can stand them outside for the winter and they should be fine. If they are very young plants then they may appreciate a sheltered position beside a wall or fence. When you finally plant them out, remember that they require an acid soil. If your soil is not acid then you may need to grow them in containers in the long term.

Name: Brian Dempsey

Question: I'd like to know how to get my Christmas Cacti to flower...... when they do flower it's only a few measly flowers, but other folks seem to get 100's of flowers. They both sit in an east-facing room but not in direct light. I'm not even sure how often to water / feed them. They seem quite happy to grow and produce new leaves but that's about it.....

Answer: Hello Brian. Schlumbergeras require a bright position and will normally produce more flowers if they are grown in brighter light (but not direct, hot sun as this may scorch them). I suspect that your plants might benefit from being moved - a west facing window might be preferable. Try to avoid positions next to radiators and draughts as dry air conditions can cause flower buds to drop.

Feed your Christmas cactus every 4 weeks while in active growth with a weak solution of high potash feed to encourage flowering. Water little and often to keep the compost consistently moist but don’t overwater by letting them stand in reservoirs of water. Once flowering has finished, reduce watering and keep the compost just moist.