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Q. Many leaves on the lower branches of my plants have gone yellow and have black spots; the others at the top of the bush are good and green.

ANSWER This is natural leaf fall and the plants will do this every year in the autumn.

Q. Why have some leaves on the lower parts of my rhododendrons gone silver on the top of their leaves?

ANSWER You have a Thrip problem that is easily cured with our Tree Health Bands. It may be necessary to prune back some other trees that have created too much shade, or are not allowing some breeze through your shrubbery.

Q. Why is my rhododendron not flowering?

ANSWER The main reason is usually lack of sunlight at the time plants need light to set flower buds on new growth i.e. November/December. Some bigger leafed varieties are slower to come into bud so be patient with these. Most varieties need good light for at least half the day and clear sky above is best. In hot climates, light shade or shadows passing over the plants in the hottest part of the day is ideal.

Q. Some of my plants in the older part of my garden have gone all leggy and don’t flower well now?

ANSWER Lack of sunlight is the main cause of this occurring. Prune back the overhanging trees to allow light into the top of your rhododendrons. You can then prune your plant back by 1/3 in late September to start with, if it responds well with new shoots the following season, you can do some follow up pruning to shape the plant. Alternatively delay pruning till immediately after flowering so you don’t lose the flowering.

Q. I have found this autumn that some leaves on my plants have gone brown at the ends of their leaves, especially the top leaves.

ANSWER This is the affect of the plants not getting enough water through the summer, next season with adequate water the new leaves will look normal. Tip; remember to mulch your garden and watch for leaves curling during the heat of the day, a sure sign some water is required. A good soaking once every 5 – 7 days is better than a little every day.

Q. I have had my plant in the garden for 2 years and it appears to be going more yellow in the leaves than when I bought it.

ANSWER Your plant is obviously not liking the position you planted it in. It could be a number of things, though most likely, heavy clay soil and correspondingly poor drainage. Please read the section on Soils.

Q. My garden soil is free draining and has good humus, but I have one or two plants in a large group that are looking poorly and not shooting like the others.

ANSWER You may have a pest problem such as grass grubs eating away at the root system. Dig down beside the root ball in the autumn to check for their presence. They will cause the plant to be loose in the ground and to have yellowish leaves and some varieties will have notches around their leaf margins. This damage is done by the flying beetles and is a sure sign that the grubs are present in the soil. It could also be best to dig up the affected plants and replant adding LAWNGUARD into the backfill along with compost and fertilizer.

Q. I would like to grow rhododendrons in containers, can you give me some hints on how best to grow these?

ANSWER Click here! for information on Growing in Containers.

Q. I have several deciduous azaleas with lichen growing on them. Is there a product that I can use to eradicate the lichen?

ANSWER Click here! for information on lichen and the product Surrender as a treatment.

Q. Sometimes I have rhododendrons that flower in the wrong season. What causes this and can I do anything about it?

ANSWER This happens in some seasons in the autumn when the weather tricks the plants into thinking it is springtime. There is no way of preventing this. Remember to break off the spent flower heads and then wait till the spring to enjoy the remaining flowers and hope the plants settle into a normal routine next season.

Q. Some top leaves of my plants have light patches on their upper surfaces?

ANSWER These spots are most probably a Powdery Mildew infection. The peak time for infection is Summer & Autumn. Starting a spray programme late spring with systemic & protectant sprays is the one option available. Allowing more breeze through your garden shrubbery will help keep it away or even shifting plants out into a more ventilated part of your garden would be better.

Q. I have several plants that have gone leggy, how do I go about pruning them?

ANSWER Click here! for information about pruning in our section on Plant Health.

Q. I have yellow flowering rhododendrons that seem more yellow in their leaves than others in the same bed, is this normal?

ANSWER We have always noted that the leaves on yellow and apricot flowering rhododendrons are inclined over time, in some soils to go slightly paler in their leaves. An application of a fertiliser high in nitrogen will usually change leaf colour in one season. Sheep pellets are also good and a mulch is always beneficial.

Q. Some of my plants curl their leaves during the day then next morning are looking OK, why is this happening?

ANSWER There are several reasons for this occurring. The most common cause is Water Stress. Rhododendrons and azaleas constantly lose water by transpiration through their leaves. Old established plants can survive periods of drought in the late summer because they are no longer in active growth. Leaves may wilt and curl during the day causing the plants to look stressed, but no damage results, so long as the leaves are turgid again by morning. If they are still curled or wilted in the morning action is needed e.g. a good soaking. Click here! for more tips on watering. Also branches of plants can be cracked or broken by pets or children. If you can definitely eliminate lack of water and broken branches for the wilting of the leaves, damage to the roots is a strong possibility. Click here! for more information on damage to the roots in our Plant Health section on Wilting Leaves.

Q. I garden in an area with a clay base quite close to the surface where I would like to plant rhododendrons and azaleas, what preparation do I need to do?

ANSWER  Click here! for information about Gypsum the Natural Soil Conditioner.

Please Contact Us for advice if you would like to discuss any problems, we will phone you at our earliest opportunity.

Opening times

365 Days

Nursery & Plant Centre

7 Days a week from Sunday 9th June 2024

Monday- Friday -10.30am - 5pm 

Saturdays 1pm - 5pm 

Sundays 10.30am - 5pm 

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Catering is available for pre-booked groups only, subject to availability, please contact our office to discuss.

Where to find us

339 Rangiwahia Road
RD 54
Kimbolton 4774
New Zealand

Contact us

P. 06 328 5797
E. office@crosshills.co.nz

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