Origanum (oregano and marjoram) trial results 2022–2023
Objectives and purpose of the trial
Oregano and marjoram plants in the ground and pots at RHS Wisley
Forum judging the Origanum trial in June 2023
What is an RHS Award of Garden Merit?
The RHS Award of Garden Merit (AGM) is intended to help gardeners choose plants that are likely to perform well, and is only awarded to plants that are:
- Excellent for ordinary use in appropriate conditions
- Available
- Good constitution
- Essentially stable in form and colour
- Reasonably resistant to pests and diseases
Judging criteria
The following factors were all taken into consideration as part of the judging of the trial:
- Foliage quality
- Flower quality
- Habit and overall impact
- Vigour and persistence
- Pest and disease resistance
- Culinary potential
- Hardiness
Origanum (oregano and marjoram) AGM winners
Origanum rotundifolium 'Jan's Pink'
round-leaved oregano 'Jan's Pink'
- 0.1–0.5 metres
- 0.1–0.5 metres
Origanum vulgare 'Pink Mist'
oregano 'Pink Mist'
- 0.5–1 metres
- 0.5–1 metres
Origanum rotundifolium 'Jan's Pink'
round-leaved oregano 'Jan's Pink'
- 0.1–0.5 metres
- 0.1–0.5 metres
Origanum vulgare 'Pink Mist'
oregano 'Pink Mist'
- 0.5–1 metres
- 0.5–1 metres
In the past, herbs such as oregano were tested for their appearance rather than culinary value. This time the trial forum members were flavour testing as well.
Why the AGM was awarded
Terracotta pots planted with trial entries in July 2023
View of the trial beds planted with oregano and majoram plants
AGMs rescinded
Plants and location
What was planted?
Where was it planted?
The trial took place in the Trials Garden at RHS Wisley, Surrey. The plants were supplied to the RHS as 9cm pots, and each variety was planted in both the ground as well as in terracotta pots (37cm diameter) in July 2022. Here are some considerations for planting out Origanum (oregano and marjoram):
- Plant in sunny, free-draining growing conditions, in the ground or in containers
- Once established plants shouldn’t need additional watering when growing in the ground. In containers, the compost will dry out rapidly, so water regularly over the summer months
- You can harvest the leaves regularly through spring and summer. Pinch out new leaves to encourage bushy growth for a plentiful harvest
- In late spring or early summer, after the last frost, clip back established oregano plants to keep them compact and remove any shoots damaged over winter. This will encourage a flush of new growth
- These closely related herbs share similar leaves and clusters of lipped flowers, but oregano’s stronger, spicier flavour and winter hardiness sets it apart. Both are great for pollinators
Cultivation
Planting process
Open ground plants
Four plants of each trial entry were planted in squares with 45cm between plants and 65cm between entries. They were grouped together as green, variegated and gold leaf plants. Barley quartzite gravel was placed on top of the entries with biodegradable mulchmat underneath to prevent weed growth.
Container grown plants
Three plants of each trial entry were planted in terracotta pots (37cm diameter) using triangle formations and multi-purpose compost. Slow release fertiliser was applied at planting. During the winter months, the pots were protected under cover in a propagation area to keep the plants frost-free.
How plant health was managed
Maintenance
Over the course of the trial, the front left plant of each entry was cut back by two thirds after flowering. All other plants were left unpruned. The RHS Trials Horticulturists noticed that the unpruned plants grew back faster each spring. This could be because the dead stems and old leaf litter left behind created a microclimate. This difference evened out later in the growing season.
Watering
The plants growing in the ground were only watered during really dry spells. The container plants were watered regularly during the summer as they dried out quicker.
Weather
The hottest day ever recorded at RHS Wisley was in summer 2022 when the temperature reached 38.6°C. December 2022 was the coldest start to a meteorological winter since 2010. The temperature dropped suddenly to -8.1°C following a mild autumn, causing frost damage. Clear skies overnight led to intense radiation frost, which caused most of the damage across RHS Wisley. In this trial, a number of plants were lost.
Challenges
The oregano and marjoram plants were generally pest and disease free. Powdery mildew and leafhoppers were present and towards the end of the season leaf spots became more of an aesthetic problem.
How to grow oregano
Explore all the information you need to know to grow and care for oregano in your garden
Discoveries
June 2023
The trial was situated in a part of the Trials Garden with some shade cover during the day from a nearby oak tree. The RHS Trials Curatorial team noticed that the yellow-leaved selections suffered less bleaching here than in the containers that were in full sun. Plant performance was not adversely affected by the shade cover.
Who was involved?
Judges of the trial
The Origanum (oregano and marjoram) judges included: Paul Turner (Chair, Garth Cottage Herbs), Janice Shipp (Vice Chair, garden writer), Tom Brown (West Dean Gardens), Virginia Colquhoun-Gonzalez (Horticultural Trade Manager), Diane Clement (Alpine Garden Society judge and speaker, RHS Alpine and Rock Garden Committee member), Alison Dodd (Herbs Unlimited), Holly Geipel (Horticultural Trade Manager), Ian Hodgson (garden writer, Garden News), Jekka McVicar (Jekka’s Herb Farm), Sigrid Sharp (RHS Edibles Horticulturist).
Suppliers to the trial
- Barnes Nurseries
- Binsted Nursery LLP
- Claire Austin
- Garth Cottage Herbs
- Hetty’s Herbs & Plants
- Ice Alpines
- Kirton Farm Nurseries Ltd (The Hairy Pot Plant Company)
- Malcolm Allison Plants
List of plants in the trial
Handy tools and information
- Full article - Filter for AGM plants and refine by colour, height and season of interest
Find an AGM plant online
Filter for AGM plants and refine by colour, height and season of interest - Full article - Explore advice and helpful tips from our resident experts
Gardening advice
Explore advice and helpful tips from our resident experts - Full article - Check how hardy plants are using the RHS hardiness ratings system
Hardiness ratings
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Get in touch
For more information on our RHS Plant Trials or to access older trial reports, please get in touch with our team via email at [email protected].
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