Polemonium caeruleum

For herb plants, please see our Looking Good List for availability. You can organise a Farm Collection, collect at one of our Open Days or during a Herb Experience. Please use our online webform or email your list directly to us (sales@jekkas.com).

We no longer offer a general mail order service for our herb plants but we do offer a limited selection of Jekka's Culinary Herb Boxes.

The Botanical Name is known throughout the world. It includes the genus and the species plus in some cases the cultivar. For example Agastache is the genus, rugosa is the species and Agastache rugosa ‘Golden Jubilee’ includes the cultivar.

The Common Name is the name by which the herb is commonly known, for example thyme, sage etc. But please be aware that common names are often colloquial and relevant to the area in which you find them.

The Plant family is the group of plants which is more comprehensive than the genus.

Want to know more? Read Jekka's Blog containing tips for understanding herbs.

- Annual a plant that lives for just one season (see Jekka's Annual Herbs).
- Biennial a plant that produces leaves in the first season and flowers in the second, then dies (See Jekka's Biennal Herbs).
- Climber/Vine a plant that cannot grow without the support of other plants or structures.
- Deciduous a plant that drops it leaves in winter.
- Evergreen a plant that has leaves all winter (See Jekka's Evergreen Herbs).
- Herbaceous a plant that dies back into the ground in winter, becoming dormant, before reappearing in the spring.
- Monocarpic a plant that dies once it flowers; it can live for a number of years before flowering.
- Perennial a plant that lives for a number of seasons, most flower annually once established (See Jekka's Perennial Herbs).
- Partial Evergreen a plant that holds some leaves throughout the winter.
- Shrub a woody stemmed plant that usually freely branches from the base.
- Sub-shrub a small, short, woody shrub, especially one that is woody only at the base.
- Sub-tropical a plant that can only survive in a warm, damp climate that does not drop below 10°C at night.
- Tree a woody plant that usually has a single stem.
- Tropical a plant that can only survive in a warm, damp climate that does not drop below 15°C at night.

Recommended planting position in the garden or where to place a pot, e.g. sun, partial shade etc.

Plants grow in many shapes and forms:

- Upright: a plant that is very straight.
- Clump: a plant that grows in a neat compact shape.
- Bulb: a plant that dies back into a bulb.
- Mat forming: a plant that grows low to the ground and makes a neat mat.
- Creeping: a plant that grows along the ground and produces roots at intervals.
- Bushy: a plant that, in the main, tends to be a shrub which makes a bush-like shape.
- Arching: a plant that grows upright then the growth arches, ideal for growing over a wall or in a container.
- Prostrate: a plant that lies flat on the ground.

This indicates the average spread and height that the plant will achieve in its life. It helps to know this when positioning plants in the garden. Bear in mind, that height and spread vary in definition according to the following plant types:

- Annual: this is the spread to which it will grow, and the height when in flower during the year.
- Biennial: this is the spread in the first year and the height of the flower in the second year.
- Herbaceous perennial and perennial: this is the spread the plant will achieve after a number of years once mature and the height when in flower.
- Shrub/evergreen tree: this is the average spread and final height after a number of years of growth.

All ratings refer to UK growing conditions and are based on the Royal Horticultural Society hardiness rating. The minimum temperature range, in degrees centigrade, are shown in the brackets below:

- H1a (15°C minimum): Under glass all year.
- H1b (10°C to 15°C): Can be grown outside in summer.
- H1c (5°C to 10°C): Can be grown outside in summer.
- H2 (1°C to 5°C): Tolerant of low temperatures but will not survive being frozen.
- H3 (-5°C to 1°C): Hardy in coastal and relatively mild, sheltered parts of the UK.
- H4 (-10°C to -5°C): Hardy through most of the UK.
- H5 (-15°C to -10°C): Hardy in most places throughout the UK, even in severe winters.
- H6 (-20°C to -15°C): Hardy in all of the UK and northern Europe.
- H7 (-20°C and below): Hardy in the severest European continental climates.

The soil is the engine of your garden, so it is important to know its condition before you start planting. Good plant growth is not only dependent on how much you feed the soil but it is also dependent on the structure of the soil. Soil can vary from acidic (pH 3.5) Sphagnum moss peat to alkaline (pH 8.5) Fine loam. Most herbs will tolerate a range of between 6.5 and 7.5 pH which is fairly neutral. There are always exceptions, for instance Rumex scutatus, Sorrel, will tolerate acid soils.

The pH of the soil refers to its acidity or alkalinity. It is a vital factor in the plant’s ability to obtain, via its root system, all types of plant foods and essential chemicals. For example, an alkaline soil can produce stunted plants with yellowing leaves. This is because the minerals, especially iron, have become locked up in the soil. At a neutral pH of 7, most of the essential chemicals and plant foods become available to the plant so producing healthy plants.

The following 4 basic soil types are the most suitable for growing herbs:

- Clay 6.5 pH: This soil is composed of tiny particles that, when wet, stick together making the soil heavy and difficult for the roots to penetrate and in summer, when dry, sets rock hard. Even though it can be rich in plant nutrients, because of its characteristics it is improved by working in extra well rotted leaf mould or compost. This will improve the structure and allow young plants to become more easily established.
- Chalk 8.5 pH: This soil is light with lumps of flint or chalk, well drained and often shallow. It has a high pH making it very alkaline. It is possible to increase the nutrient content by adding loads of compost but it is difficult to lower the pH. A large number of herbs will tolerate chalk. However, considering the characteristics of this soil, to give it depth and help it retain moisture it may be easier to grow the herbs in a raised bed.
- Loam 5.5–8.5 pH: This is often considered the ultimate garden soil in which most herbs will grow. There are various types of loam depending on the content of clay or sand. A sandy loam is the best soil for growing the largest range of herbs as it is rarely waterlogged in winter, is dry in summer and it is naturally high in nutrients.
- Sand 4.5 pH: This soil feels rough and gritty when handled. It is very free draining, which means that the plant’s nutrients are quickly washed away. A plus point to this soil is that it is quick to warm up in the spring so sowing and planting can be started earlier than in clay soils. To help it retain moisture it needs to be fed in winter with leaf mould to retain moisture and with well-rotted manure for an extra source of nutrients.

Checking the pH of the soil
To test your soil buy a soil testing kit from any good garden centre or store. The majority of amateur soil testing kits are very simple and rely on colour rather than a numerical scale. Acid soils turn a solution yellow- orange, neutral turn it green and alkaline turn a dark green.

Want to know more? Read Jekka's guide to soil.