Some are especially useful, bringing early summer colour to shaded spots in the garden.
They fall neatly into two groups; the biennials, mainly forms of our native purple and white foxgloves, which produce clumps of leaves in their first year which over-winter and flower in their second, and the perennials, which come in creams, orange-yellows and browns and, although perennial, tend to be short lived.
Our native foxglove, Digitalis purpurea, produces pink and white flowers in late spring and early summer.
It is usually found on the edge of woodlands, as it enjoys the light shade and the rich leaf litter.
This makes it useful for growing in similar lightly shaded spots in our gardens.
Plants grow to about 1.5m tall, so they can also be planted at the back of borders, mixed with deciduous shrubs which will provide a little shade for them.
The ‘Excelsior Group’ is a seed strain which has pink and purple flowers all round its flower spikes, giving it a fuller and more luxuriant look than the wild foxglove.
‘Sutton’s Apricot’ is another biennial, producing apricot-pink flowers.
The “rusty foxglove”, Digitalis ferruginea, is an exotic looking species from southern Europe.
It has particularly striking peachy-yellow flowers with reddish-brown veining on 1.2m tall spikes.
It also does best in shade or partial shade.
You can collect seed from the plants in your garden and sow them when they are ripe, usually in August.
Resulting plants will need carefully over-wintering, which can be tricky, so many prefer to carefully store seed over the winter and sow in the spring.
This is best done in a cold frame or greenhouse, using good quality seed compost.
It is essential that the seeds are left uncovered, as they need light to germinate.
Perennial foxgloves, left to themselves, usually live for about four years. Most can be propagated from seed.
Much easier is to divide plants every couple of years to rejuvenate them.
As many are natives of southern Europe, they generally prefer a sunny spot and soil that drains well over the winter.
Digitalis parviflora has unusually coloured brownish-purple flowers on stems about 90cm tall.
It is sometimes referred to as the ‘milk chocolate’ foxglove and needs full sun to thrive.
Digitalis grandiflora and D.lutea both bear cream-yellow flowers and grow 60cm tall.
Two new perennial foxgloves that are worth looking out for are ‘Lucas’ and ‘Martina’.
Lucas has purple-pink flowers on spikes about 70cm tall. It is also recommended as a cut flower and will grow in full sun or partial shade.
At 90cm, ‘Martina’ is taller and has pink flowers and silvery-green leaves.
Both produce flowers from June to September, even into October, depending on the mildness of the autumn weather.
This exceptionally long flowering season is partly due to their being sterile.
They don’t produce seeds, so concentrate their energies on flowering.
May is often the busiest month of the year as daylight length increases, temperatures rise and the danger of frosts subsides.
Harden off tender and half-hardy plants such as summer bedding, summer container plants and half hardy vegetables such as sweet corn and runner beans by gradually acclimating them to cooler, outdoor conditions.
They can be planted out when the danger of frost is past, usually towards the end of the month.
If a late frost is forecast cover them over night with horticultural fleece.
Water new plantings in dry weather and athorough soaking to the soil around the plant is better than a superficial spraying to leaves and the soil surface.
Watering in the evening will make best use of water.
On dry, sunny days keep annual weeds in check with a hoe.
Continue staking taller growing herbaceous perennials such as delphiniums.
Sow carrots, beetroot and salad leaves such as lettuce and rocket.
For best results, water the base of the seed drill first.