Dr Keith Hammett - Plant Breeder

11/12/2025

This form of green Clivia was originally bred in Japan by Toshio Koike and named after consummate plantsman Dr. Shuichi Hirao following his death. Although the name Hirao applies strictly to a single clone, the name tends to be used generically for this flower colour. New season seed now available. www.drkeithhammett.co.nz

05/06/2025

In a recent post, I reported on the success of Sweet Pea ‘Shell Pink’ at the world-famous Chelsea Flower Show, held recently in London.
‘Shell Pink’ is special in several ways. Unlike the majority of Sweet Pea cultivars, it is a hybrid containing genes from Lathyrus belinensis. It resulted from a cross made in 2015. ‘Enigma’ was the seed parent while ‘Future Shock’ was the pollen donor. Both are themselves L. odoratus x L.belinensis hybrids. Technically styled Lathyrus x hammettii.
When grown in full sunlight both the sepals and pedicels become chocolate coloured. This gives a unique tonality to the blooms.
www.drkeithhammett.co.nz

02/06/2025

It always gives me pleasure when I find one of the plants that I have bred, growing well in someone else’s garden. Imagine how I feel having seen images of Phil Johnson’s English Sweet Peas, Gold Medal winning display at this year’s Chelsea Flower Show in London.

Five of my cultivars were staged. ‘Shell Pink’ was centre stage and seed sold out. Phil said to reporters “We think this will be the next big thing”. ‘Shell Pink’ contains genes from Lathyrus belinensis and has distinctive dark brown sepals and pedicels.
A few packets are available on www.drkeithhammett.co.nz

Phil is himself an accomplished hybridizer and he launched the cultivar Amy Dowden at the show. Good that fellow New Zealand breeder Jack Hobbs was able to meet Phil.

Note especially the use of Sweet Pea foliage and tendrils in the vases. Tendrils are in themselves attractive and give a natural ambience more in keeping with current thinking regarding plants and gardens.

14/05/2025

Production of Sweet Pea seed in New Zealand had proven very difficult in recent seasons, as older established growers retired. As a consequence, I have been able to offer just a few of my cultivars. I only display cultivars that are available. No irritating “Sold Out” notices.

The season just past has been different. Lisa Lasenby in Marlborough was successful as has been John McCullough in New Plymouth. John has made a major commitment to the long-term production of Sweet Pea seed. So much so that he has formed the stand-alone company Egmont Sweet Peas Ltd.

Yvonne Baker of “Garden on the Hill” who works closely with me here, produces and sells seed on her own account. In addition to some of my cultivars she offers cultivars bred overseas.

Check out my website: www.drkeithhammett.co.nz to see around 70 cultivars now available

31/10/2024

When selling seed, it is important to be sure that a high proportion of that seed is viable. To this end I make regular small-scale sowings. Back in April, I sowed 10 seed each of 4 summer flowering Sweet Pea cultivars. All seed germinated and I did not have the heart to destroy nice vigorous young plants, so I potted them into 8 litre pots and grew them unheated under cover through the Northern New Zealand winter.

As anticipated, the plants did not start to flower until we had passed the Spring Equinox when day length hours started to exceed 12 hours per day. By 10 August the plants had reached 1m in height. By 4 October the plants were 3 m high, without flower buds, and it was not until 28 October that the first blooms opened, by which time thee plants were over 4 m high.

What do we conclude?

1. In warm climates Summer flowering types sown too early in the Autumn grow too tall before they are able to flower.

2. Similarly, if sown now Summer flowering types will not flower until they have been through a period of short days.

3. Sweet Peas can be grown successfully in relatively small pots, although a close eye on watering becomes very important as we move into summer.

Day length type of Sweet Pea is important. Spring and Winter flowering types can be sown now and into the New Year.

07/09/2024

Normally I say that soaking Sweet Pea seed before sowing is unnecessary. This year we have encountered a spread of germination times with the odd cultivar. When checked we have found that a few seeds had not swollen as their seed coats were hard and had prevented uptake of water. This was remedied by taking a chip off the seed coat away from the hilum (seed scar), after which the seeds quickly germinated.

Growers have come to expect all their seedlings to emerge at the same time. This has come about as a consequence of the Sweet Pea having been in cultivation for nearly four centuries.In contrast, for other Lathyrus species from the wild, such as Lathyrus belinensis, hard seed coats and staggered emergence is an evolutionary advantage. I always chip the seeds of L. belinensis before sowing.

Sweet Pea cultivars may demonstrate different shapes and sizes of seed, but there is nothing to suggest that any specific cultivars have inherently harder seed coats than others. It seems that in some seasons and under some growing regimes, hard seed coats may be produced.

At the other end of the spectrum, some cultivars do produce a proportion of seeds with split seed coats. Experiments have shown that these germinate well and certainly don't need chipping.

31/08/2024

When selling seed it is very important to check the viability i.e. germination rate and truness to description of each item.
The plants shown here were sown in April and demonstrated high viability, they are however summer flowering types and right now have reached 2 metres in height. They will not be able to start flowering until there are more than 12 hours of daylight each day, by which time they will be very tall.
People tend to sow Sweet Peas too early each year. Summer flowering types sown during September will flower by December. Winter and Spring flowering cultivars will flower by mid-November.

14/07/2024

Breeding plants is intergenerational. I often liken it to a relay race where participants pick up the baton, run their lap and hopefully pass on the baton. To encourage new breeders I have for some years offered segregating populations from both my Dahlia and Sweet Pea breeding programmes.

One of my goals has been to enhance the intensity of scent in the Sweet Pea and to explore the distinctive scents exhibited by different cultivars. I have lost my sense of smell, so I am reliant on the nose of wine expert Joshua Hall. Scent is complex and much harder to breed than colour. Equally, different people have different nasal ability. I have offered seed from the scent programme as 'Just Maybe' on the basis that one or more customers might just be lucky and detect a plant with exceptional scent.

This week a customer in Ireland contacted me to report on the performance of the seed he had bought and to ask about the pedigree of the seed. One of his plants has six of more flowers on each stem. A check on the pedigree revealed an Early Multiflora cultivar that I had used some three decades ago. Intense scent is reported.

Hint, now is Sweet Pea sowing time in the Southern Hemisphere.

06/02/2024