How to read a rose: types, stem length and the petals florists leave on

Three kinds of rose, grown for different jobs

Almost every rose in a florist's cold room belongs to one of three groups, and knowing which one you are looking at explains most of the differences in price, size and behaviour. They all belong to the genus Rosa, but they have been bred towards very different ends.

A standard rose carries one large head on a single straight stem. This is the classic florist's rose: bred for a tight, high-centred bud that opens slowly, a stem stiff enough to stand up in a tall vase, and petals thick enough to survive several days of cold, boxed transport. Most red roses sent for romantic occasions are standards, and when people ask for a dozen long-stemmed roses, this is what they mean.

A spray rose branches near the top of its stem into several smaller heads, usually at different stages from tight bud to fully open. Each head is modest, but one stem fills far more space than a standard, which makes sprays good value in hand-tied bouquets and invaluable in posies, buttonholes and low table arrangements where a large head would look clumsy. Because the buds open in turn, a spray stem changes over its life in the vase instead of peaking all at once.

Garden roses are the full, many-petalled, often scented kinds that look as though they were cut from a border. The ones florists buy are grown by specialist cut-flower farms from varieties bred to combine that old-fashioned cupped shape with a stem that will travel. The breeder David Austin, for instance, sells cut varieties such as 'Juliet' specifically for weddings and events. Garden roses cost more per stem, open faster and bruise more easily. Many also carry a scent that standard roses often lack, since breeding for vase life and transport rarely put fragrance first.

What a rose is actually graded on

Growers and wholesalers sort standard roses mainly by two visible measurements: the length of the stem and the size of the head. At Royal FloraHolland, the cooperative auction through which a large share of the world's cut flowers are traded, roses are offered against product specifications that record stem length and maturity stage alongside the variety, so a buyer on another continent knows what is in the box without opening it.

Stem length is sold in bands, and the band is much of what you are paying for. Head size is quoted less formally, but it tracks stem length closely, because a shoot vigorous enough to make a long, thick stem generally carries a larger bud on top of it. Uniformity matters too. A bunch in which every stem is the same length and every head is at the same stage is worth more to a florist than a mixed bunch, because it can go straight into a formal design without waste.

Maturity, or cut stage, is the third signal and the one most often misread. Roses bound for long journeys are cut while the bud is still tight, because a bud that is already loosening at harvest will be blown by the time it reaches a vase. A tight head on arrival is not a sign of a poor rose; it is a rose with its opening still ahead of it.

Why a longer stem costs more

The premium for length is not arbitrary. A rose plant produces its stems in repeated flushes, and each flush takes weeks to grow. If the grower lets a shoot grow on to a longer length, that shoot ties up the plant for longer, so fewer stems come off each bush over a year. A tall, thick stem also needs more leaf and more light behind it, which means more greenhouse space per plant.

Transport adds to the gap. Most roses sold internationally come from a handful of producing countries, including Colombia, Ecuador and Kenya, as well as the Netherlands, and a great many of them travel by air. Freight is charged on volume as well as weight, so a box of long stems holds fewer roses than a box of short ones, and each stem carries more of the cost.

Growing conditions set a ceiling as well. Farms on high ground near the equator get strong, even light all year and cool nights, which slow growth and tend to produce the thick stems and large heads that fetch top prices. Warmer, lower farms grow perfectly good roses, but they more often suit the medium and shorter lengths that go into mixed bouquets.

Whether the length is worth paying for depends on the vase. A long stem is essential in a tall, sparse arrangement where the stem is part of the look. In a rounded, hand-tied bouquet much of that length is trimmed away before the flowers ever reach water, so a shorter grade with a similar head gives the same effect for less. A good florist will tell you which you are buying and why.

The scruffy outer petals are there on purpose

People often receive roses, notice that the outermost two or three petals look darker, creased or slightly papery, and assume the flowers are old or were damaged in transit. Those are the guard petals, the tough outer layer that wraps the bud while it grows. They are usually marked because they have done their job: they took the knocks, the cold and the handling so that the petals inside did not.

Florists differ on what to do with them. Some strip the guard petals just before an arrangement goes out, for a cleaner look. Others leave them on deliberately, because a rose that still has its guards is better protected on the way to the recipient and through its first day in a warm room. Removing them makes the head look neater but slightly smaller, and it exposes the inner petals to bruising sooner.

If your roses arrive with marked outer petals, look at the layer underneath. If those petals are clean and firm, you can ease the guards away at the base once the flowers are settled in water. If the discolouration runs through to the inner layers, that is damage or age, not protection.

How to tell whether a rose is fresh

Freshness in a rose comes down to water and disease, and both leave signs you can check in a few seconds. The most useful test is a gentle squeeze of the head between finger and thumb, just below the petal tips. A fresh rose feels firm and gives only slightly. A head that feels spongy or hollow has already lost water, and it will open quickly and drop soon after.

• A firm head that gives only slightly when squeezed, with inner petals that are clean even if the guard petals are marked.
• A clean, pale-green cut end. Slime, a sour smell or brown mush at the base means bacteria have been growing and are already clogging the stem.
• Leaves that are green and springy, not yellowing, limp or falling.
• No small brown or grey spots on the petals. Those are usually grey mould, Botrytis cinerea, which starts in damp, cool packaging and spreads faster in a warm room.
• A neck that holds the head upright. A rose whose head flops just below the bloom has bent neck, which happens when water can no longer reach the top of the stem.

Bent neck is worth understanding because it is often reversible. The usual cause is air or a plug of bacteria in the water-conducting vessels, which starves the soft section under the head first. Recutting a few centimetres from the stem and standing the rose in fresh, clean water with flower food will often lift the head again within hours. A rose that droops a second time usually has a blockage too far up to fix.

When you are choosing roses as a gift, the practical upshot is short. Decide first whether you want one big head per stem or more flowers per stem. Pay for length only if the arrangement will show it. Judge freshness by the feel of the head and the state of the stem, not by the look of the outer petals. A tight bouquet of long red standards and a loose, scented bunch of garden roses are both good gifts; they are simply built from different roses for different effects.