Gadenin日本語Get the appWhen the flowers come and how long they hold
From germination to the first open flower is roughly eight to ten weeks in cool weather. An autumn sown plant that has overwintered as a rosette moves much faster in spring, because the root is already made, and it can be in flower within four or five weeks of starting into growth. Once open, a healthy patch flowers continuously for six to ten weeks, ending abruptly when the first sustained heat arrives rather than tailing off gradually.
Each individual flower is an open bowl about an inch (2.5 cm) across and lasts two or three days before the petals drop cleanly away. The plant carries dozens of buds at once at the tips of every branching stem, so the display is made of constant replacement rather than long lasting individual blooms. Flowers close in dull weather and at night and reopen in the morning, which is normal and not a sign of anything wrong.
| Stage | How long | What you should see |
|---|---|---|
| Sowing to emergence | Seven to fourteen days in cool soil | Even scatter of small paired seed leaves |
| Emergence to branching | Three to four weeks | Ferny divided leaves, plant still low and flat |
| Branching to first bud | Two to three weeks | Stems lengthening and sprawling outward |
| First flower to full sheet | Ten to fourteen days | Whole patch covered, individual plants no longer visible |
| Full flower to collapse | Six to ten weeks | Ends when day temperatures settle above 80F (27C) |
Why a patch does not flower
Overfeeding is the first cause. Nitrogen from manure, compost dug in fresh, or a general purpose fertilizer sends the plant into leaf, and a nemophila in soft growth simply does not set buds until the flush is over, by which time it may be too warm to flower at all. The cure is prevention: sow into unimproved soil and feed nothing until buds appear.
Shade is the second. Under two or three hours of direct sun a day the plant survives, stretches and produces a thin scatter of flowers on long stems. It wants full sun in a cool spring, and only needs afternoon shade where spring is hot. The third cause is sowing too late, which is really a heat problem in disguise: the plant reaches flowering size just as the weather turns against it, opens a handful of flowers and gives up. Very dry soil during bud formation does the same thing on a smaller scale, causing buds to abort before they open.
Stretching the season out
There is no useful deadheading with nemophila. The flowers are small, they self clean, and there are far too many of them to pick over. What does work is a light shear over the whole patch when the first flush starts to thin, taking off the top third of the growth with shears. If the weather is still cool, the plant breaks from lower down and gives a second, shorter flush within two to three weeks. If it is already hot, the shear will not save it and you may as well leave the plants to set seed.
Successional sowing is the other lever, and it is a limited one. Two sowings three weeks apart in early spring will extend the display by a fortnight or so, but a third sowing is usually a waste of seed because it runs into summer regardless. In climates with mild winters, the real extension comes from sowing in autumn instead: those plants start flowering weeks before a spring sown patch and are still going when it begins.
- Watch for the flush to thin When you can see stems and leaves through the flowers again, the first flush is ending. That is the moment to decide between shearing and letting the plants seed.
- Shear only in cool weather Take off the top third with shears, water once afterwards, and give it a fortnight. In warm weather this just kills the patch faster.
- Leave a section unsheared Keep a strip at the back or the end of the patch uncut so it can ripen seed for next year while the rest reflowers.
- Stop watering when it turns hot Once the plants start yellowing in heat, extra water only rots the crowns. Let them dry down and finish.
Color, and what changes it
The flowers are a clear sky blue with a pale, almost white center, and the intensity of that blue varies with temperature and light more than with anything you do at the roots. Cool nights and strong daylight give the deepest color; warm, dull weather washes it out toward pale lavender. Plants in a shaded position are usually paler as well as sparser, which is another argument for the sunniest cool position you have.
Color also fades as an individual flower ages, so the pale flowers in a patch are simply the ones about to drop. A whole patch turning pale at once, on the other hand, usually means a warm spell has arrived and the season is nearly over. Note the date when the color changes, because it is a reliable early warning that gives you a week or two to collect seed before the plants are finished.
What to record about flowering
Log the date of the first open flower and the date the patch peaked, alongside the sowing date. The interval between sowing and first flower is remarkably consistent in a given garden, so after one season you can count backwards from the date you want flowers and sow accordingly. Record the position of the patch as well, because the same interval shifts by two weeks between a warm south facing bed and a cool one.
It is also worth noting whether you sheared, when, and whether a second flush actually came. Shearing pays off in some climates and never in others, and the only way to know which one you garden in is two years of notes.