Gadenin日本語Get the appLate winter to early spring: waking the rhizomes
The year begins in storage. Towards the end of winter, check the crates and look for growing points that are swelling and turning pink. That is the plant telling you its dormancy is ending. Discard anything soft or rotted at this point rather than planting it in hope, and decide which clumps are big enough to divide.
Divide by cutting the clump into pieces each carrying three to five growing points and a good body of rhizome. Throw away the old woody core from the middle of a large clump, which has few live points and stores badly. Let the cut surfaces dry for a day in a frost free place before they go into soil.
Where spring is long and cool, pot the divisions into 1 gallon (4 liter) containers at this point and hold them at 65 to 70F (18 to 21C) with light watering. Six weeks of this brings plants into flower two to three weeks earlier than rhizomes planted straight into the ground, which matters a great deal in a short season.
Spring: planting into warm soil
Do not plant on a date. Measure the soil at planting depth and wait for 60F (15C), with the last frost past. Before planting, work 2 to 3 in (5 to 8 cm) of compost into the top 12 in (30 cm) of the bed with a balanced slow release feed, because canna is a heavy feeder and the first six weeks of growth set the size of the plant.
Lay rhizomes flat, growing points up, 3 to 4 in (8 to 10 cm) deep, spacing tall types 18 to 24 in (45 to 60 cm) apart and dwarf types 12 to 15 in (30 to 38 cm). Mark each position with a cane. If a tall type is going in singly in an exposed place, drive its stake in now, while you can still see exactly where the rhizome lies.
Give no water until the first shoot breaks the surface. In warm soil that takes two to three weeks. Once shoots are up, begin normal watering and start feeding when the plants reach 12 in (30 cm).
| Stage | Main job | What to check |
|---|---|---|
| Late winter | Inspect store, divide clumps, pot up under cover | Growing points swelling, rot or shrivel in the crates |
| Spring, soil at 60F (15C) | Plant rhizomes 3 to 4 in (8 to 10 cm) deep, stake tall types | Soil temperature at depth, last frost past |
| Two to three weeks after planting | First watering as shoots appear | Every marked position has produced a shoot |
| Early summer | Feed every 2 to 3 weeks, mulch 2 in (5 cm), water deeply | Tight new spears for leaf roller silk and frass |
| Midsummer to first frost | Cut each finished cane to the base weekly | New spears appearing at the crown after each cut |
| Six weeks before first frost | Stop feeding, reduce watering | Rust on lower leaves, bud rot in wet spells |
| After the first blackening frost | Cut canes to a 4 to 6 in (10 to 15 cm) stub and lift with a fork | Firm heavy rhizomes with visible growing points |
| Winter | Store at 45 to 55F (7 to 13C) in barely damp packing | Monthly check for soft, sour or shriveling pieces |
Early summer: building the plant
This is the growth phase and everything is about not letting the plant check. Water deeply once or twice a week, giving 1 to 2 in (2.5 to 5 cm), and lay a 2 in (5 cm) mulch over the root area once the shoots are well up. Feed with a balanced product every two to three weeks, and keep away from high nitrogen feeds that produce leaves at the expense of flower spikes.
Start weekly pest inspections now rather than waiting for damage. Run a hand up each cane to the tight new spear at the top and look for silk threads, dark frass crumbs, or a spear that has failed to open on schedule. Leaf roller caterpillars live inside those closed leaves, and this is the only stage at which hand removal alone will keep them in check.
Tie tall single specimens to their stakes as they pass 24 in (60 cm), using soft string in a loose figure of eight. Keep the base of the clump clear of weeds and old leaves so air moves through it.
Midsummer to frost: the flowering season
First flowers open roughly 10 to 12 weeks after planting into warm soil. From here the whole job is maintaining the succession. Each cane flowers once and then is finished for good, so walk the clump weekly, find the canes whose heads have no unopened buds left, and cut those canes right down to within 1 in (2.5 cm) of the soil. New spears follow from the rhizome within a week or two.
Keep watering and feeding through the flowering period; a clump in full flower is at its thirstiest and hungriest. Remove individual spent flowers between cane cuts if you want it tidy and to stop seed pods forming, but do not mistake that for the job that actually matters. Remove leaves more than half browned by cutting them at the sheath.
Watch for rust pustules on the undersides of lower leaves in humid weather and take affected leaves off the site. In warm wet spells check the emerging buds for blackening and softness, and cut any affected cane out at the base immediately.
Autumn and winter: shutting down cleanly
Stop feeding about six weeks before your usual first frost and let watering taper off. The plant should be allowed to finish and move its reserves down into the rhizome rather than being pushed into soft late growth that will not survive.
When the first frost blackens the foliage, cut the canes to a 4 to 6 in (10 to 15 cm) stub and take every scrap of stem and leaf out of the bed, because leaf roller overwinters in old canes. Where the ground freezes, fork the clumps up whole within the following week, shake off the soil, cure for three to seven days in a dry airy frost free place, and pack them loose in barely damp shavings at 45 to 55F (7 to 13C). Where it does not freeze, mulch the crowns 4 to 6 in (10 to 15 cm) deep and leave them in place.
Through winter, check the store monthly and remove anything that has turned soft or sour before it spreads.
The four dates worth recording every year
Keep it to a handful of entries and you will actually maintain them. The first is the planting date together with the soil temperature you measured, which tells you next spring whether to wait longer. The second is the date the first shoot appeared, because the gap between the two is the honest verdict on that decision.
The third is the date the first flower opened, and the running count of canes you cut out through the summer. A clump that produced eight or ten replacement canes was healthy; one that produced two was asking to be divided, fed or moved into more sun.
The fourth is the date of the frost that triggered lifting, along with a simple tally in spring of how many rhizomes came through sound, how many rotted and how many shriveled. Rot points to storage that was too damp or too warm, shriveling to storage that was too dry. Two seasons of these four entries will settle almost every canna question you have about your own garden.