Mallow Growing Calendar: Sowing, Flowering, Rust and the Seed Decision

The year at a glance

Mallow runs on a simple annual cycle whether it behaves as an annual, a biennial or a short-lived perennial on your site. The plant builds a rosette and a taproot, throws up flowering stems, flowers heavily for six to eight weeks, sets seed, and dies back. Rust runs on its own clock alongside it, arriving in early summer and worsening steadily.

The table below is the whole season in order. Everything else in this guide is detail on one of these rows.

Spring: sow, thin, pinch

Wait for the soil rather than the calendar. Mallow sown into cold ground sits still and gets eaten; sown two weeks later into soil above 55F (13C) it overtakes the earlier sowing within a month. Take the reading in the morning, two inches (5 cm) down.

Once the seedlings are up, the spring jobs are thinning and one pinch. Both are quick, both are easy to postpone, and both cost you a noticeably worse plant if you skip them.

1. Prepare poor ground, not rich ground Fork the bed over, break up any pan so the taproot can get down, and add nothing. Skip the compost and skip the manure. Mallow flowers best and stands upright in soil you would consider ordinary.
2. Scarify and sow direct Sandpaper or soak the seed overnight, then sow two seeds per station a quarter inch (6 mm) deep, stations two feet (60 cm) apart. Water once thoroughly and then let the surface dry between waterings.
3. Thin in two passes Down to six inches (15 cm) apart at the true-leaf stage, then to the final two feet (60 cm) at four to six inches tall. Keep the stocky seedlings, not the tall ones.
4. Pinch at eight to ten inches Take out the top inch (2.5 cm) of the leading shoot before any bud shows. This gives four or five even stems from low on the plant instead of one dominant stem.

Protect seedlings from flea beetle with fine mesh until they have six true leaves. Past that size nothing much troubles a mallow, and the mesh comes off for good.

Early summer: the rust clock starts

This is the quiet stretch that decides how the rest of the season goes. The plant is growing fast, there is nothing obviously to do, and rust is establishing on the lowest leaves where you are not looking.

Two habits from the point the plant reaches knee height: strip the bottom six to eight inches (15 to 20 cm) of foliage and keep it clear, and turn over the lowest leaves once a week to check for orange pustules. Ten minutes a week here is worth more than anything you can do in midsummer.

Midsummer: pick daily, then cut back

The flowering flush is short and heavy. If you want tea flowers, this is a daily job: pick newly opened blooms in the morning once the dew has gone and get them onto the drier within the hour. Picking is also deadheading, which keeps the plant flowering rather than diverting into seed.

When roughly three quarters of the flowers on a stem have gone over, cut that stem back by a third to a half, to just above a healthy pair of leaves. Work stem by stem over a week or two so that something is always in flower. New shoots break within a fortnight and carry a lighter second flush.

1. Pick in the morning, into a shallow tray Take flowers on their first or second day open, after the dew has dried and before the sun is high. One layer deep, out of the sun, straight to the drier.
2. Deadhead whatever you do not pick Every flower you leave becomes a seed head, and every seed head is next year's volunteers. Snap the spent flowers off behind the calyx as you go along the row.
3. Cut back stem by stem Shorten each stem by a third to a half once its flowers are mostly over, cutting a quarter inch (6 mm) above a healthy pair of leaves. Take the rustiest stem out at ground level entirely.
4. Do not feed the regrowth The regrowth comes freely without help. Feeding it produces soft, rust-prone shoots and a plant that splits at the base in the first late-summer storm.

Expect two to three weeks from cut back to the first new flower. Count backward from your first expected frost: a cut back too late in the season simply removes the flowers you already had and gives you nothing in return.

Late season: the seed decision, then the clear-up

The last flush is where mallow decides whether it is a plant or a problem. Left standing, the seed heads ripen, shatter and populate the bed for years. The decision has to be deliberate and it has to be made before the discs turn tan.

Then the clear-up, which is the other half of rust control. Cut every stem to the ground after the first hard frost, rake out all fallen leaves, and bin the lot. Old stems and leaves left over winter carry the spores straight into next season, and a bed cleared properly starts several weeks cleaner.

Mallow may come back from the crown for a second or third year in a mild climate, or die out after flowering in a colder one. Either way the autumn clear-up is the same, and it is worth keeping a few saved seeds regardless of whether you expect the plant to return.

The dates worth writing down

Six figures cover the whole mallow year, and they are stable enough on the same site that a single season of records makes the next one substantially easier to run.

Keep them somewhere you will actually look at next spring, alongside a sketch of where the plants stood. Position matters as much as date with mallow, because both the rust and the volunteers are tied to specific spots in the bed.