September 2026.

Bring the harvest in

• Save seeds from self-pollinating flowers

  Marigolds, cosmos, sunflowers, zinnias — dry seed heads on the plant, then collect, label, and store in glass jars. Free plants next spring.

• Pot up herbs to bring indoors

  Basil, parsley, and thyme in pots on a bright windowsill extend the fresh-herb season through winter. Basil is short-lived indoors; parsley and thyme go months.

• Bring houseplants back inside

  Blast every plant with the hose to knock off aphids and spider mites before they come in. Skip this and you'll be dealing with an infestation by December.

The Persephone deadline

• Anything you want to eat in December must be near-mature by November 20

  After Nov 20, daylight in Hunterdon drops below 10 hours a day and plant growth virtually stops. The fall crops don't die; they hold at whatever size they've reached. Cover them and you're 'storing them in the garden.' Miss the mid-November target and you're growing them for spring — see the Fall Garden Planning guide for the full framework.

• Drop row cover on the first frost warning

  Row cover installed over the low tunnel hoops in August pays off now. Semi-hardy crops (lettuce, chard, broccoli) get another 3–4 weeks under Agribon-19. Hardy crops (kale, spinach, mâche) go into December.

• Last-chance direct sow: greens only, before September 15

  Anything sown after mid-September has to be a fast-growing cold-hardy green — arugula, spinach, mâche, tatsoi, mizuna. Everything else needs more time than the sun will give it.

Building for next year

• Top up beds with compost

  Every year takes a little out of the soil. Every year, a topdressing of compost puts a little back. Do this now so it works in over winter.

• Divide spring-flowering perennials

  Peonies, iris, phlox — anything that blooms in spring or early summer gets divided in fall. Fall bloomers wait until spring.

• Get cover crops in by mid-month

  Winter rye and hairy vetch protect empty beds through winter and add nitrogen back to the soil. Sow no later than the 20th so the seed germinates before it gets too cold.

• Plant new trees and shrubs

  Cool air, warm soil, autumn rains — the perfect trifecta for root establishment. Plant now and by spring the tree is already settled.

• Plant grass seed

  September is the best month of the year to seed a lawn. Cooler days, warm soil, less crabgrass pressure. Water lightly and daily until germination.