Gardening in Slidell-Mandeville-Covington, LA
Every ZIP code in this metro is USDA zone 9a. That is unusual — most metros span several zones — and it means the one number people usually look up is the same wherever you are here.
Your freeze dates
Those are the earliest and latest medians among the 5 stations serving this metro — not an average, and not one station standing in for the rest. Half of years freeze later than a station's own median.
The spread is the point. Even in a metro that is one hardiness zone throughout, its stations disagree about the last spring freeze. Hardiness zone and frost date measure different things — a zone is the average annual coldest night, a freeze date is when the season turns — and a place can be uniform in one and varied in the other. Use the tools below with your own ZIP rather than the ends of this range.
Your growing season
NOAA publishes a growing-season length for each station, and across the 5 stations serving Slidell-Mandeville-Covington, LA it runs 253–281 days . That figure is published, not computed from the two freeze dates — subtracting one from the other gives the wrong answer wherever a season crosses New Year. Mean summer high (June–August) runs 89–92 °F , at or above the 90 °F point where cool-season crops bolt and tomato and pepper pollen fails — so midsummer sowings of lettuce and its relatives are worth holding here.
When to start seeds in Slidell-Mandeville-Covington, LA
Every spring job for 63 crop dates, counted from this metro's own last spring freeze. Each is a range across all 5 stations — the earliest and latest that job falls anywhere in the metro — because no one station speaks for the whole area.
| Crop | Job | When | Offset |
|---|---|---|---|
| Green Onions | Start indoors | January 5 – December 30 | 8 weeks before |
| Peppers | Start indoors | January 5 – December 30 | 8 weeks before |
| Broccoli | Start indoors | January 13 – January 29 | 6 weeks before |
| Cabbage | Start indoors | January 13 – January 29 | 6 weeks before |
| Collards | Start indoors | January 13 – January 29 | 6 weeks before |
| Kale | Start indoors | January 13 – January 29 | 6 weeks before |
| Leaf Lettuce | Start indoors | January 13 – January 29 | 6 weeks before |
| Peas | Direct sow | January 13 – January 29 | 6 weeks before |
| Spinach | Direct sow | January 13 – January 29 | 6 weeks before |
| Sweet Potato | Start indoors | January 13 – January 29 | 6 weeks before |
| Tomatoes | Start indoors | January 13 – January 29 | 6 weeks before |
| Bok Choy | Start indoors | January 20 – February 5 | 5 weeks before |
| Kohlrabi | Start indoors | January 20 – February 5 | 5 weeks before |
| Swiss Chard | Start indoors | January 20 – February 5 | 5 weeks before |
| Arugula | Direct sow | January 27 – February 12 | 4 weeks before |
| Baby Salad Greens | Direct sow | January 27 – February 12 | 4 weeks before |
| Beets | Direct sow | January 27 – February 12 | 4 weeks before |
| Green Onions | Direct sow | January 27 – February 12 | 4 weeks before |
| Mustard Greens | Direct sow | January 27 – February 12 | 4 weeks before |
| Okra | Start indoors | January 27 – February 12 | 4 weeks before |
| Radishes | Direct sow | January 27 – February 12 | 4 weeks before |
| Turnips | Direct sow | January 27 – February 12 | 4 weeks before |
| Cabbage | Set out | February 3 – February 19 | 3 weeks before |
| Carrots | Direct sow | February 3 – February 19 | 3 weeks before |
| Collards | Direct sow | February 3 – February 19 | 3 weeks before |
| Collards | Set out | February 3 – February 19 | 3 weeks before |
| Cucumbers | Start indoors | February 3 – February 19 | 3 weeks before |
| Green Onions | Set out | February 3 – February 19 | 3 weeks before |
| Kale | Direct sow | February 3 – February 19 | 3 weeks before |
| Kale | Set out | February 3 – February 19 | 3 weeks before |
| Kohlrabi | Direct sow | February 3 – February 19 | 3 weeks before |
| Kohlrabi | Set out | February 3 – February 19 | 3 weeks before |
| Leaf Lettuce | Direct sow | February 3 – February 19 | 3 weeks before |
| Pumpkins | Start indoors | February 3 – February 19 | 3 weeks before |
| Summer Squash | Start indoors | February 3 – February 19 | 3 weeks before |
| Winter Squash | Start indoors | February 3 – February 19 | 3 weeks before |
| Zucchini | Start indoors | February 3 – February 19 | 3 weeks before |
| Bok Choy | Direct sow | February 10 – February 26 | 2 weeks before |
| Bok Choy | Set out | February 10 – February 26 | 2 weeks before |
| Broccoli | Set out | February 10 – February 26 | 2 weeks before |
| Cilantro | Direct sow | February 10 – February 26 | 2 weeks before |
| Leaf Lettuce | Set out | February 10 – February 26 | 2 weeks before |
| Swiss Chard | Direct sow | February 10 – February 26 | 2 weeks before |
| Swiss Chard | Set out | February 10 – February 26 | 2 weeks before |
| Dill | Direct sow | February 17 – March 5 | 1 week before |
| Bush Beans | Direct sow | March 3 – March 19 | 1 week after |
| Cucumbers | Set out | March 3 – March 19 | 1 week after |
| Pumpkins | Direct sow | March 3 – March 19 | 1 week after |
| Pumpkins | Set out | March 3 – March 19 | 1 week after |
| Summer Squash | Direct sow | March 3 – March 19 | 1 week after |
| Summer Squash | Set out | March 3 – March 19 | 1 week after |
| Sweet Corn | Direct sow | March 3 – March 19 | 1 week after |
| Tomatoes | Set out | March 3 – March 19 | 1 week after |
| Winter Squash | Direct sow | March 3 – March 19 | 1 week after |
| Winter Squash | Set out | March 3 – March 19 | 1 week after |
| Zucchini | Direct sow | March 3 – March 19 | 1 week after |
| Zucchini | Set out | March 3 – March 19 | 1 week after |
| Cucumbers | Direct sow | March 10 – March 26 | 2 weeks after |
| Okra | Direct sow | March 10 – March 26 | 2 weeks after |
| Okra | Set out | March 10 – March 26 | 2 weeks after |
| Peppers | Set out | March 10 – March 26 | 2 weeks after |
| Southern Peas | Direct sow | March 10 – March 26 | 2 weeks after |
| Sweet Potato | Set out | March 10 – March 26 | 2 weeks after |
The week offsets are conventional extension guidance and vary by variety; the freeze dates they are counted from are measured. For a single date rather than a range, run when do I start my seeds? with your own ZIP code.
What lives through a zone 9a winter
Winter hardiness runs on the zone alone, so this one is exact for the whole of Slidell-Mandeville-Covington, LA rather than a range. Of 74 perennial fruits, nuts, berries, vegetables and herbs, 46 come through a zone 9a winter — and 25 of the failures are not about cold at all, but about winters too mild to break dormancy or summers too hot.
Among them: Elderberry, Horseradish, Sunchoke, Walking Onion, Chives, Mint, American Persimmon, European Plum. See the full list with reasons.
The 5 stations behind these numbers
Every figure above comes from these, and each is named so you can check it. Distances vary by ZIP code, so the tools report yours rather than this page guessing.
| Station | NOAA ID | Last spring freeze | First fall freeze | Season |
|---|---|---|---|---|
| Bogalusa, LA | USC00160945 | March 2 | November 23 | 265 days |
| Covington 4 Nnw, LA | USC00162151 | March 12 | November 18 | 253 days |
| Picayune, MS | USC00226921 | March 9 | November 18 | 255 days |
| Slidell AP, LA | USW00053865 | March 3 | November 21 | 263 days |
| Slidell, LA | USC00168539 | February 24 | December 1 | 281 days |
These are medians, not averages — NOAA publishes freeze dates as a probability distribution, and half of years freeze later than the date shown.
Work out your own dates
Each of these takes a ZIP code and answers for that ZIP alone, citing the station it used and how far away it is. There is a ZIP box in the header of every page.
- What survives my winter?
Runs on the hardiness zone, so it answers for all of Slidell-Mandeville-Covington, LA at once — zone 9a across 74 perennial fruits, berries, vegetables and herbs.
- When do I start my seeds?
Dates every spring job from your own last freeze — sow indoors, set out, direct sow.
- When do I sow the next round?
How often each crop is worth re-sowing, and when the next sowing is due.
- What can I still plant?
Counts the growing days left before your first fall freeze, crop by crop.
Where these numbers come from
The hardiness zone is the USDA 2023 Plant Hardiness Zone Map, published per ZIP code by PRISM at Oregon State. The freeze dates are NOAA's 1991–2020 Climate Normals, read from every station whose normals cover a ZIP code in this metro. Nothing here is estimated, and no station stands in for another.
This page names no single station on purpose. Picking one to represent a metro sounds reasonable and is not: the station serving the most ZIP codes is an artifact of where ZIP centroids happen to fall, and it selects a lock on the Monongahela for Pittsburgh and a far southern suburb for Chicago. A range across every station is true; a single cited date for a whole metro is not.