When to Plant Sweet Alyssum in Coos County, NH
This month in Coos County, New Hampshire
Here's what deserves your attention in Coos County, New Hampshire this month. Everything below is tailored to Zone 4b and timed around your local frost dates.
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It's harvest week for sweet alyssum
If you can't use it all right away, check the food-preservation section of your planner.
Coming up in July — start thinking about
- Starting indoors: sweet alyssum
- First harvests: sweet alyssum
Sweet Alyssum (Lobularia maritima) is a low-growing cool-season annual prized for its honey-scented clusters of tiny white, pink, or purple flowers. A workhorse border plant, it tolerates light frost, self-seeds readily, and attracts beneficial insects throughout its bloom season. In warm climates it often re-blooms in fall after summer heat fades.
Coos County, New Hampshire is in USDA Zone 4b. The average last spring frost is May 18 and the first fall frost is September 30, giving you a growing season of approximately 135 days.
At an elevation of 604 feet, Coos County receives approximately 40.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Sweet Alyssum to ensure they mature before fall.
Coos County Soil Profile
Soil Type
Silt Loam
Soil pH
5.2-6.6
Drainage
Well Drained
Sweet Alyssum Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Soil Compatibility in Coos County
How your county's soil matches Sweet Alyssum's growing requirements.
Soil pH
Your soil pH (5.2–6.6) is more acidic than Sweet Alyssum prefers (6.0–7.5). Add garden lime to raise pH.
Soil Texture
The silt loam soil in Coos County is excellent for Sweet Alyssum — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.4%). Annual compost additions will help Sweet Alyssum.
How to Plant Sweet Alyssum
Succession Planting Sweet Alyssum
Sow every 5.1 weeks. Last sowing by Aug 01 to harvest before frost.
Sweet Alyssum Water Budget
Monthly Watering Guide for Sweet Alyssum
Sweet Alyssum needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Sweet Alyssum Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 3.2" | 0" | ❄️ Dormant |
| Feb | — | 2.9" | 0" | ❄️ Dormant |
| Mar | — | 2.9" | 0" | ❄️ Dormant |
| Apr | — | 3.4" | 0" | ❄️ Dormant |
| May | 2.2" | 3.6" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 3.5" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 3.9" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 4" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 3.7" | 0" | ✅ Rainfall sufficient |
| Oct | — | 3.1" | 0" | ❄️ Dormant |
| Nov | — | 3.1" | 0" | ❄️ Dormant |
| Dec | — | 3.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Coos County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Sweet Alyssum Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Sweet Alyssum Planting Timeline — Coos County, NH
Sweet Alyssum Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 30 | Mar 30 – Apr 13 |
| Transplant Outdoors | May 18 | May 18 – Jun 1 |
| Direct Sow | May 11 | May 11 – Jun 1 |
| Bloom | June 29 | Jun 29 – Aug 31 |
· 6" apart · Rows 8" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors |
| May | Transplant Outdoors Direct Sow |
| June | Transplant Outdoors Direct Sow Bloom |
| July | Bloom |
| August | Bloom |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
45–60 days
🧪 Soil pH
Needs 6–7.5 · Your soil: too_acidic
🗺️ USDA Zone
Zone 4b
📆 Growing Season
135 days in Coos County
Growing Tips for Sweet Alyssum in Coos County
Direct sow Sweet Alyssum outdoors after May 18 in Coos County when soil has warmed and frost danger has passed.
Common pests for Sweet Alyssum in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
General growing tips
Surface-sow seeds — they need light to germinate. Direct-sow as soon as soil can be worked in spring; in zones 7+ also sow in fall. Thin to 6 inches apart. Shear back hard in midsummer when heat causes dormancy — plants recover and re-bloom when cool weather returns. Self-seeds prolifically; allow a few plants to set seed for a perpetual colony.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Sweet Alyssum in Other Locations
Frequently Asked Questions
When should I plant Sweet Alyssum in Coos County, NH?
Coos County is in Zone 4b with an average last frost of May 18. Plan your Sweet Alyssum planting based on this frost date — see the calendar above for exact timing.
What planting zone is Coos County, NH?
Coos County, New Hampshire is in USDA Hardiness Zone 4b. The average last spring frost is May 18 and first fall frost is September 30.
Your Coos County Garden Planner — Free
A 22-page printable planner built for Coos County (Zone 4b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.